Bio/Biochem II Flashcards
(681 cards)
1
Q
If a lung is punctured, what effect will this likely have on breathing?
A
The punctured lung will be unable to inflate, affecting inhalation
2
Q
What is a statement that can explain why lung volume never drops below 15 ml/kg?
A
The residual volume is such that the lungs are at their minimum volume under maximum intrapleural pressure
3
Q
Which of the following best explains why a Robertsonian carrier may have no health problems due to his or her chromosome rearrangement?
A
Genes on the lost p arms can be found elsewhere in the genome
4
Q
How many chromosomes are found in a liver cell of a Robertsonian translocation carrier?
A
45 (short arms of 2 fused chromosomes is usually lost)
5
Q
The Km for a Michaelis-Menten plot is:
A
The SUBSTRATE concentration at half of Vmax
6
Q
Histone deacetylation of lysine results in:
A
decreased gene expression
7
Q
Histone acetylation of lysine results in:
A
increased gene expression
8
Q
The N and C termini are:
A
N = positive, C = negative
9
Q
Where are post-transcriptional modifications carried out?
A
Within the nucleus
10
Q
If the DNA of a representative species from each of the major kingdoms was examined, the sequences for what would be similar?
A
DNA synthesis
11
Q
What are some molecules that have an atom with sp2-type hybridization?
A
Carbon dioxide, carbonate, formaldehyde
12
Q
If it says something lacks introns…
A
It has a bacterial origin
13
Q
What are transmembrane proteins made of?
A
Glycoproteins
14
Q
Which components of cells are physically connected by a gap junction?
A
The cytoskeleton of one to the cytoskeleton of the other
15
Q
Cardiac disorders involving gap junction dysfunction would most likely manifest clinically through:
A
Arrhythmia
16
Q
Why are chemical synapses slower than electrical synapses?
A
Chemical synapses require the movement of agents through intercellular space
17
Q
What type of control does siRNA exert on an enzyme?
A
Post-transcriptional control (due to its structure, siRNA is only able to bind to other RNA strands, not to DNA or protein)
18
Q
Meiosis I results in:
A
2 haploid cells with 23 chromosomes, each chromosome consisting of 2 sister chromatids (sister chromatids remain attached)
19
Q
Given that delta G is negative for a particular reaction, what can be said about the equilibrium constant K?
A
K > 1
20
Q
The concentration of intracellular signaling molecules fluctuates rapidly in dividing cells during the cell cycle. Which of the following experimental techniques would be best to elucidate the mechanism of regulation for these proteins?
A
Western blot and RT-PCR
21
Q
For a reaction with a Keq, a change in temperature could:
A
Increase or decrease the rate of one molecule to another
22
Q
ATP is not required for:
A
Spontaneous reactions
23
Q
Which of the following molecules is/are most likely to have selective proteins in the BBB to facilitate its passage into the brain?
A
Amino acids
24
Q
What are some functions of the blood-brain barrier?
A
Protection of brain from bodily hormones, maintenance of a stable chemical equilibrium for the brain, and allowing of more glucose to enter the btrain than any other tissue
25
If pharmacologists wished to convert morphine into a form available to brain tissue, which of the following changes could be made to its molecular structure to allow for the best chance to use the drug as a direct brain treatment?
Replace the alcoholic protons with acetyl groups
26
Folate is a common supplement given to pregnant women to prevent neural tube defects. The most likely reason is:
Folate plays a role in ectodermal induction
27
What is skeletal muscle?
Striated, always polynucleated, voluntary
28
What is smooth muscle?
Always uninucleated, innervated by the autonomic nervous system, exhibit myogenic activity
29
What is cardiac muscle?
Striated, innervated by the autonomic nervous system, exhibit myogenic activity, can be uninucleated or binucleated
30
Which zone or band in the sarcomere does NOT change its length during muscle contraction? Why?
A-band; it is the entire length of the myosin filament
31
What are the events that initiate muscle contraction, in order? Start with neurotransmitter release and trace the pathway to the point where myosin binds with actin.
Release of acetylcholine from motor neuron -> activation of acetylcholine receptors in sarcolemma -> depolarization of sarcolemma -> spreading of signal using T-tubules -> release of calcium from sarcoplasmic reticulum (SR) -> binding of calcium to troponin -> conformational shift in tropomyosin -> exposure of myosin-binding sites -> myosin binds to actin
32
What role does the binding of ATP to the myosin head place in the cross-bridge cycle? What about the dissociation of ADP and inorganic phosphate from the myosin head?
ATP binding allows the myosin filament to disconnect from actin, dissociation from ADP and inorganic phosphate causes the powerstroke (upon attachment of actin, the myosin head snaps back to a low energy position and moves the actin filament toward the center of the sarcomere)
33
What is tetanus?
The summation of multiple simple twitches that occur too quickly for the muscle to relax, leads to a stronger and more prolonged contraction of the muscle
34
What is the difference between compact and spongy bone?
Compact bone = dense, used for its strength; forms most of the outer layers of a bone, Spongy bone = has many spaces between bony spicules called trabeculae, is the site of marrow production; is found in the interior core of the bone, helps distribute forces or pressures on the bone
35
What are the three structural parts of a bone? Which part contributes most to linear growth?
Diaphysis, metaphysis, epiphysis (where growth plates are found, contribute to linear growth)
36
What chemical forms most of the inorganic component of bone?
Hydroxyapatite crystals
37
What are the functions of osteoblasts, osteoclasts, and chondrocytes?
Osteoblasts build bone, osteoclasts break down bone, chondrocytes form cartilage
38
What liquid provides the lubrication for movable joints? What tissue produces it?
Synovial fluid, produced by the synovium, lubricates movable joints
39
With which of the following molecules does Ca2+ bind after its release from the sarcoplasmic reticulum to regulate muscle contraction?
Troponin
40
When the knee moves back and forth during walking, what prevents the surfaces of the leg bones from rubbing against each other?
Articular cartilage
41
What are some true statements about the periosteum?
Serves as a site of attachment of bone to muscle, cells of the periosteum may differentiate into osteoblasts, and the periosteum is a fibrous sheath that surrounds long bones
42
To facilitate the process of birth, an infant's head is somewhat flexible. This flexibility is due in part to the two fontanelles, which are soft spots of connective tissue in the infan't skull. With time, the fontanelles will close through a process known as:
Intramembranous ossification
43
What does it mean for an allele to be dominant? Recessive?
Requires only one copy for expression; requires two copies for expression
44
What does it mean for a genotype to be homozygous? Heterozygous? Hemizygous?
Homozygous = 2 alleles are the same, heterozygous = 2 alleles are different, hemizygous = only 1 allele is present for a given gene
45
What is the difference between complete dominance, codominance, and incomplete dominance?
Complete dominance = one allele masks the expression of the other, codominance = a gene has more than 1 dominant allele, incomplete dominance = a gene has no expressed alleles, heterozygotes have phenotypes that are intermediate between homozygotes
46
What is the difference between penetrance and expressivity?
Penetrance = the proportion of the population that expresses a phenotype, given a particular genotype; Expressivity = the differences in expression of a phenotype in individuals
47
With which phase of meiosis does each of Mendel's laws most closely correlate?
Mendel's first law (Law of Segregation) = Anaphase I; Mendel's second law (Law of Independent Assortment) = Prophase I
48
Why would genetic leakage in animals be rare prior to the last century?
Genetic leakage requires the formation of a hybrid organism that can then mate historically, so fertile hybrids were certainly rare before a more modern understanding of genetics
49
Why is genetic drift more common in small populations? What relationship does this have to the founder effect?
Genetic drift occurs due to chance, so its effects will be more pronounced with a smaller sample size; the founder effect occurs when a small group is reproductively isolated from the larger population, allowing certain alleles to take on a higher prevalence in the group than in the rest of the population
50
All five criteria of the Hardy-Weinberg principle are required to imply what characteristic of the study population?
The criteria for the Hardy-Weinberg principle all imply that the study population is not undergoing evolution; thus, the allele frequencies will remain stable over time
51
What is natural selection?
Certain traits that arise from chance are more favorable for reproductive success in a given environment, and that those traits will be passed on to future generations
52
What is the modern synthesis model?
Natural selection is for specific alleles, which are passed on to future generations through formation of gametes; the alleles for these favorable traits arise from mutations
53
What is inclusive fitness?
The reproductive success of an organism is not only due to the number of offspring it creates, but also the ability to care for young (explains changes based on survival of hte species)
54
What is punctuated equilibrium?
For some species, little evolution occurs for a long period, which is interrupted by rapid bursts of evolutionary change
55
If a male with hemophilia (XhY) is crossed with a female carrier of both color blindness and hemophilia (XcXh), what is the probability that a female child will be phenotypically normal?
0.5
56
What are some true statements based on Darwin's theory of evolution?
Natural selection is the driving force for evolution, natural selection can drive organisms living in groups to ultimately become distinct species, and fitness is measured by reproductive success
57
What are some necessary conditions for Hardy-Weinberg equilibrium?
(1) No change in the DNA sequence, (2) No migration, (3) A very large population size, (4) Random mating, and (5) No natural selection
58
What is DNA methyltransferase?
An enzyme responsible for catalyzing the methylation (and therefore silencing) of DNA
59
If a disease is an X-linked recessive disorder:
A woman must have a mutated copy of the gene on both of her X chromosomes in order to express the trait
60
In the ETC, are electron carriers mobile and hydrophobic?
No
61
What is observed in a patient experiencing hyperventilation?
Net exhalation of CO2, increased blood pH, increased hemoglobin O2 affinity
62
Between folic acid, carbonic acid, ascorbic acid, and citric acid, which is not an organic acid?
Carbonic acid (because no covalent bond between carbon and hydrogen)
63
Conn's syndrome, also known as primary hyperaldosteronism, is most likely to cause which symptom?
Low blood potassium (Aldosterone = increases Na+ reabsorption and K+ secretion)
64
What are some post-transcriptional modifications that are involved in the life cycle of a virus?
Splicing and polyadenylation
65
Viruses are directly involved in which of the following processes in bacteria?
Transduction (foreign DNA is introduced into the cell by a viral vector)
66
What interaction would exist between 2 intra-subunit molecules?
Ion-dipole interactions
67
In an adult, which of the following cell types is LEAST likely to enter a programmed G0 phase of the cell cycle?
Epithelial cells
68
Viruses are distinct from most biological organisms in that they:
Are pathogenic entities which have been described as not being "living"
69
A disruption in the regulation of which cellular process is probably responsible for keloids?
Mitosis
70
Malonyl-CoA is an intermediate in cytosolic fatty acid biosynthesis. Its inhibition of the B-oxidation of long-chain fatty acids:
Prevents the degradation of newly synthesized fatty acids
71
For methylation and deamination:
a pyrimidine cannot be converted to a purine and vice versa
72
Which base is heavier: thymine or uracil?
Thymine
73
What are a few examples of aprotic solvents?
Acetone, DMSO
74
What are a few examples of protic solvents?
Water, methanol
75
What is the function of ligase during S-phase?
Binds together pieces of the lagging strand
76
What is passive immunity?
The transfer of active humoral immunity in the form of ready-made antibodies, from one individual to another
77
What is natural immunity?
Immunity that is present in the individual at birth, prior to exposure to a pathogen or antigen (skin, salivary enzymes, neutrophils, natural killer cells, complement)
78
What is cell-mediated immunity?
An immune response that does not involve antibodies, but involves the activation of phagocytes, antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen
79
What is innate (non-specific) immunity?
Includes anatomical barriers, secretory molecules, and cellular components
80
If splicing took place in a virus...
It is a DNA virus
81
What is a structure found in the blood-brain barrier?
Tight junctions
82
What would be useful in cellular movement?
Flagella, cilia, actin polymerization
83
What are the four fundamental tenets of the cell theory?
All living things are made of cells, the cell is the basic functional unit of life, all cells arise from other cells, and genetic information is carried in the form of DNA and is passed from parent to daughter cell
84
What is the function of the nucleus?
Stores genetic information and is the site of transcription
85
What is the function of the mitochondria?
Involved in ATP production and apoptosis
86
What is the function of the lysosome?
Break down cellular waste products and molecules ingested through endocytosis, and is involved in apoptosis
87
What is the function of the rough ER?
Synthesizes proteins destined for secretions
88
What is the function of the smooth ER?
Lipid synthesis and detoxification
89
What is the function of the Golgi apparatus?
Packages, modifies, and distributes cellular products, transport of lipids, creation of lysosomes
90
What is the function of the peroxisome?
Break down very long chain fatty acids, synthesize lipids, and contribute to the pentose phosphate pathway
91
What would be the outcome of a deficiency in the production of hydrogen peroxide?
An inability to digest very long chain fatty acids
92
What are microfilaments composed of?
Actin
93
What are microtubules composed of?
Tubulin
94
What are intermediate filaments composed of?
Keratin
95
How do the cytoskeletal structures of centrioles and flagella differ?
Centrioles = 9 triplets of microtubules around a hollow center, flagella = 9 doublets on the outside, with two microtubules on the inside
96
How is Archaea similar to bacteria/eukaryotes?
Archaea's similarities to bacteria: single-celled organisms that lack a nucleus or membrane-bound organelles, contain a single circular chromosome, divide by binary fission or budding; Archaea's similarities to eukaryotes: start translation with methionine, contain similar RNA polymerases, contain DNA associated with histones
97
How do the structures of eukaryotic and prokaryotic flagella differ?
Eukaryotic flagella = microtubules composed of tubulin, organized in a 9+2 arrangement ; bacterial flagella = made of flagellin and consist of a filament, basal body, and hook
98
What is transformation?
The acquisition of exogenous genetic material that can be integrated into the bacterial genome
99
What is conjugation?
The transfer of genetic material from one bacterium to another across a conjugation bridge, from F+ to F- cells, or a portion from an Hfr cell to a recipient
100
What is transduction?
The transfer of genetic material from one bacterium to another by a bacteriophage
101
What are the four phases of the bacterial gorwth curve and the features of each phase?
Lag phase, exponential phase, stationary phase, death phase
102
What does an enveloped, single-stranded positive-sense RNA virus mean?
The virus contains an outer layer of phospholipids with an inner capsid. Within the capsid, there is single-stranded RNA that can be immediately translated to protein by the ribosomes of the host cell
103
Describe the pathway of retroviral nucleic acids from infection of a host cell to release of viral progeny.
Enters as single-stranded RNA, undergoes reverse transcription to form double-stranded DNA, DNA enters the host genome and replicates with the host cell, DNA transcribed to mRNA to be used to make structural proteins, mRNA doubles as viral genome for new virions, once new virions are assembled they can be released to infect other cells
104
What is the difference between the lytic and lysogenic cycles?
Lytic cycle = bacteriophages replicate in the host cell in extremely high numbers until the host cell lyses and releases the virions; lysogenic cycle = the bacteriophage genome enters the host genome and replicates with the host cell as a provirus
105
What are some examples of connective tissues?
Cartilage, ligaments, adipose tissue, blood
106
What types of nucleic acids could form the genome of a virus?
Single-stranded RNA, double-stranded DNA, single-stranded DNA
107
What occurs in the Golgi apparatus?
Modification and distribution of proteins
108
What is a statement that correctly describes HSV?
Herpes simplex virus adds its genetic information to the genetic information of the cell
109
What can account for a bacterium's ability to increase its genetic variability and thus adapt itself to resist different antibiotics?
Conjugation and transduction
110
After infectoin of a cell, a viral particle must transport itself to the nucleus in order to produce viral proteins. What is the likely genomic content of the virus?
Double-stranded DNA
111
What occurs during G1 phase?
Cell grows and performs its normal functions. DNA is examined and repaired.
112
What occurs during S phase?
DNA is replicated.
113
What occurs during G2 phase?
Cell continues to grow and replicates organelles in preparation for mitosis. Cell continues to perform its normal functions.
114
What occurs during M phase?
Mitosis (cell division) occurs.
115
What occurs during G0 phase?
The cell performs its normal functions and is not preparing to divide.
116
What occurs during prophase?
Chromosomes condense, nuclear membrane dissolves, nucleoli disappear, centrioles migrate to opposite poles and begin forming the spindle apparatus
117
What occurs during metaphase?
Chromosomes gather along the metaphase plate in the center of the cell under the guidance of the spindle apparatus
118
What occurs during anaphase?
Sister chromatids separate, and a copy of each chromosome migrates to opposite poles
119
What occurs during telophase?
Chromosome decondense, nuclear membrane reforms, nucleoli reappear, spindle apparatus breaks down, cell divides into two identical daughter cells
120
What is the ploidy of the daughter cells produced from meiosis I? From meiosis II?
After meiosis I = two haploid daughter cells; after meiosis II = up to four haploid gametes
121
What is the difference between between homologous chromosomes and sister chromatids?
Homologous chromosomes = related chromosomes of opposite parental origin; Sister chromatids = identical copies of the same DNA that are held together at the centromere
122
What are the functions of interstitial cells of Leydig and Sertoli cells?
Interstitial cells of Leydig = secrete testosterone and other male sex hormones (androgens); Sertoli cells = nourish sperm during their development
123
During which phase of meiosis is a primary oocyte arrested? During which phase of meiosis is a secondary oocyte arrested?
A primary oocyte is arrested in prophase I; a secondary oocyte is arrested in metaphase II
124
What is an acrosome and what organelle forms from it?
Acrosome (modified Golgi apparatus) = contains enzymes that are capable of penetrating the corona radiata and zona pellucida of the ovum, permitting fertilization to occur
125
Which hormones are key to sexual differentiation in a fetus with XY genotype? Describe the expected phenotype if receptors to these hormones are absent?
Androgens lead to male sexual differentiation (absence of androgen receptors leads to an XY genotype)
126
Which of the following is the correct sequence of the development of a mature sperm cell?
Spermatogium -> primary spermatocyte -> secondary spermatocyte -> spermatid -> spermatozoan
127
In patients with Alzheimer's disease, there is a defect in the way the sprindle apparatus attaches to the kinetochore fibers. At which stage of mitotic division would one first expect to be able to visualize this problem?
Prophase (spindle apparatus interacts with kinetochore at end of prophase)
128
A physician who diagnoses a granulosa cell tumor (excessive estrogen) should look for a secondary cancer in which of the following parts of the reproductive tract?
Endometrium (estrogen thickens endometrial lining)
129
Upon ovulation, the oocyte is released into the:
Abdominal cavity
130
At which points in the cell cycle would chemotherapy prevent cell division?
S stage, prophase, or metaphase
131
What contributes to genetic variability?
Random fertilization of an egg by a sperm, random segregation of homologous chromosomes, crossing over between homologous chromosomes during meiosis
132
What is a key difference between mitosis and meiosis?
During metaphase of mitosis, centromeres are present directly on the metaphase plate; during metaphase of meiosis I, there are no centromeres on the metaphase plate
133
What is a component of prophase?
The nucleoli disappear
134
An individual who is phenotypically female is found to have only one copy of a disease-carrying recessive allele on the X chromosome, yet she demonstrates all of the classic symptoms of the disease. Geneticists determine she has a genotype that likely arose from nondisjunction of one of her parents. What is the likely genotype of this individual?
45,X (one copy of recessive allele = no dominant allele)
135
During which phase of the menstrual cycle does progesterone concentration peak?
Luteal phase
136
What would be seen during pregnancy?
High levels of hCG in the first trimester, high levels of progesterone throughout the pregnancy, low levels of FSH in the first trimester
137
What is the difference between determinate and indeterminate cleavage?
Determinate cleavage = cell division that results in cells having definitive lineages (at least one daughter cell is programmed to differentiate into a particular cell type); indeterminate cleavage = cell division that results in cells that can differentiate into any cell type (or a whole organism)
138
From zygote to gastrula, what are the various stages of development?
Zygote -> 2-, 4-, 8-, and 16-cell embryo -> morula -> blastula (blastocyst) -> gastrula
139
During which stage of development does implantation occur?
The blastula (blastocyst) stage
140
What are the primary germ layers, and what organs are formed from each?
Ectoderm (epidermis, hair, nails, epithelia of nose, mouth, anal canal), lens of eye, nervous system, adrenal medulla, inner ear; Mesoderm (musculoskeletal system, circulatory system, excretory system, gonads, muscular and connective tissue layers of digestive and respiratory systems, adrenal cortex); Endoderm (epithelial linings of digestive and respiratory tracts, parts of liver, pancreas, thyroid, bladder, distal urinary and reproductive tracts)
141
What is induction and how does it influence development?
The process by which nearby cells influence the differentiation of adjacent cells, ensures proper spatial location and orientation of cells that share a function or have complementary functions
142
What tissues do neural crest cells develop into?
Peripheral nervous system
143
What is the difference between determination and differentiation?
Determination = the commitment of a cell to a particular lineage; differentiation = the actual changes that occur in order for the cell to assume the structure and function of the determined cell type
144
What are the three types of potency? What lineages can a cell of each type differentiate into?
Totipotency = any cell type in the developing embryo or in extraembryonic tissues; pluripotency = any cell type in the developing embryo; multipotency = any cell type within a particular lineage
145
What are the four types of cell-cell communication?
Autocrine (signal acts on same cell that secreted it); paracrine (signal acts on local cells); juxtracrine (cell triggers adjacent cells through direct receptor stimulations); endocrine (signal travels via the bloodstream to act on cells at distant sites)
146
What is the difference between apoptosis and necrosis?
Apoptosis = programmed cell death and results in contained blebs of the dead cell that can be picked up and digested by other cells ; necrosis = cell death due to injury and results in spilling of cytoplasmic contents
147
What is the oxygenation status of the blood in the umbilical arteries/umbilical vein?
Umbilical arteries carry deoxygenated blood, umbilical vein carries oxygenated blood
148
What are the three fetal shunts? What vessels or heart chambers do they connect? What organ does each shunt bypass?
1) Foramen ovale (connects right atrium to left atrium, bypasses lungs); 2) Ductus arteriosus (connects pulmonary artery to aorta, bypasses lungs); 3) Ductus venosus (connectus umbilical vein to inferior vena cava, bypasses the lungs)
149
What are some of the key developmental features of each trimester?
1st trimester: organogenesis (development of heart, eyes, gonads, limbs, liver, brain); 2nd trimester: tremendous growth occurs, movement beings, face becomes distinctly human, the digits elongate; 3rd trimester: rapid growth and brain development continue, there is transfer of antibodies to the fetus
150
What occurs in each of the three phases of birth?
1st phase: cervix thins out and amniotic sac ruptures; 2nd phase: uterine contractions, coordinated by prostaglandins and oxytocin, result in birth of fetus; 3rd phase: placenta and umbilical cord expelled
151
Which of the following developmental stages has the greatest nuclear-to-cytoplasmic ratio?
Blastula
152
Which of the following is likely to be found in maternal blood during pregnancy?
Progesterone produced by placental cells
153
A cancer cell is removed from a patient and cultured. The cells in this culture seem to be able to divide indefinitely with no cellular senescence. Which protein is likely activated in these cells that accounts for this characteristic?
Telomerase (synthesizes telomeres, which counteracts shortening during replication)
154
What is true about adult stem cells?
Less controversial than embryonic stem cells, require treatment with various transcription factors, reduced risk of rejection if the patient's own stem cells are used
155
A child is born with an imperforate anus, in which the anal canal fails to form correctly and the rectum is not connected to the outside world. This pathology is:
Apoptosis
156
Following a myocardial infarction, the heart often heals by the creation of a scar by fibroblasts. This is an example of:
Incomplete regeneration
157
Which of the following shows the correct order of early developmental milestones during embryogenesis?
Morula -> blastula -> gastrula
158
A pregnant woman is accidentally given a single dose of a teratogenic drug late in the third trimester. The baby is born three days later. Which of the following is the most likely outcome?
Respiratory distress at birth, but no long-term effects (disturb embryo/fetus)
159
What are some true statements about fetal circulation?
More arteries than veins in the umbilical cord, foramen ovule is the only shunt that connects the two chambers of the heart, ductus venosus is the only shunt that bypasses the liver
160
What is an axon?
Transmits an electrical signal (the action potential) from the soma to the synaptic knob
161
What is an axon hillock?
Integrates excitatory and inhibitory signals from the dendrites and fires an action potential if the excitatory signals are strong enough to reach threshold
162
What is a dendrite?
Receive incoming signals and carry them to the soma
163
What is a myelin sheath?
Acts as insulation around the axon and speeds conduction
164
What is a soma?
The cell body and contains the nucleus, endoplasmic reticulum, and ribosomes
165
What is a synaptic bouton?
Lies at the end of the axon and releases neurotransmitter
166
What is a collection of cell bodies in the CNS?
Nucleus
167
What is a collection of cell bodies in the PNS?
Ganglion
168
Which two types of glial cells, if not properly functioning, will make an individual most susceptible to a CNS infection?
Astrocytes (nourish neurons, form blood-brain barrier, helps protect brain from foreign pathogens gaining entrance), microglia ingest and break down waste products and pathogens
169
Guillain-Barre syndrome (GBS) is an autoimmune disease that causes demyelination in the peripheral nervous system. What type of glial cell is being targeted in GBS?
Schwann cells
170
What neural structure initiates the action potential?
Axon hillock
171
What entity maintains the resting membrane potential? What is the approximate voltage of the resting membrane potential?
Is -70 mV, maintained by K+Na+ ATP-ase
172
What is the difference between temporal and spatial summation?
Temporal summation = integration of muliple signals close to each other in time; spatial summation = integration of multiple signals close to each other in space
173
During the action potential, which ion channel opens first? How is this ion channel regulated? What effect does the opening of this channel have on the polarization of the cell?
Na+ channel opens first (around -50 mV), regulated by inactivation which occurs around +35 mV (can only be reversed by repolarizing the cell), opening of Na+ channel causes depolarization
174
During the action potential, which ion channel opens second? How is this ion channel regulated? What effect does the opening of this channel have on the polarization of the cell?
K+ channel opens second (around +35 mV), regulated by closing at low potentials around -70 mV, opening of K+ channels causes repolarization, and eventually hyperpolarization
175
What is the difference between the absolute and relative refractory period?
Absolute refractory period = the cell is unable to fire an action potential regardless of the intensity of the stimulus; relative refractory period = the cell can fire an action potential only with a stimulus that is stronger than normal
176
What ion is primarily responsible for the fusion of neurotransmitter-containing vesicles with the nerve terminal membrane?
Calcium
177
What are the three main methods by which a neurotransmitter's action can be stopped?
Enzymatic degradation, reuptake, or diffusion
178
What parts of the nervous system are in the CNS? PNS?
CNS = brain and spinal cord; PNS = cranial and spinal nerves, sensory nerves
179
What do afferent/efferent neurons do?
Afferent (sensory) neurons bring signals from a sensor to the CNS; efferent (motor) neurons bring signals from the CNS to an effector
180
What functions are accomplished by the somatic/autonomic nervous system?
Somatic nervous system = voluntary action, especially moving muscles; autonomic nervous system = involuntary actions
181
What are the effects of the sympathetic/parasympathetic nervous system?
Sympathetic = "fight-or-flight", increased heart rate, bronchial dilation, redistribution of blood to locomotor muscles, dilation of pupils, slowing of digestive and urinary function; parasympathetic = "rest-and-digest", slowing heart rate and constricting the bronchi, redistributing blood to the gut, promoting exocrine secretions, constricting pupils, promoting peristalsis and urinary function
182
What is the pathway of neural impulses in a monosynaptic reflex? In a polysynaptic reflex?
Monosynaptic reflex = a sensory (afferent, presynaptic) neuron dires directly onto a motor (efferent, postsynaptic) neuron; polysynaptic reflex = sensory neuron may fire directly onto a motor neuron, but interneurons are used as well (the interneurons fire onto other motor neurons)
183
What is a true statement about action potentials?
Once an action potential is triggered, an impulse of a given magnitude and speed is produced
184
What is a difference between nerves and tracts?
Nerves may carry more than one type of information; tracts can only carry one type of information
185
A surgeon accidentally clips a dorsal root ganglion during a spinal surgery. What is a likely consequence of this error?
Loss of sensation at that level
186
When lipids leave the stomach, what stages of digestion have been accomplished? What enzymes are added to accomplish the next phase?
Physical digestion = in mouth and stomach, reducing particle size; chemical digestion = pancreatic lipase, colipase, cholesterol esterase, bile (in small intestine); absorption occurs in more distal portion of small intestine
187
True or False: All lipids enter the circulation through the lymphatic system.
False (small free fatty acids enter the circulation directly)
188
Describe the structure of a micelle.
Collections of lipids with their hydrophobic ends oriented toward the center and their charged ends oriented toward the aqueous environment (collect lipids within their hydrophobic centers)
189
A diabetic patient begins insulin injections for management of blood glucose levels. What is the expected impact on the patient's weight?
Increase in insulin levels -> increase lipid storage and decrease lipid mobilization from adipocytes -> weight gain
190
What is the ratio of free fatty acids to glycerol produced through lipid mobilization?
3:1
191
What is the primary method of transporting free fatty acids in the blood?
Free fatty acids remain in the blood, bonded to albumin and other carrier proteins
192
Order the lipoproteins from greatest percentage of protein to least percentage of protein. Which molecules are primarily involved in triaglycerol transport?
HDL (good cholesterol) > LDL > IDL > VLDL > chylomicrons
193
Lipoproteins are synthesized primarily by which two organs?
Intestine and liver
194
When physicians order a lipid panel to evaluate a patient, which value do they prefer to see over a minimum threshold rather than below a minimum?
HDL is considered "good" cholesterol because it picks up excess cholesterol from blood vessels for excretion (HDL would be checked for being over a minimum value)
195
Under what conditions is HMG-CoA reductase most active? In what cellular region does it exist?
HMG-CoA reductase is most active in the absence of cholesterol and when stimulated by insulin; cholesterol reduces the activity of HMG-CoA reductase, which is located in the smooth endoplasmic reticulum (HMG-COA = RATE LIMITING STEP IN CHOLESTEROL + KETONE SYNTHESIS)
196
What proteins are specific to the formation and transmission of cholesteryl esters, and what are their functions?
LCAT catalyzes the esterification of cholesterol to form cholesteryl esters; CETP promotes the transfer of cholesteryl esters from HDL to IDL, forming LDL
197
What are the five steps in the addition of acetyl-CoA to a growing fatty acid chain?
Attachment to acyl carrier protein, bond formation between molecules, reduction of a carbonyl group, dehydration, and reduction of a double bond
198
How does B-oxidation of unsaturated fatty acids differ from that of saturated fatty acids?
There is an additional isomerase and reductase for the B-oxidation of unsaturated fatty acids, which provide the stereochemistry necessary for further oxidation
199
True or False: Fatty acids are synthesized in the cytoplasm and modified by enzymes in the smooth endoplasmic reticulum.
TRUE
200
Why are fatty acids used to create ketone bodies instead of creating glucose?
Fatty acid degradation results in large amounts of acetyl-CoA which cannot enter the gluconeogenic pathway to produce glucose ; energy is packaged into ketone bodies for consumption by the brain and muscles
201
What conditions and tissues favor ketogenesis and ketolysis?
Ketogenesis: prolonged fast, occurs in the liver, increasing concentrations of acetyl-CoA; ketolysis: prolonged fast, low-energy state in muscle and brain, does not occur in the liver
202
True or False: Bodily proteins will commonly be broken down to provide acetyl-CoA for lipid synthesis.
False (proteins are more valuable to the cell than lipids)
203
Where does the bulk of protein digestion occur?
Small intestine
204
During protein processing, what is the eventual fate of each of the following components: carbon skeleton, amino group, side chains?
Carbon skeleton: transported to the liver for processing into glucose or ketone bodies; amino group: feed into urea cycle for excretion; basic side chains end up like amino group, acidic side chains end up like carbon skeleton
205
What are enzymes used for lipid digestion in the digestive tract?
Pancreatic lipase, cholesterol esterase, colipase (colipase required for optimal activity of pancreatic lipase)
206
What is the fate of long-chain fatty acids that are contained within molecules?
Transport into chylomicrons released into the lymphatic system
207
During fatty acid mobilization, which of the following occurs?
HSL is activated, free fatty acids are released
208
How do chylomicrons and VLDL differ?
Chylomicrons are synthesized in the intestine, VLDL are synthesized in the liver
209
What could result from an absence of apolipoproteins?
An inability to secrete lipid transport lipoproteins, an inability to endocytose lipoproteins, a decreased ability to remove excess cholesterol from blood vessels
210
Statin drugs inhibit HMG-CoA reductase. As such, they are likely prescribed for:
Hypercholesterolemia (high cholesterol)
211
Which fatty acid can be synthesized by humans?
16:0 (palmitic acid -> 16 carbons)
212
The majority of triacylglycerols stored in adipocytes originate from:
Synthesis in the liver
213
2,4-Dienoyl-CoA reductase is used in the oxidation of:
Polyunsaturated fatty acids
214
What is true regarding ketolysis?
Ketolysis generates acetyl-CoA (breakdown of ketone bodies to make acetyl-CoA for energy, occurs in muscle tissue/brain)
215
What is LEAST likely to result from protein degradation and processing by the liver?
Fatty acids (prolonged starvation state -> gluconeogenesis won't produce fatty acids)
216
Why can heat be used as a measure of internal energy in living systems?
Delta U = Q - W , W = 0 -> Delta U = Q
217
How does coupling with ATP hydrolysis alter the energetics of a reaction?
Yields about 30 kJ/mol of energy, can be harnessed to drive other reactions forward
218
Explain why ATP is an inefficient molecule for long-term energy storage
ATP is an intermediate energy-storage molecule and is not energetically dense
219
Name electron carriers and their relevant metabolic pathways in the cell.
NADH (glycolysis, fermentation, citric acid cycle, ETC); NADPH (PPP, lipid biosynthesis, bleach formation, oxidative stress, photosynthesis); CoQ: ETC; cytochromes: ETC ; glutathione: oxidative stress
220
Provide an example of disequilibrium that is maintained at the expense of cellular energy.
Sodium-potassium pump
221
What tissue is least able to change its fuel source in periods of prolonged starvation?
Cells that rely solely on anaerobic respiration
222
During which stage is there the greatest decrease in the circulating concentration of insulin?
Postabsorptive state
223
Describe insulin.
Promotes glucose uptake by adipose tissue in muscle, glucose utilization in muscle cells, and macromolecule storage
224
Describe glucagon.
Increases blood glucose levels by promoting glycogenolysis, gluconeogenesis, lipolysis, and ketogenesis
225
Describe cortisol.
Increases lipolysis and amino acid mobilization, while decreasing glucose uptake in certain tissues (increasing glucose levels) and enhancing the activity of other counterregulatory hormones
226
Describe catecholamines.
Increase glycogenolysis/gluconeogenesis (stop glycogen synthesis) in muscle and liver and lipolysis in adipose tissue
227
Describe thyroid hormones.
Increase basic metabolic rate and potentiate the activity of other hormones, produces calcitonin (thyroid hormones: T3 (3 iodines) and T4 (4 iodines))
228
What vital sign abnormalities might be expected in a patient with thyroid storm?
Hyperthermia, tachycardia, hypertension, tachypnea (high respiratory rate)
229
What is the preferred fuel for cells in the well-fed state?
Glucose (exception = cardiac muscle, which prefers fatty acids)
230
What are the major metabolic functions of the liver?
Maintaning a steady-state concentration of glucose in the blood through glucose uptake and storage, glycogenolysis, gluconeogenesis; participates in cholesterol and fat metabolism, urea cycle, bile synthesis, detoxification of foreign substances
231
How is the respiratory quotient expected to change when a person transitions from resting to brief exercise?
Will cause the respiratory quotient to approach 1 (RQ = CO2 produced / O2 consumed)
232
What is true about the hydrolysis of ATP?
The free energy of hydrolysis of ATP is nearly the same as for ADP
233
How do hormonal controls of glycogen metabolism differ from allosteric controls?
Hormonal control is systemic and covalent
234
What tissue is most dependent on insulin?
Resting skeletal muscle
235
In the absence of oxygen, which tissue would experience damage most rapidly?
Brain
236
A respiratory quotient approaching 0.7 indicates metabolism primarily of which macromolecule?
Lipids
237
What side effect would be anticipated for someone taking leptin to promote weight loss?
Drowsiness
238
How many times are ATP stores turned over per day?
1000
239
Which process is expected to begin earliest in a prolonged fast?
Enzyme phosphorylation and dephosphorylation
240
The toxic cyanide anion (CN-) binds to cytochrome c oxidase and prevents electron transfer. Dosing of BP-CML cells with cyanide would result in:
Reduced intracellular ATP and apoptosis or necrosis (would slow down ETC)
241
If oxygen consumption is reduced, what should happen to NADH levels?
NADH levels would increase (ETC would not be functioning properly, so NADH would not be oxidized to NAD+ and H+)
242
If a compound is already inhibiting the ETC, adding a compound that decouples the proton gradient across the inner mitochondrial membrane would:
Not have a strong effect on the cells
243
Why would hyperventilation lead to a decreased blood CO2 concentration?
The rate of CO2 exhalation exceeds the rate of CO2 production in the cells (main source of CO2 = production in krebs cycle)
244
In red blood cells, bicarbonate can be exchanged for chloride in the plasma. Why do red blood cells in venous circulation have a higher concentration of chloride ions?
Higher concentrations of CO2 in venous erythrocytes produce bicarbonate and drive the exchange of Cl- from the plasma into the cell
245
If blood pH goes down, it could be shown by:
Anaerobic respiration leading to lactic acid buildup, hypoventilation, and underproduction of bicarbonate
246
What are integrins?
Transmembrane receptors that modulate cell-to-extracellular matrix interactions
247
What are cadherins?
Transmembrane proteins which play a primary role in cell-to-cell adhesion
248
What is dynein?
A motor protein that moves cellular "cargo" along microtubule "train tracks"
249
What is a promoter?
Upstream DNA sequences in the eukaryotic genome that bind with transcription factors
250
What is an operator?
Structures in operons, which are involved in prokaryotic gene expression
251
What is the G-ratio?
The ratio of the diameter of the myelinated region surrounding the axon to the diameter of the axon itself (G-ratio = 1 if no myelination)
252
What would explain the failure of doxycycline to inhibit human protein synthesis?
Eukaryotic ribosomes lack a binding site for the drug
253
If a ribosome can bind aminoacyl-tRNA for binding to the A site of the 30s ribosome subunit even though the drug is not bound:
The drug is not able to stop protein synthesis
254
Increased protein solubility in aqueous solution will most likely result from:
More S, T, N, or Q residues on the outside of the protein
255
During rat embryogenesis, researchers noticed the development of a fluid-filled cavity in cells that had previously undergone morulation. That cavity was most likely a:
Blastocoel
256
During the isoelectric focusing procedure, cytokine Z migrated closer to the cathode than the control protein. This is most likely because Cytokine Z has a higher concentration of which amino acid?
Lysine (positively charged amino acid)
257
Which of the following changes would most likely be found in patients with mitochondrial myopathy?
Muscle aches due to lactic acid buildup
258
What makes an alcohol primary, secondary, or tertiary?
The number of carbons that surround the alcohol
259
Which of the following is most likely true of the 5'-UTR region?
It is transcribed, but is typically not translated or is only partially translated
260
What does a mature mRNA consist of?
A 5'-cap, the 5' UTR, coding regions, the 3' UTR, and a poly(A) tail
261
According to the passage, what total length of DNA is found in the average human cell before it is condensed for mitosis?
(6 x 10^9 bp)(0.3 x 10^-9 m/bp) = 1.8 m
262
Arrange the following in increasing order of compactness: nucleosome, heterochromatin, euchromatin, DNA helix.
DNA helix < euchromatin < heterochromatin < nucleosome
263
Defects in which of the following proteins would most likely lead to loss of structural integrity in skin epithelial cells?
Intermediate filaments (microtubules are also for structural integrity, but NOT in skin)
264
The frequency of the allele for colorblindness is 8%. Which of the following is the frequency of colorblind women and colorblind men in the population, respectively?
Frequency of gene = 0.08 -> odds of being homozygous = 0.0064 = 0.64%, since men only need a single copy of the gene, their odds would be 8%
265
What is the difference between transformation, transduction, and conjugation?
Transduction = DNA is transferred from one bacteria to another by a virus; transformation = genetic alteration of cell from direct uptake and incorporation of exogenous material; conjugation = transfer of genetic material, ordinarily in the form of a plasmid
266
It was proposed that nucleic acids were composed of a single tetramer of four nitrogenous bases linked by a circular, sugar-phosphate backbone. What apparent weakness exists in applying this model of nucleic acid structure to the experimenters' conclusion regarding the source of genetic information?
The model does not contain sufficient structural complexity to explain genetic variation
267
What would challenge the researchers' conclusions regarding the identity of the genetic material involved in the experiment?
Protein which happened not to pick up the 35S label entered the cell from the phage
268
What disease does angiogenesis play a role in?
Cancer
269
The researchers later used SDS-PAGE and size-exclusion chromatography to separate different mixtures containing both CP8 (a 76-kDa protein) and Zp_127 (a 40-kDa protein). CP8 would be expected to:
Travel a smaller distance during SDS-PAGE and elute more quickly during size-exclusion chromatography
270
Women over 35 years of age have an increased risk of nondisjunction due to errors in what phase of meiosis?
Anaphase II
271
Which of the following factors would be most likely to cause acetic acid to completely dissociate in aqueous solution?
Continuous removal of protons from the solution
272
How do Kd and the Hill coefficient relate to cooperativity/binding affinity?
Kd = lower the Kd, more binding affinity; a Hill coefficient around 1 means positive cooperativity
273
If further study of the samples was conducted to assess the extent of vascularization in each muscle type, which sample is likely to be the most vascularized?
Flight muscle of insects
274
The kidney's response to alcohol consumption is most similar to its response to:
Low blood osmolality and high blood pressure (alcohol decreases water reabsorption in the kidney)
275
Are either ethylene glycol or glycolic acid toxic?
Glycolic acid is
276
What gives rise to the mesoderm?
The musculoskeletal system, the circulatory system and the kidneys
277
What type of DNA-histone interactions promote transcription?
Loose interactions
278
Valproic acid dissociates in water to form its conjugate acid, valproate. Valproate is expected to associate most strongly with a protein rich in which of the following residues?
K (Lysine)
279
When does synapsis/chromosomal crossover take place in meiosis?
Proophase I
280
A fatty acid is composed of a carboxylic acid head and a tail end composed primarily of:
Hydrocarbon groups
281
Between ATP, NAD+, creatine phosphate, and acetyl-CoA, which one does not contain high-energy bonds?
NAD+ (low-energy state of NADH)
282
What is a scenario that demonstrates the second law of thermodynamics?
A catabolic process may be coupled with an anabolic reaction, yielding a net increase in entropy
283
A phosphotransferase enzyme with a cysteine residue in its active site acts on ATP to form an intermediate. What molecule acted as a leaving group in the first step of this interaction?
ADP
284
By coupling an unfavorable reaction to the hydrolysis of ATP:
The coupled reactions become exergonic overall
285
What species generated in the Krebs cycle has the greatest energetic yield?
NADH
286
A researcher is attempting to overexpress a gene in a positive inducible operon. The operon is currently not transcribed because the activator proteins are unable to bind the DNA. To increase the transcription of this operon, the researcher could add:
An inducer
287
What does methylation of a gene do?
It lowers its ability to undergo transcription
288
In a certain population of wild coyotes, brown fur (B) is dominant over spotted fur (b) and approximately 80% of a given breeding population has brown fur. Over the course of two decades, a genetic change occurs such that nearly the entire population expresses the spotted fur phenotype. In this population:
Spotted fur is the wild type
289
Unlike humans, birds use a ZW sex-determination system in which males have two Z chromosomes and females have one Z and one W chromosome. What is the most likely regulatory mechanism for the potential imbalance in gene expression between male and female birds?
Inactivation of one Z chromosome in males
290
In which of these stages do homologous chromosomes separate into distinct cells?
Anaphase of meiosis I
291
What is true about genetic drift?
It can lead to loss of alleles from the population, it can lead to alleles becoming fixed in a population, it is the result of random allele segregation from parents
292
A researcher tries to express the human gene for insulin, screened from the human genomic library, in a bacterial cell. The translated protein fails to fold into its functional native conformation. What could explain this misfolding?
The genes in the human genomic library contain introns, which cannot be excised by the bacterial cell
293
In the process used to create cDNA, the ssDNA produced by reverse transcriptase can be made into dsDNA through treatment with DNA polymerase I. In this case, no primer is required because:
The 3' end of the DNA strand often loops back onto itself, thereby providing a primer for the enzyme
294
Restriction enzymes interact with the intact DNA double helix. What are some explanations of why these proteins bind to the major groove?
The major groove offers more space for the enzymes to access the sides of the bases, the enzymes would be unable to tell the difference between an A-T and a T-A pair in the minor groove, and the enzymes cannot bind to phosphate groups in the DNA backbone in a sequence-specific way
295
Although PCR protocols almost exclusively employ heat to induce DNA denaturation, alternative denaturation methods are often used for Southern blotting. Which of these solutions would be LEAST effective when separating DNA strands to enable adherence to the blotting membrane?
A mild Mg2+ solution
296
EtBr is a standard laboratory reagent used to indiscriminately label DNA to use in an electrophoresis gel. The EtBr molecule is both charged and hydrophobic, which allows it to intercalate between stacked base pairs. When intercalated in this manner, the conjugation state of the molecule is altered such that it vividly fluoresces. Suppose that EtBr is introduced into a PCR solution and allowed to remain throughout multiple thermal cycles. Fluorescent intensity would most likely:
Fluctuate multiple times throughout the procedure
297
Much effort has been exerted to optimize the timing and temperature ranges of the PCR thermal cycle, thus maximizing desired DNA yield and minimizing error. Poor yield in a PCR reaction could most reasonably be attributed to which of the following phenomena?
Magnesium stabilizes DNA double helices
298
Following a properly conducted western blot, the researcher is unable to obtain any conjugation and the blot yields no signal for the protein of interest. Immunoprecipitation conducted on the sample using the same monoclonal antibody under neutral conditions returns a pure sample of the desired protein; however, results are less successful under mildly alkaline conditions. Which of these statements is a possible explanations for these results?
The protein of interest is a dimer, and the antibody binds at the junction between two monomers
299
One advantage of using human embryonic stem cells versus human adult stem cells is that:
Embryonic stem cells are pluripotent, while adult stem cells are multipotent
300
The diverse category of eukaryotic non-coding RNA includes:
microRNA, snoRNA, and tRNA, but not mRNA or hnRNA
301
Nucleic acids that can catalyze biological reactions include:
RNA only
302
The more unsaturated a fatty acid is:
The more unlikely it is to be a component of a lipid raft
303
Suppose the electrical potential of a certain membrane were determined entirely by the relative concentrations of potassium ions on either side. If the value of [K+] both inside and outside the cell were cubed, in comparison to before, the membrane potential:
Would increase by a factor of 3
304
What molecule does NOT require a channel, transporter, or vesicle to cross the plasma membrane?
Testosterone (steroid hormone)
305
What are some properties of DNA?
DNA carries the instructions necessary for all cellular functions, and DNA can be found in a supercoiled structure when it is not being actively transcribed or replicated
306
Eukaryotic DNA polymerase requires a free 3' -OH group, which is provided by a short RNA strand synthesized by primase enzymes. This -OH group is necessary because:
It binds to DNA polymerase, which otherwise cannot initiate synthesis
307
Suppose an organism contains an enzyme that can insert one random string of nucleotides into the coding portion of a gene. If this enzyme performs its function once on a particular gene, what is the probability that the resulting protein will be translated in the same frame as it would be if unmodified?
1/3
308
Which type of RNA is most active during post-transcriptional processing?
snRNA
309
What is true about DNA and RNA?
DNA contains a more stable sugar than RNA, RNA can catalyze biochemical reactions but DNA cannot
310
A drug that disrupts hydrogen bonding would most directly affect what level of protein structure?
Secondary (tertiary = HYDROPHOBIC interactions)
311
What is a part of translation that that is uniquely prokaryotic?
Translation requires multiple release factors (RFs) that trigger translation termination
312
How are heterochromatin and euchromatin different in regards to transcription?
Euchromation is associated with increased levels of transcription, while heterochromatin is related to the downregulation of transcription
313
What correctly describes the fluid mosaic model?
Describes the structure of the plasma membrane as a mosaic of components —including phospholipids, cholesterol, proteins, and carbohydrates—that gives the membrane a fluid character
314
What describes transmembrane proteins?
They act as receptors for hormones and initiate signal transduction pathways, they allow for transport of charged molecules across the cell membrane, they are responsible for the production of the majority of the ATP synthesized in eukaryotic cells
315
What does hypertonic mean?
Having a higher osmotic pressure than a certain fluid
316
Pinocytosis, sometimes called "cell drinking," involves the engulfment of extracellular fluid and any associated solutes by one or more vesicles. Pinocytosis is a form of:
Active transport and endocytosis
317
What does peroxisome do?
Breaks down lipids
318
A middle-aged man has a condition that impairs the synthesis of microtubule linking proteins. This disorder most likely impairs the function of:
Spermatoza (microtubule linking proteins) bind bundles of microtubules together, most notably observed in eukaryotic flagella
319
What type of cells have high rigidity and low tensile strength?
The brain
320
What describes gram-positive bacteria?
Thick cell wall, outer membrane absent
321
How would a bacteria sample show to be anaerobic?
Anaerobic = it does not collect towards the top
322
What is transduction?
A bacteriophage transfers genetic material from one bacterial cell to another during infection
323
The activity of a Class I transposon, also known as a retrotransposon, involves:
A conversion of DNA to RNA, RNA to DNA, and the production of an additional copy of the transposon (transposon = chromosomal segment that can undergo transcription)
324
What is a true statement about reverse transcriptase?
It is carried within the retroviral capsid and released into the cytosol following viral penetration
325
Why would common antibiotic resistance methods not apply to viruses?
Viruses are acellular
326
If a mutation caused similar but not identical results, what type of mutation is it?
Missense
327
In many patients, high-risk strains of HPV integrate themselves into the host's genome yet cause no symptoms for many years, making detection difficult. This period is most similar to which viral phenomenon?
The lysogenic phase
328
What is a part of neuromuscular junctions?
Acetylcholine
329
What type of primer does PCR use?
DNA primer
330
What are some functions performed by macrophages?
Antigen presentation, phagocytosis, and cytokine release
331
What does amphipathic mean?
Can be hydrophobic and hydrophilic
332
Lack of bile acids could lead to deficiency in which of the following?
Vitamin K (since it is fat-soluble)
333
What could be a treatment to reduce the amount of cholesterol in the body?
Prevent reabsorption of bile acids once excreted into the duodenum
334
Where in a eukaryotic cell would you be most likely to find the highest concentration of lipid peroxides?
Inner mitochondrial membrane (where redox reactions occur)
335
What would prevent the inverted genotype from causing an increasingly large skew in the sex ratio of a population?
Females with the inversion are much less healthy and demonstrate diminshed ability to forage and avoid predators
336
Between trisomy 21 and trisomy 14, which is likely to have the most deleterious effect and why?
Trisomy 14, because chromosome 14 has more genes and thus is more likely to contain a gene that is lethal at three equivalents
337
Why does polymerization occur much more rapidly at the (+) end of an actin polymer than at the (-) end?
The (+) ends of actin molecules display stronger intermolecular interactions than the (-) ends
338
A researcher compares two antibodies that recognize the same antigen, even though they are made by different animal species. How will these antibodies differ?
The antibodies will have different constant regions
339
In a particular biological system, 10 mM of substrate is present. If the initial velocity of the associated enzyme-catalyzed reaction is one-eighth of its Vmax, Km is equal to:
V0 = Vmax [S] / Km + [S] -> 1/8 = [S] / (Km + [S]) -> Km = 70 mM
340
The amino acid with the chemical formula C5H11NO2S:
Is not able to form disulfide bonds with other residues, because it does not possess a free thiol group
341
To be classified as an aromatic amino acid, a residue must:
Include at least one conjugated system, like tyrosine
342
Proteins fold in such a way as to maximize favorable interactions. If a particular protein is meant to function in a solution of oil, where would one expect a region rich in serine, threonine, and asparagine residues to be located in its tertiary structure?
In the protein's inner core
343
Tyrosine kinase inhibitors (TKI) are molecules that lodge in the active site of the tyrosine kinase enzyme. Glutamate (Glu) is one of the essential residues on the kinase that hydrogen bonds with the substrate. In this interaction:
The -COO- from the side chain interacts with the -NH on TKI
344
In glycolysis, what is the net yield of ATP per molecule of pyruvate produced?
1 ATP molecule
345
Lactose is a common disaccharide that can be digested by lactase into two monosaccharide units. What are the products of this catabolism, and can they enter directly into glycolysis?
One molecule of D-galactose and one molecule of D-glucose; only D-glucose can enter into glycolysis
346
What is the NADH to FADH2 ratio in the Krebs cycle?
3:1
347
Throughout the Krebs cycle and oxidative phosphorylation, how many molecules of ATP are formed per molecule of acetyl-CoA?
10
348
The human gluconeogenetic pathway cannot utilize:
Acetyl-CoA
349
What would be the expected effect on the pentose phosphate pathway during times of starvation?
Reduced activity, due to lower overall glucose concentrations in the body
350
An opiate overdose slows the respiratory drive, resulting in decreased gas exchange across the alveoli. This can damage tissues or cause death from:
Cell damage resulting from reduced ATP levels
351
A pharmaceutical compound targets and inhibits the carnitine shuttle used by cells. A human cell treated with this medication currently displays excess acetyl-CoA inside the mitochondria and insufficient cytosolic acetyl-CoA. What will be the most direct result of this circumstance?
Fatty acid synthesis will be inhibited
352
Which of these enzymes act upon a-1,4 linkages in polysaccharides?
Glycogen synthase, glycosyltransferase, glycogen phosphorylase
353
A congenital defect in the synthesis of the proteins cloudin and occludin is most likely to impact the function of:
Intestinal lining
354
A neuroscientist observes that treatment of temporal neurons with a certain toxin causes a depolarization of approximately 8 mV as compared to the resting value, but no action potential. He hypothesizes that this is caused by the opening of additional voltage-gated sodium channels. Is this explanation reasonable, and if not, why?
Yes, this explanation makes sense
355
What organ synthesizes the hormone ADH?
Hypothalamus
356
Compare steroid and peptide hormones.
Steroid = derived from cholesterol, small and nonpolar, travels the membrane without a channel; Peptide = large and relatively polar, unable to enter a cell through its plasma membrane, bind to extracellular receptors
357
Asthma is a potentially life-threatening condition characterized by the sustained contraction of bronchiolar smooth muscle, resulting in bronchoconstriction. What would most likely be effective in the treatment of asthma?
Terbutaline, a beta-receptor agonist often administered to prevent preterm labor
358
To prolong submersion time, some divers will hyperventilate immediately prior to a dive. This behavior is particularly dangerous and can result in drowning because:
Hyperventilation allows for the elimination of too much carbon dioxide, which can eliminate the urge to breathe
359
Which of the following conditions is/are most likely to cause a substantial decrease in tidal volume?
Late pregnancy and narcotic overdose
360
While the heart pumps blood to both the systemic and pulmonary circuits, coronary arteries supply blood to the heart tissue itself. A cardiothoracic surgeon isolates a sample of myocytes from the inner lining of one of these vessels. This sample most likely contains:
Smooth muscle
361
Increased blood viscosity is a known contributor to the development of chronic hypertension. Which of the following is likely to increase blood viscosity?
Sickle-cell anemia
362
Shortly after engulfing bacteria, macrophages undergo a "respiratory burst" characterized by substantial ATP production in matter of milliseconds. This metabolic activity is so intense that macrophages usually die after engulfing 40-50 bacteria. The purpose of the respiratory burst is most likely:
To provide energy for the rapid acidification of phagosomes via proton pumps
363
Cancer cells frequently exist in an immunologically privileged environment within the body. This is accomplished by production of high levels of cytokines, including transforming growth factor (TGF). Of the following, the cells that are most likely activated by TGF is:
Suppressor T cells
364
The 70-nucleotide hairpin structure of pre-miRNA is an example of secondary structure for nucleic acids. Which of the following strucutes would be similarly classified?
tRNA cloverleaf
365
What is the most likely reason that bacteria are not a reliable source of miRNA?
Most bacterial genomes contain no introns and are unable to produce RNA polymerase II
366
Who would be most likely to be a symptomatic carrier of an X-linked recessive disorder?
Males
367
A mutation in splicing factors is theorized to be the cause of the autosomal dominant form of retinitis pigmentosa, the progressive loss of retinal cells. What is the most likely reason this mutation occurs so rarely (1 in 7000) in live births?
Defects in general splicing machinery are generally incompatible with embryonic development
368
A portion of the LMNA mRNA transcript is 5′-AUGCCUAUCGUAACA-3′. What is the sequence of the template DNA from which this mRNA was copied?
5'-TGTTACGATAGGCAT-3'
369
Which type of fat is more flexible/fluid?
Unsaturated fats because of the double bonds
370
What is beta oxidation?
The process by which long chain hydrocarbons are oxidized to acetyl-CoA by enzymes in the mitochondria
371
Capilaries are composed of:
A single layer of endothelial cells
372
If compoound A exerts negative feedback on compound B:
There would be a low level of compound B when there is a high level of compound A
373
What can NEVER be a substrate for gluconeogenesis?
Acetyl-CoA
374
In eukaryotic cells, where is the highest concentration of phosphorus likely to be found?
Nucleus (DNA has more phosphorus than phospholipids)
375
What is cholecystokinin?
Acts in the small intestine upon the entry of food into the duodenum from the stomach, stimulates pancreatic acinar cells to release digestive enzymes, stimulates feelings of satiety, inhibits stomach emptying, lowers gastric acid secretion
376
Excessive levels of parathyroid hormone would stimulate activity of which of the following cells?
Parathyroid hormone increases blood calcium which is caused by an increase in osteoclasts
377
What pushes a cardiac myocyte above the threshold membrane potential level?
A neighboring cell's depolarization allowing some positive ions to enter through gap junctions
378
If Na+ channels close before the K+ channels open:
We would not observe a decrease in membrane potential
379
Why would the electrical signal need to travel more slowly through the AV node?
To allow the blood from the atria to enter the ventricles before their contraction
380
One way in which a ribosome can be seen to act as a ribozyme is that:
The ribosome can act as a scaffold that assists with the assembly of peptides from amino acids
381
The average liver contains close to 150 billion hepatocytes. According to the experiments discussed in the passage, if a patient has an acute MS infection lasting 24 hours, approximately how much oxygen will his or her liver consume in hour 25?
(40 x 10^-9 mol O2/min)(1/10^6 cells)(1.5 x 10^11 cells)(60 min/hour) = 3600 x 10^-4 mol O2 = 3.6 x 10^-1 mol O2 = 360 mmol O2
382
What is a cofactor?
A non-protein compound that is required for the activity of a protein
383
What is the most common variation that will result in the least change?
THE THIRD CODON
384
What does ELISA measure?
The amount of antigen in a sample
385
The cytochrome oxidase complex, encoded in part by COI, requires the transfer of electrons from how many molecules of cytochrome C in order to catalyze the formation of two molecules of water from molecular oxygen?
4 (4 cytochrome c -> 1 O2 -> 2 water)
386
Pancreatic alpha cells release:
Glucagon
387
Which phases of the pentose phosphate pathway should be activated to produce the greatest amount of nucleotides and NADPH, respectively?
Non-oxidative phase, oxidative phase
388
What are lacteals?
Structures in the intestines associated with absorbing fat into the lymphatic system
389
What is the epiglottis?
Part of the respiratory system, a flap of cartilage that covers the trachea to ensure that food properly remains in the digestive tract
390
How do the chemical modifications described in the passage differ from eukaryotic post-transcriptional modifications?
Post-transcriptional modifications are carried out entirely within the nucleus
391
Which phase of mitosis is likely to be interrupted if a cell has no microtubules?
Metaphase (spindle fibers are made up of microtubules)
392
How do gap junctions work in cardiac muscle?
Conducting nerve impulses with the appropriate timing needed for prompt, regular contractions
393
What are repressors?
Protein molecules that bind with DNA or RNA to prevent eventual translation of a protein
394
Chronic hyperglycemia directly leads to the presence of which of these molecules in the urine?
Glucose and ketone bodies
395
Uracil is usually found in:
tRNA and ribosomes (any structure made of RNA)
396
If something is an x-linked recessive order:
The female will need to carry the gene on both of her X chromosomes
397
What is true about the electron transport chain?
Electrons are passed from carriers with lower reduction potential to those with higher reduction potential, complex I is also a proton pump, and the electron carriers can transport a maximum of 2 electrons
398
Which location would have the highest number of glucagon receptors?
Liver
399
At physiological pH, what will be the principal interactions between Arg681 and Cys683?
Ion-dipole interactions between two chain B residues
400
Is SDS-PAGE page positively or negatively charged?
Negative
401
The production of the identified immunoglobulin would most directly involve which eukaryotic structure?
Ribosome
402
Compared to a neural cell, a gastrointestinal cell would likely spend:
Less time in G0
403
Cell differentiation is mediated primarily by:
Gene expression levels
404
What could explain a patient who presents with a blood pH of 7.0?
Anaerobic respiration leading to lactic acid buildup, hypoventilation, and underproduction of bacteria
405
A patient is administered a drug which makes the effects of the antagonist hormone of calcitonin. Which of the following is a likely direct effect of this drug?
Increased osteoclast activity
406
In comparison to unmyelinated neurons, myelination:
Increases the velocity of action potential transmission
407
Following puberty, the testes begin producing large amounts of testosterone. After production, the testosterone:
Diffuses into the circulatory system and is transported around the body while bound to a plasma protein
408
Which of the following patients will be expected to show the symptoms of mitochondrial myopathy?
A woman whose son has the disorder
409
2-chloropropane is treated with NaOH. Of the following, the most likely product to form would be an:
Secondary alcohol
410
A chemist looking to enhance parenteral nutrition attempts to create amino acids and sugars in the lab that are produced naturally in the body. He finds that his workups consistently produce racemic mixtures of the amino acids that the body normally synthesizes and uses in only a single enantiomeric form. The most likely reason for this distinction is that:
The enzymes the body uses are typically stereospecific and only produce one enantiomer
411
In the first trial of the PCR procedure, only one primer was added to the mixture. What was the likely outcome during this trial?
Only one strand of the DNA was linearly amplified
412
In humans, the quadriceps muscle is a skeletal leg muscle under voluntary control. As such, it contracts in response to signals from the motor cortex in the cerebrum. If such a muscle contracts involuntarily, that indicates:
The operation of a reflex arc
413
Diabetes mellitus is characterized by dysregulation of the hormone insulin. Which of the following statements about insulin is/are correct?
Insulin is produced by the beta cells of the pancreas and is a peptide hormone
414
A bacterium has a faulty lac operon in which there is a structural defect in the operator. In this bacterium:
There is a structural problem with a segment of DNA that binds a repressor
415
Unlike the cells from which human organs are composed, the cell of a unicellular organism such as algae:
Has a genome where nearly all material codes for protein
416
Which of the following segments of amino acids would be most likely to be found in the membrane-spanning domain of the sodium channel in a nerve axon?
LIV (hydrophobic amino acids)
417
GABA vs. glutamate?
GABA = inhibitory, glutamate = excitatory
418
If a protein is at a pH below its isoelectric point, which of the following is true?
The protein will have a net positive charge
419
If two defective alleles are required in order to develop a disorder:
The condition is recessive
420
PCR uses a:
DNA primer (coding strand -> same as mRNA -> complimentary to DNA in PCR -> complimentary to DNA primer in PCR)
421
Eukaryotic DNA polymerases:
Read the parental nucleotide template in the 3' -> 5' direction, adding nucleotides to the growing strand in the 5' -> 3' direction
422
Which of the following correctly identifies the order of development from fertilization to differentiation of the GI system?
Zygote → morula → blastula → endodermal cells → lining of archenteron → GI system
423
What is opsonization?
The process by which antibodies bind to and recognize antigens on the surface of the proteins
424
Which of the following could be a treatment to reduce the amount of cholesterol in the body?
Prevent reabsorption of bile acids once excreted into the duodenum
425
What does pancreatic lipase do?
Breaks down fats
426
Random selection would:
Decrease selection bias, influencing the accuracy
427
Where can lipid peroxides be found?
Where free-radical attacks on lipids occur, so where oxygen is participating in a redox reaction (inner mitochondrial membrane)
428
A lymphatic obstruction would cause:
A noticeable swelling of the tissue supplied by those lymph nodes
429
What type of cells/tissues would be directly affected by treatment with a drug that destroys capillaries?
Endothelial cells
430
Are collagen or elastin found in capillaries?
No
431
Can acetyl-CoA serve as a substrate for gluconeogenesis?
No
432
For what reason was 14CO2 production chosen to measure the rate of oxidation of labeled [1-14C] palmitate and TCA cycle flux?
14C contained in acetyl-CoA entering the TCA cycle may be incorporated into 14CO2.
433
A hiker out in the woods consumes a large amount of L. sativus seeds, which contain neurotoxic β-ODAP acid. 12 hours later, the hiker is having difficulty maintaining balance and opening her water bottle. What region of the brain is likely being attacked by β-ODAP?
Cerebellum
434
If something is sufficient to cause rapid cell prolieration:
The protein could serve as a transcription factor, tyrosine kinase, or signal transducer
435
Why does melanoma have a high rate of metastasis?
Proximity of melanocytes to blood vessels
436
Which of the following most likely pushes a cardiac myocyte above the threshold membrane potential level?
A neighboring cell's depolarization allowing some positive ions to enter through gap junctions
437
If the allele frequency q is found, what could be estimated using a population survey?
q^2
438
How many moles of ribulose could you create using the 30 moles of glucose 6-phosphate?
30
439
Which of the following does the complementary nature of the DNA sense strand and antisense strand encompass?
Every nucleotide base on the sense strand has a complementary base on the antisense strand
440
Why does RNA electrophoresis not require SDS?
RNA molecules already have a net negative charge proportional to the number of nucleotides
441
What are endonucleases?
Highly specific enzymes that recognize and hydrolyze phosphodiester linkages at unique palindromic sequences in DNA
442
Patients entering the ICU with acute liver failure often also display dramatically lowered plasma glucose concentrations. Which of the conditions below could promote the same effect in individuals without liver damage?
Understimulation of pancreatic alpha cells
443
Which cytoskeletal component forms the majority of the outer layer of skin?
Intermediate filaments
444
What is epinephrine?
Activates a G-protein coupled signal transduction pathway that activates glycogen phosphorylase (involved in glycogen degradation)
445
What in insulin?
A peptide hormone secreted by beta cells in pancreas, increases glucose uptake by liver and muscles, increases the rate of anabolic processes
446
What is gastrin?
A peptide hormones that stimulates secretion of HCl by the parietal cells of the stomach
447
What is somatostatin?
A peptide hormone secreted by delta cell of the pancreas, inhibits both insulin and glucagon and its release is triggered by high glucose and amino acid levels
448
Carbonic anhydrase 1 is a metalloenzyme that contains a tightly-coordinated zinc ion in its active site. Which of the following is expected to result from the complete inhibition of this enzyme?
A buildup of carbon dioxide in body tissues
449
In a remote hospital in Asia, a patient is suspected to have dengue fever, a life-threatening disease that causes increased vascular permeability. As a result, her physician can expect to find:
Generalized edema, increased renin levels, and decreased blood pressure (therefore increased heart rate)
450
Hepatic scarring that develops as a result of cirrhosis can lead to progressive loss of liver function. All of the following processes may be impaired due to cirrhosis:
Bilirubin excretion, blood clotting, and cholesterol production
451
What contributes to ring stability?
Torsional strain, caused by electron clouds of the molecule's substituents getting too near one another, non-bonded strain, caused by substituents on non-adjacent ring atoms being brought in close proximity, and angle strain, caused by bonding electrons of ring atoms being brought closer
452
Blood type in humans is a classic example of codominant inheritance. An AB+ male has a child with an O+ female. What is the likelihood that their first child will be able to receive a blood transfusion from a B- donor?
0.5
453
What are some differences between the genetic material in a parasitic bacterium and that of its eukaryotic hosts:
Presence of introns, size, number of origins of replication
454
Higher electronegativity:
Lowers polarity
455
The enhanced acidity of TFE when compared to ethanol is principally due to what factor?
Greater inductive withdrawal of electron density from the oxygen-hydrogen bond in TFE
456
What mechanism of gene transfer is most likely to be responsible for the transfer of genes from bacteria to a eukaryotic host?
Nuclear-phage recombination (conjugation and transformation are means of horizontal gene transfer among prokaryotes, transposable elements = moving genes around in the eukaryotic genome)
457
What is fibrinogen?
A soluble glycoprotein that is converted by thrombin into fibrin, which cross-links aggregated platelets during secondary hemostasis
458
What is an immunoglobulin?
An antibody produced by the immune system to bind to and neutralize antigens
459
In order for immersion of a neuron into a KCl solution to induce depolarization, what must be true of the relative ion permeability of the neuronal membrane?
It is high for K+ and low for Cl-
460
Oxidative breakdown can take place in:
Mitochondria and peroxisomes
461
What are some non-coding RNAs?
snRNA (associated with specific proteins), snoRNA (subset of snRNA, play a role in RNA biogenesis and modifications of rRNA and tRNAs), tRNA (does not get translated into a protein)
462
What are the basic amino acids?
Lysine, Arginine, and Histidine
463
Vitamin C acts as:
A cofactor in collagen synthesis
464
Vitamin A:
A
465
Vitamin B1:
Deficiency can lead to Korsakoff's syndrome
466
Vitamin D:
A group of fat-soluble steroid hormones responsible for enhancing intestinal absorption of calcium and phosphate
467
What are some exocrine glands?
Liver, pancreas, salivary gland
468
Injuries to cartilaginous tissue, such as torn and stretched ligaments, can often take quite some time to heal. Which statement best explains why injuries to this type of connective tissue heal so slowly?
Cartilage relies on diffusive rather than direct vascular delivery of nutrients, and repairing cells therefore have a hard time sustaining increased activity
469
Progressive multifocal leukoencephalopathy (PML) is a viral disease that causes inflammation of white matter in the brain and demyelination of the neurons. Symptoms include clumsiness, visual and speech abnormalities, and, occasionally, personality changes. From this information, PML most likely triggers the death of:
Oligodendrocytes
470
The parasympathetic nervous system promotes vasodilation in which of the following areas?
Small intestine and stomach
471
What are some functions of peripheral glia?
Insulation and protection of electrically active cells, clearance of cellular debris via phagocytosis, and secretion of small, soluble signaling molecules
472
Latrotoxin (LTX), a large globular protein produced by Latrodectus spiders, acts to perforate the presynaptic membrane at the axon terminal. The resulting channel is large enough to permit the free influx of calcium, as well as the passage of water and other small molecules. A Latrodectus bite would most likely result in:
Swelling of the axon terminal, fusion of docked vesicles with the plasma membrane, and widespread release of acetylcholine within the PNS
473
Under the conditions given, which of the following neurons is most likely to fire an action potential?
An unmyelinated neuron that receives multiple EPSPs that summate temporally
474
Tetrodoxin (TTX), a toxin found in pufferfish and other marine species, binds to and inhibits transmission through Na+ voltage-gated channels in neurons. An individual has spent the past six months consuming a small, daily dose of TTX to calm his restless legs. If this individual were to suddenly cease this medication, what neurological response is most likely?
His neurons will be unusually sensitive, since he had become accustomed to a lower amount of sodium influx, which is integral for the initial depolarization phase of the action potential
475
What hormones does the anterior pituitary produce?
PEPTIDES (FSH, LH, ACTH, TSH, prolactin, and GH)
476
An elevated ACTH and cortisone would be indicative of a tumor in what area?
Anterior pituitary
477
Which organ synthesizes steroid hormones?
Adrenal cortex
478
Administration of S. aureus-specific antibiotics to patients in shock is meant to:
Decrease the translation of SEB
479
Which of the following symptoms would be expected in a patient suffering from superantigen activation of T cells?
Increased tyrosine kinase activity, tissue hypoxia, and hypotension
480
Which of the following components, in addition to phospholipids, are likely to be found in whole or in part on the cytoplasmic face of a human plasma membrane?
Transmembrane protein and phospholipase A2
481
Skeletal muscle is especially rich in phospholipids, of which 10-20% are arachidonic acid. Which of the following changes would lead to a decrease in the fluidity of the sarcolemma?
Converting some of the arachidonic acid present into its all-trans unsaturated geometric isomer
482
What is the equation to look at osmotic pressure?
pi = iMRT (osmotic pressure = van't Hoff factor * molarity * gas constant * temp)
483
Cas9 is an endonuclease. An endonuclease acts to:
Cleave nucleic acid within a DNA molecule
484
What is a reason drug researchers would not include a negative control group in an experiment testing a new antibiotic?
It is unethical to withhold medical treatment when doing so poses a risk to the patient
485
Fertility researchers noticed that some metaphase II-arrested oocytes contain an abnormal chromosome number. Nondisjunction involving which of the following would be likely to create this abnormality?
Homologous chromosomes (sister chromatids separate on Anaphase II)
486
Endosymbiosis occurs when:
One organism lives inside another one
487
What is the Edman degradation?
A technique used to sequence peptides by progressively removing amino acids
488
What is X-ray crystallography?
Allows us to infer the 3D (secondary and tertiary) structure of the protein, but not its primary structure
489
What are the different types of Ig antibodies?
IgA = mucosal areas; IgG = most of the body's immune response; IgE = allergies, IgM = early immune response
490
A multicolored calico cat was cloned, and it was found that each of the cloned offspring showed unique coloring patterns. Which chromosome is the gene responsible for fur color in calico cats most likely to be on?
X
491
A geneticist is attempting to determine whether a recessive mutation is X-linked or autosomal. What information would be the most useful for her to gather?
Whether significantly more males than females show the effects of the mutation
492
What is used to analyze gene expression?
RNA sequencing
493
What is a polymorphism?
If a gene exists as more than one allele within the population
494
What is adaptive radiation?
A process by which organisms diversify rapidly into multiple new forms
495
Which of the following are responses to insulin production?
Activation of glycogen synthase and deactivation of glycogen phosphorylase
496
In a normally functioning myocyte, which of these molecules is expected to have the most positive reduction potential?
Oxygen (the final electron acceptor of the ETC)
497
A man is admitted to the hospital with abnormally high cortisol levels. Through multiple tests, it was discovered that the problem originated from a hormone-secreting tumor in his anterior pituitary. Other than elevated cortisol, what would you expect to find regarding this patient's hormone levels?
High adrenocorticotropic hormone and low corticotropin-releasing hormone
498
In individuals with diabetes, acute hypoglycemia can occur due to excess administration of insulin or other anti-diabetes medication under fasting conditions. In a patient with diabetes taking an α-glucosidase inhibitor, the best response to acute hypoglycemia would be to consume:
Fructose (monosaccharide)
499
What occurs in type 2 diabetes?
Impaired secretion of insulin by pancreatic beta cells and insulin resistance
500
Which process of carbohydrate metabolism does CZ extract interfere with?
Digestion (glucosidase is not involved in glycolysis, gluconeogenesis, and glycogen breakdown)
501
Why is increased urination an early sign of type II diabetes onset?
Excess glucose cannot be entirely reabsorbed by the kidneys; as a result, the urine is hypertonic, so it tends to increase in volume
502
Untreated type I diabetes and unmanaged type II diabetes lead to increased risk of stroke or heart attack. Why?
Endothelial cells in the blood vessel lining take in an excess of glucose, which causes them to overexpress surface glycoproteins, in turn weakening the basement membrane
503
With unmanaged diabetes, weight loss can begin to occur, even if there is no change in eating habits and less exercise than usual. This can be attributed to:
Fat being broken down as glucose leaves in the urine
504
While observing chromosomal crossover in a cell undergoing meiosis, students were most likely to have also observed what concurrent event?
Spindle formation
505
If MMR recruitment following HR-mediated repair occurs as proposed in the passage, chemical modification of cytosine to yield thymine most likely involves:
Removal of an amino group
506
Absent any mutagenic effects, HR-mediated repair is likely to have the greatest accuracy when the exchange of identical genetic information occurs between which molecules?
Sister chromatids during G2
507
What hormone causes stimulation of adipocytes (fat cells)?
Insulin
508
Stabilization of a conjugate base would cause:
Increased acidity
509
If something is omitted from the final mRNA sequence during pre-mRNA processing:
The deletions would probably contain splice acceptor sites
510
What is a clathrin?
A protein that plays a major role in formation of coated vesicles, important in endocytosis
511
What is a chaperone?
A protein that facilitates proper protein folding and inhibits the formation of nonfunctional protein aggregates
512
How do transmembrane proteins enter the endomembrane system?
By docking at the rough ER, which is facilitated using a signal sequence
513
What are nuclear localization signals used for?
To permit proteins to enter the nucleus
514
What is the total number of fused rings present in a steroid?
4
515
When concentrated urine is being produced, in which of the following regions of the kidney will the glomerular filtrate reach its highest concentration?
Medullary portion of the collecting duct
516
What measures the activity of Na+ K+ ATPase?
The rate of ATP hydrolysis, ADP production, and change in ion concentration within the liposome
517
What do transcription factors do?
Bind DNA and subsequently recruit RNA polymerase
518
If a molecule is planar and hydrophobic enough:
It can pass through the membrane using simple diffusion (small uncharged or hydrophobic molecules like lipids can pass)
519
What can receptor-mediated endocytosis be used for?
Metabolites, hormones, proteins, viruses
520
What are types of active transport?
Sodium potassium pump, endocytosis, exocytosis
521
What is a lipid raft?
A cholesterol rich domain
522
Colchicine is a drug that prevents the formation of microtubules. Which of the following mitotic processes would NOT occur after exposure to this drug?
Movement of the chromosomes toward opposite poles of the cell during anaphase
523
How do enzymes alter the rate of chemical reactions?
Co-localizing substrates, altering local pH, and altering substrate shape
524
What are enzymes?
Catalysts
525
What does it mean if the ornithine decarboxylase assay is highly specific?
It can distinguish ornithine decarboxylase activity from the many other enzymatic reactions in a cell
526
The process of culturing bacteria often involves inoculation of cells on a noncellular, agar-based medium. Such a methodology would NOT result in growth of animal viruses because animal viruses:
Are obligate parasites
527
In a phosphodiester bond:
The 5' end bears a phosphate group, and the 3' end bears a hydroxyl group
528
If cells of the adrenal cortex are destroyed:
ACTH secretion would be higher to attempt to stimulate the adrenal cortex
529
During the production of insulin, the translated polypeptide is cleaved into the mature form and secreted from the cell. The cleavage most likely takes place in which of the following locations?
The endomembrane system
530
1500 bases is equal to:
500 amino acids
531
What is connexin?
A gap junction protein
532
What is fibronectin?
A bridging protein which itself connects to collagen
533
What is occludin?
Comprises tight cell-cell junctions
534
Where does protein translation primarily occur?
The endoplasmic reticulum, which are then transported to the Golgi apparatus for post-translational modification, processing, and packaging for proper localization
535
What are some differences between Eukarya, Archaea, and Bacteria?
Eukarya = animals, plants, fungi, and protists; archaea = methanogens, halophiles, thermophiles; bacteria = micrococcus, staphylococcus, bacillus, pseudomonas
536
What would repeated usage of a mouse antibody result in a human?
Production of human anti-mouse antibodies
537
How many electrons can ubiquinone/cytochrome C carry?
Ubiquinone = 2, cytochrome c = 1
538
Yeast cells can grow under either aerobic or anaerobic conditions. If the same concentration of glucose were used to grow two different yeast colonies, would the growth rate be faster under aerobic or anaerobic conditions?
Aerobic, because a much greater amount of ATP would be produced to provide energy for reproduction
539
Where is GADPH expressed?
In euchromatin
540
When fewer visual pigment molecules are available to absorb light (for example, when a person has a color weakness), which of the following nervous system responses occurs?
Fewer signals of the weakly perceived color are sent to the brain
541
What is the difference between white and brown adipose tissue?
Mitochondria
542
Administration of a carbonic anhydrase inhibitor to the RBCs would most likely cause an increase in the concentration of:
CO2 in the tissues
543
Lung capillaries are so narrow that RBCs must pass through them in single file. This feature aids respiration by:
Giving maximum exposure of each RBC to diffusing gases
544
The endosome differentiates into:
Lysosome
545
What is the difference between an endonuclease and an exonuclease?
Endonuclease = cleave phosphodiester bonds that are present within the polynucleotide chain; exonuclease = cleave phosphodiester bonds on the 3' or 5' end
546
What is a ribonuclease?
Catalyzes the breakdown of RNA
547
The absorbance of a protein solution is 3.37. Is the concentration of the solution is known to be 4 M and the path length is 1 cm, which value best approximates the extinction coefficient?
Beer Lambert's Law -> A = eCl -> e = 0.08
548
A particular protein largely lacks both secondary and tertiary structure. Which factor, if any, is mainly responsible for the resting state of this protein?
Entropy
549
At the (-) end of a microtubule, depolymerization is prevented by:
Anchoring of that end to an MTOC
550
If two antibodies bind to the same antigen:
They have the same variable region
551
Dyneins, motor proteins that are associated with microtubules, play a vital role in the transport of cellular components. How can the intracellular movement of dyneins be described?
Dyneins travel towards the center of the cell, move towards the minus end of their associated microtubules, and are involved in retrograde transport
552
In a Cartesian coordinate system:
A typical rate vs. pH curve is parabolic in shape
553
What enzyme converts glucose to glucose-6-phosphate?
Hexokinase
554
What enzyme converts glucose-6-phosphate to fructose-6-phosphate?
Phosphoglucose isomerase
555
What enzyme converts fructose-6-phosphate to fructose-1,6-bisphosphate?
Phosphofructokinase
556
What enzyme converts fructose-1,6-bisphosphate to glyceraldehyde-3-phosphate?
Aldolase
557
What enzyme converts glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate?
Glyceraldehyde-3-phosphate dehydrogenase
558
What enzyme converts 1,3-bisphosphoglycerate to 3-phosphoglycerate?
Phosphoglycerate kinase
559
What enzyme converts 3-phosphoglycerate to 2-phosphoglycerate?
Mutase
560
What enzyme converts 2-phosphoglycerate to phosphoenolpyruvate?
Enolase
561
What enzyme converts phosphoenolpyruvate to pyruvate?
Pyruvate kinase
562
Where is chymotrypsin located?
Small intestine
563
What are coenzymes?
A subset of cofactors that tend to bind loosely to their associated enzymes, known for transferring functional groups between species (NAD+)
564
What is the Michaelis-Menten equation?
V0 = Vmax [S] / Km + [S]
565
What is a synonym for zymogen?
Proenzyme
566
If an enzyme participates in cooperative binding:
It will display a sigmoidal kinetic curve
567
What should a restriction enzyme cleave if they want to excise the promoter region?
The promoter and the gene region
568
If the angle between two complementary bases is termed the propeller angle, a base pair with a large propeller angle will:
Reduce the overall melting temperature of the DNA duplex due to reduced hydrophobic contact
569
What is immunohistochemistry used for?
Providing a detailed and visual report on the protein expression within a tissue
570
In SDS-PAGE, if a protein has a higher pI:
It would have more charged residues
571
How can a scientist running an SDS-PAGE procedure assure that the difference in running distance on the gel is due to the length of the peptide and not its shape?
Detergent is added to the running buffer (detergent, like soap, has a hydrophobic and hydrophilic ends, destroys hydrogen bonds)
572
What are some necessary reagants/molecules for a Western blot?
SDS, reducing agent, detection antibody
573
A protein from the urine of a chronically ill patient was isolated and run on an SDS-PAGE gel. The result displayed on the gel was a long smear instead of a crisp band. These results can most likely be attributed to the fact that:
The protein was partially degraded
574
What is a specific type of affinity chromatography?
Immunoaffinity chromatography, which utilizes antibodies (or immunoglobulins) within the column
575
If leucine and valine are run through the same ion-exchange chromatograph:
It would not be possible to determine which peak corresponds to which amino acid
576
What are a few statements that describe tryptophan at physiological pH?
It has no net electrical charge, and it is neither acidic nor basic
577
When looking at pKa values of an amino acid:
The value with the higher pKa is usually the amino group
578
Two cysteine residues undergo a reaction to form a disulfide bond. Which of these reactions can be coupled to this process?
NAD+ -> NADH (disulfide bond formation = oxidation, can be coupled with a reduction)
579
Given a polypeptide chain with a net positive charge, in which direction will it migrate during electrophoresis at a pH of 8.0?
It will migrate towards the negative pole
580
Acidic and basic amino acids can be freely found in the bloodstream. How are these molecules involved in buffering the plasma at physiological pH?
Under low-pH conditions, acidic amino acids can decrease H+ concentration
581
Hydrogen bonding occurs between:
A hydrogen atom (that is connnected to N, O, or F) and an electrophilic center
582
According to Le Chatelier's principle, which glycolytic disturbances would force the metabolic system to reestablish equilibrium?
Increased concentrations of glucose, decreased concentrations of pyruvate, and decreased availability of ATP (conc. of enzymes does not affect)
583
What makes a reaction easily reversible?
Delta G = 0
584
Between ATP, NAD+, creatine phosphate, and acetyl-CoA, which one has a low-energy bond?
NAD+
585
What is the second law of thermodynamics?
A spontaneous reaction or cyclic process must yield a net entropy increase increase (entropy should be continually rising)
586
By coupling an unfavorable reaction to the hydrolysis of ATP:
The coupled reactions become exergonic overall
587
A deficiency in which of the following biological molecules will result in a halt in glycolysis?
ADP
588
What is sucrose made of?
Glucose and fructose (alpha-1 on the glucose and beta-2 on the fructose)
589
A researcher obtains pure glyceraldehyde 3-phosphate and uses it to mimic glycolysis and gluconeogenesis in vitro. If the researcher uses 6 moles of G3P, what is the maximum number of moles of pyruvate or moles of glucose that can be generated?
6 moles of pyruvate or 3 moles of glucose
590
It has been noted that certain cancers are linked with high rates of aerobic metabolism. A researcher desires to track the metabolic rate in a series of cell cultures. This researcher should monitor the formation of which product?
CO2 (a waste product of aerobic respiration)
591
During the Krebs cycle:
Each unit of acetyl-CoA forms three molecules of NADH and one molecule of FADH2 (NADH:FADH2 ratio = 3:1)
592
What is decarboxylation?
Releasing a carboxyl group
593
Throughout both the Krebs cycle and oxidative phosphorylation, how many molecules of ATP are formed per molecule of acetyl-CoA?
10 -> acetyl-Coa = 3 NADH, 1 FADH2, and 1 GTP = 3(2.5) + 1.5 + 1 = 10
594
In the electron transport chain:
Protons flow from the extracellular matrix to the intermembrane space
595
Which complex, I or II, is focused on NADH/FADH2?
Complex I = NADH, Complex II = FADH2
596
What molecule cannot be used in gluconeogenesis?
Acetyl-CoA
597
Where does gluconeogenesis take place?
Mostly liver, also the kidneys
598
Why is the S phase of the cell cycle reasonable to expect the highest activity of the pentose phosphate pathway?
The pentose phosphate pathway produces ribose-5-phosphate, which plays a role in nucleic acid synthesis
599
What are the products of the pentose phosphate pathway linked to?
Glycolysis (glyceraldehyde 3-phosphate), fatty acid synthesis and glutathione reduction (NADPH)
600
What would the expected effect on the pentose phosphate pathway during times of starvation?
Reduced activity, due to lower overall glucose concentrations in the body
601
An opiate overdose slows the respiratory drive, resulting in decreased gas exchange across the alveoli. This can damage tissues or cause death from:
Cell damage resulting from reduced ATP levels
602
BDNF is a plasma-soluble protein secreted after being manufactured in the endoplasmic reticulum. BDNF most likely:
Has its effect through binding receptors on the external leaf of the plasma membrane
603
Since insulin causes glucose uptake:
It's goal is to reduce blood glucose levels
604
A way to remember endonucleases vs exonucleases:
WHERE THEY CLEAVE NUCLEOTIDES (ends versus within)
605
Given the role of the reaction in cellular respiration, what is the most likely Eº value for the reduction of oxygen to water?
Positive voltage -> oxygen has to be more readily reduced than anything else in the ETC
606
Localized radiation therapy of the thyroid will most likely affect another endocrine gland that has which of the following characteristics?
Hyperactivity of the gland can cause osteoporosis
607
Can thyroid hormone and other tyrosine-based hormones passively transport through the cell membrane?
NO
608
In what order do electrons move through the ETC?
From carriers with lower reduction potential to carriers with higher reduction potential
609
If there is insulin uptaking glucose:
THERE IS NO NEED FOR GLUCONEOGENESIS
610
What are aquaporins?
Protein channels that induce water molecules to flow out of the cells and decrease their volume
611
What does endocytosis cause?
Uptake of material, not evacuation of material
612
What is the purpose of an adjuvant?
To enhance immune response against a pathogen
613
What are histones/centromeres made of?
Histones = arms of chromosomes, made of euchromatin; centromeres = center of chromosome, made of heterochromatin
614
For an x-linked recessive disorder:
Usually only males can get it from their mothers
615
ATP/GTP/etc belong to which class of biological molecules?
Nucleotides (base, sugar, phosphate group) - nucleosides have no phosphate
616
DCCD is a chemical that blocks the proton pore of ATP synthase. If treated with DCCD, which of the following is most likely to decrease in the actively respiring mitochondria of adult rat cardiac cells?
Oxygen consumption
617
Before your luteal phase (ovulation), you have your:
Follicular phase (menstruation/proliferative)
618
Between the veins, the Loop of Henle, the lungs, and bone marrow, where is the sodium pump the most active?
Loop of Henle
619
Action potentials result in an increased permeability to:
Sodium
620
How many molecules of ATP does glycolysis produce?
2 molecules of ATP per glucose
621
H. pylori infection may cause increased proliferation of mucosal cells in the stomach. This may lead to gastric cancer if:
Genetic mutations occur in proliferating somatic cells (mucosal cells in the stomach = somatic cells)
622
Hyperglycemia promotes cellular dehydration because:
Glucose molecules raise the osmotic pressure of the extracellular space (minimum pressure to prevent inward flow of solution)
623
What is a part of extracellular fluid?
Blood plasma and lymph
624
The lipases catalyze the hydrolysis of fats and other carboxylic acid esters. The lipases illustrate the fact that:
Some enzymes interact with several different substrate molecules that have similar chemical linkages
625
Inflation of the lungs in mammals is accomplished by:
Negative pressure pumping action (keeps airways of the lungs open)
626
An extra S phase would be triggered by the presence of:
Low concentrations of DNA in the macronucleus
627
Antisense drugs prevent:
RNA translation
628
To be an effective therapy, an antisense gene that is incorporated into a genome that contains the target gene must be:
Regulated in a similar manner as the target gene
629
When RNA molecules hybridize:
The antisense molecule would line up in an antiparallel fashion with the sense molecule
630
An effective and efficient method for the delivery of an antisense gene could be:
infection of an embryo by a virus modified to carry the gene (antisense gene delivery = hybridize with the sense mRNA)
631
If oligonucleotides such as mRNA were not degraded rapidly by intracellular agents, which of the following processes would be most affected?
The coordination of cell differentiation during development
632
The prolonged increase in heart and breathing rates during the snow skiing trip was probably a result of:
Hypoxia caused by insufficient blood hemoglobin concentration to supply oxygen for exercise at the low oxygen pressure found at high altitudes
633
What is myoglobin?
The substance that holds oxygen in the muscles and organs
634
Control of heart rate, muscle coordination, and appetite is maintained by the:
Brain stem, cerebellum, and hypothalamus, respectively
635
Sarah noted that her skin blood vessels were usually constricted to conserve body heat in the cold environment of the mountains. However, her skin blood vessels would occasionally dilate for short periods of time. What would be the most probable physiological purpose for this periodic vasodilation?
Maintain sufficient oxygenation of cells
636
What characteristic clearly marks fungi as eukaryotes?
Mitochondria
637
In mammals, which of the following events occurs during mitosis but does NOT occur during meiosis I?
The splitting of centromeres (splitting of centromeres does not occur until anaphase II)
638
Inbreeding can reduce the fitness of a population in the short term because it causes an increase in the:
Incidence of expression of deleterious recessive traits
639
How would a lower-than-normal blood pressure effect the rate of plasma clearance?
A decrease, because the decreased rate of urine output will allow more reabsorption by the kidney
640
The two primary factors that normally determine the level of blood pressure are:
The cardiac output and the resistance to blood flow
641
Increased vasoconstriction has an important role in which of the following situations?
Maintaining blood pressure during a hemorrhage
642
Accumulation of DDT in the testes may cause reduced fertility in males because the uncoupling of oxidative metabolism from ATP production may reduce:
Sperm motility
643
A damage of what structure causes a mutation?
Chromosome
644
The enzyme pepsin, which catalyzes the hydrolysis of proteins in the stomach, has a pH optimum of 1.5. Under conditions of excess stomach acidity, pepsin catalysis occurs very slowly. The most likely reason for this is that below a pH of 1.0:
The three-dimensional structure of pepsin is changed
645
An intravenous infusion causes a sharp rise in the serum level of albumin (the major osmoregulatory protein in the blood). This will most likely cause an:
Influx of tissue fluid to the bloodstream (osmoregulation = will change the concentration of bloodstream, tissue fluid has to come in to balance it out again)
646
Most bacterial cells and human cells are alike in:
The ability to produce ATP via ATP synthase
647
Why do calcium supplements often include vitamin D?
The activated form of vitamin D stimulates the absorption of calcium into the blood
648
A low level of calcium in the plasma will trigger an increase of:
Osteoclast activity and parathyroid hormone
649
What would be the result of complete removal of the parathyroid glands?
Severe neural and muscular problems due to deficiency of calcium in the plasma
650
If Anolis lizards have X-Y chromosomal sex determination, the locus of a gene for the UV reflectance pigment:
Could be on a sex chromosome or on an autosome
651
Dewlaps that reflect UV light would evolve by natural selection only if:
Individuals with UV-reflective dewlaps produced more offspring than did individuals without them
652
Aldosterone stimulates Na+ reabsorption by the kidneys. What changes in blood volume and pressure would be expected as a result of aldosterone deficiency?
Decreased volume and decreased pressure
653
The sequence of events in the human menstrual cycle involves close interaction among which organs?
Hypothalamus-thyroid-ovary
654
Which of the following changes would NOT interfere with the repeated transmission of an impulse at the vertebrate neuromuscular junction?
An increase in acetylcholine receptor sites on the motor end plate
655
Which statement below most accurately describes the roles of the proteins actin and myosin during muscular contraction?
Bridges between actin and myosin form, break, and re-form, leading to a shortening of muscle sarcomeres
656
A drug that increases the risk of a tubal pregnancy is most likely to inhibit which one of the following actions?
Transport of the ovum from ovary to uterus
657
Delayed ovulation, as a cause of tubal pregnancy, would most likely be associated with delayed secretion of which of the following hormones?
Luteinizing hormone
658
When the environmental temperature is 33° C, vasodilation of cutaneous blood vessels helps to regulate the body temperature of a human by:
Radiating excess body heat into the environment
659
Kidney failure during severe dehydration is most likely due to:
Inadequate blood volume for effective filtration
660
People who are born without sweat glands are likely to die of heat stroke in the tropics. This indicates that, under tropical conditions, the human body may:
Gain, rather than lose, heat by radiation
661
When viewing an X ray of the bones of a leg, a doctor can tell if the patient is a growing child, because the X ray shows:
Cartilaginous areas in the long bones
662
The outer layers of human skin are composed of dead cells impregnated with keratin and oil, which make the epidermis relatively impermeable to water, yet humans sweat freely in hot temperatures. This occurs because
Sweat glands have special channels through the skin
663
Remember peptide is for ____ and phosphodiester is for ___!
Peptide = protein; phosphodiester = DNA
664
What is the process of phagocytosis?
Bacteria uptaken by phagosome, combined with lysosome to become phagolysosome, digests/hydrolyzes the material (phagocytosis = a type of endocytosis)
665
Where does the electron transport chain/citric acid cycle take place?
Electron transport chain = inner mitochondrial membrane; citric acid cycle = mitochondrial matrix
666
What is the best experimental method to analyze the effect of a gene deletion on the rate of histone acetylation?
Western blot (histone = fully folded protein, would be analyzed by WB)
667
Vasopressin regulates the insertion of aquaporins into the apical membranes of the epithelial cells of which renal structure?
Collecting duct
668
What is the difference between a prion and a virion?
Virion = entire virus particle; prion = infectious (misfolded) protein
669
Internalization of viral particles through endocytosis is mediated by:
Endosomes
670
The precursor of EGP is translated from a transcript that has had one nontemplated nucleotide added to the open reading frame. This change does not create or eliminate a stop codon. Compared with the protein sGP, which is produced from the unedited transcript, EGP most likely has the same primary:
Amino-terminal sequence as sGP, but a different primary carboxy-terminal sequence (mutation would probably occur at the C terminal)
671
In humans, eggs and sperm are most similar with respect to:
Genome size
672
What are centrosomes made of?
Microtubules
673
Lytic granules are generally released from CTLs when the T-cell receptors on these cells bind specifically to:
Viral antigens presented on the surface of virus-infected cells
674
Where are the variable regions of an antibody?
The ends of the antibody
675
Where in the human male reproductive system do the gametes become motile and capable of fertilization?
Epididymis
676
According to the cross-bridge model of muscle contraction, the muscles stiffen after death because ATP is unavailable to bind and directly release:
The myosin head from the actin filament
677
Do muscle cells go through mitosis?
NO
678
What is the excitation-contraction coupling in skeletal muscle?
Troponin and tropomyosin are usually in a complex that biocks actin binding unless Ca2+, which is stored in sarcoplasmic reticulum until ACh in the NMJ causes a depolarization (Ca2+ causes troponin to remove tropomyosin, which reveals myosin binding sites)
679
What is the sliding filament model of muscle contraction?
To cause contraction, actin must unbind to a new binding site, relax then contract -> Step 1 = cross-bridge formation (actin and myosin bound to ADP), Step 2 = powerstroke (low-energy conformation, ADP released from actin bc myosin head pulls actin towards it), Step 3 = ATP binding releases head from current binding site, Step 4 = ATP hydrolysis is required to change the myosin into its cocked form, which allows it to contract
680
D-Glucose and D-mannose are epimers of each other, meaning that these sugars are examples of:
Diastereomers
681
What is the net distribution of charge across the cell membrane due to the activity of Na+/K+ ATPase?
Positive extracellular, negative intracellular
