BIO CHEM FROM BOOK Flashcards
(138 cards)
1
Q
Which of the following represents the most reduced form of carbon?
R-CH3 R-COOH R-CHO R-CH2OH CO2
A
R-CH3
2
Q
The Km (Michaelis constant) of an enzyme for a substrate is defined operationally as
half the substrate concentration at which the reaction rate is maximal
the substrate concentration at which the reaction rate is half maximal
the dissociation constant of the enzymesubstrate complex
the dissociation constant of the enzymeproduct complex
the rate constant of the reaction at saturation
A
the substrate concentration at which the reaction rate is half maximal
3
Q
Dinitrophenol (DNP) uncouples mitochondrial electron transport from oxidative phosphorylation by
dissipating the proton gradient
inhibiting cytochrome oxidase
dissociating the F0 and F1 units of the
ATP synthase complex
binding irreversibly to ubiquinone
blocking the adenine nucleotide carrier
(ATP/ADP exchanger)
A
dissipating the proton gradient (B) inhibiting cytochrome oxidase
4
Q
Most of the dry mass in the trunk of a tree was originally derived from
the soil light energy amino acids CO2 glucose
A
the soil
5
Q
Which of the following cell compartments is associated with a protein skeleton composed of lamins?
Chloroplast Basement membrane Mitochondrion Nucleus Peroxisome
A
Nucleus
6
Q
Initiation of mitogenesis by epidermal growth factor and depolarization of the membrane of a skeletal muscle cell by acetylcholine are similar in that each
involves, as an essential early step, an ion flux across the plasma-membrane receptor of the responding cell
requires a ligand-mediated conformational change in a plasma-membrane receptor of the responding cell
requires activation of a G protein on the cytoplasmic face of the plasma membrane in the responding cell
is mediated by phosphorylation of the ligand receptor in the responding cell
completes its primary task by direct activation of specific regulatory DNA sequences in the
nucleus of the responding cell
A
is mediated by phosphorylation of the ligand receptor in the responding cell
7
Q
The principal site of peptide neurohormone biosynthesis is the
nucleus rough endoplasmic reticulum dendrite postsynaptic density synaptic vesicle
A
rough endoplasmic reticulum
8
Q
A previously unknown organism that lacks a nuclear membrane and mitochondria has just been discovered. Which of the following would this organism most likely possess?
Lysosomes Cilia Ribosomes Endoplasmic reticulum Chloroplasts
A
Cilia
9
Q
Drugs that either stabilize or depolymerize microtubules can be used in cancer chemo- therapy. Which of the following is correct concerning such drugs?
They stimulate the immune system.
They prevent chromatin condensation.
They prevent movement of tumor cells into other tissues.
They interfere with mitosis.
They interfere with endocytosis.
A
They prevent movement of tumor cells into other tissues.
10
Q
If the genetic code consisted of four bases per codon rather than three, the maximum number of unique amino acids that could be encoded would be
16 64 128 256 512
A
256
11
Q
In humans, the Barr body is an
active X chromosome in females active X chromosome in males inactive Y chromosome in males inactive Y chromosome in females inactive X chromosome in females
A
inactive Y chromosome in females
12
Q
Which of the following types of molecules is always found in virions?
Lipid Protein Carbohydrate DNA RNA
A
RNA
13
Q
An RNA-dependent RNA polymerase is likely to be present in the virion of a
(A) DNA virus that multiplies in the cytoplasm
(B) DNA virus that multiplies in the nucleus
(C) minus-strand RNA virus
(D) plus-strand RNA virus
(E) transforming virus
A
DNA virus that multiplies in the nucleus
14
Q
In E. coli, the inability of the lac repressor to bind an inducer would result in
no substantial synthesis of -galactosidase
constitutive synthesis of -galactosidase
inducible synthesis of -galactosidase
synthesis of inactive -galactosidase
synthesis of -galactosidase only in the absence of lactose
A
inducible synthesis of -galactosidase
15
Q
If sucrose and monosodium glutamate (MSG) are added to a vinegar and oil salad dressing and shaken, the mixture will eventually separate into two phases of different density and polarity. Where will most of the sucrose and the MSG be located following phase separation?
Both will concentrate in the vinegar.
Both will concentrate in the oil.
Sucrose will concentrate in the oil and MSG will concentrate in the vinegar.
Sucrose will concentrate in the vinegar and MSG will concentrate in the oil.
A
Both will concentrate in the vinegar
16
Q
A major advantage of monoclonal antibodies compared to polyclonal antibodies is that monoclonal antibodies
have identical binding sites that recognize a specific epitope
cross-link molecules that share antigenic sites
are more easily coupled with probes such as fluorescent dyes
have higher-affinity binding to antigens
can be produced against proteins that are immunogenic in rabbits
A
have identical binding sites that recognize a specific epitope
17
Q
The initial product of photosynthetic CO2 fixation in C3 plants is
glyceraldehyde 3-phosphate dihydroxyacetone phosphate 3-phosphoglycerate phosphoenolpyruvate 1,3-bisphosphoglycerate
A
glyceraldehyde 3-phosphate
18
Q
In which of the following systems is the entropy the greatest?
Water vapor
Liquid water at pH 7.0, 37°C
Water with sufficient acid added to lower the pH to 2.0
Supercooled water (liquid water at a temperature less than 0°C)
Ice
A
Water with sufficient acid added to lower the pH to 2.0
19
Q
Which enzyme is activated by phosphorylation?
Acetyl-CoA carboxylase Fructose-1,6-bisphosphatase Glycogen synthase Pyruvate kinase Fructose-2,6-bisphosphatase
A
Acetyl-CoA carboxylase
20
Q
All of the following statements about monomeric G proteins are true EXCEPT:
They are regulated by GTP-GDP exchange proteins.
They are regulated by GTPase activating proteins.
They regulate enzymes that synthesize cGMP.
They regulate vesicle formation.
They regulate vesicle fusion.
A
They regulate vesicle fusion.
21
Q
All of the following are known to be part of a signal transduction cascade EXCEPT
phosphorylation of fibronectin
dissociation of the components of a heterotrimeric G-protein
enzymatic breakdown of phosphatidyl inositol bisphosphate (PIP2)
elevation of intracellular [Ca2+]
activation of cGMP phosphodiesterase
A
enzymatic breakdown of phosphatidyl inositol bisphosphate (PIP2)
22
Q
Which of the following will result if the level of potassium ions in a solution bathing a nerve cell is raised tenfold while the cell is at its resting state?
The decrease in the normal K+ gradient will cause partial depolarization.
The amplification of the normal K+ gradient will cause partial hyperpolarization.
The added extracellular K+ will accelerate Na+/K+ pumping and cause partial depolarization.
The added extracellular K+ will cause ligand-gated ion channels to open.
The elevated K+ will promote Ca2+ channel opening and produce partial hyperpolarization
A
The decrease in the normal K+ gradient will cause partial depolarization.
23
Q
SNARE proteins are found in the membranes of all of the following compartments EXCEPT
Mitochondria Golgi complex Early endosome Endoplasmic reticulum Synaptic plasma membrane
A
Mitochondria
24
Q
Treatment of root tip meristem cells with the microtubule inhibitor colchicine results in all of the following EXCEPT
induction of polyploidy prevention of cytokinesis inhibition of mitotic spindle assembly cessation of DNA replication prevention of chromosome segregation
A
induction of polyploidy
25
25. Genes a, b, and c are widely spaced in the bacterial genome. Transducing phage from an a+ b+ c+ bacterium were used to infect a culture of a− b− c− cells, and b+ transductants were selected. Which of the following best describes the predicted genotypes of these transductants?
```
Mostly a− b+ c−
Mostly a− b+ c+
Mostly a+ b+ c+
Mostly a+ b+ c−
a+ b+ c+ and a− b+ c− in equal frequencies
```
Mostly a+ b+ c−
26
If a cell has one chromosome in excess of the normal number of chromosomes present in the nucleus, it is referred to as
```
aneuploid
polyploid
tetraploid
haploid
allotetraploid
```
aneuploid
27
Which of the following statements about retrotransposons is correct?
They transpose via an RNA intermediate.
They contain genes for ribosomal proteins.
They possess a gene for RNA-dependent RNA polymerase.
They possess genes that encode proteins that integrate RNA into chromosomes.
They are found only in bacteria.
They transpose via an RNA intermediate
28
When bacteria produce mammalian proteins, cDNA is used rather than genomic DNA. Which of the following is the best explanation?
It is easier to clone cDNA than genomic DNA of comparable size.
It is easier to clone RNA than DNA.
It is not possible to clone the entire coding region of the gene.
Most eukaryotic genes have introns that cannot be removed in bacteria.
Most eukaryotic gene promoters do not function in bacteria.
It is easier to clone cDNA than genomic DNA of comparable size.
29
A mutation deleting an upstream activating sequence for a single gene would be expected to be
```
polar
trans-dominant
cis-dominant
silent
revertible
```
silent
30
The difference between the molecular weight of sucrose and that of the sum of the molecular weights of its components (glucose and fructose) is
```
0
1
16
18
180
```
16
31
Proline disrupts -helical structure in proteins because it is
```
an acidic amino acid
an aromatic amino acid
an imino acid
a basic amino acid
a sulfur-containing amino acid
```
an imino acid
32
Glycogen phosphorylase exists in two forms in skeletal muscle. The active form, phosphorylase a, is generated from phosphorylase b by
reversible dimerization of phosphorylase b, triggered by calcium ion
proteolytic cleavage of a decapeptide from the N-terminus of phosphorylase b
protonation of the active-site histidine residue by a decrease in intracellular pH
ATP-dependent phosphorylation of a specific serine residue on each subunit
noncovalent binding of ATP to allosteric sites on phosphorylase b
protonation of the active-site histidine residue by a decrease in intracellular pH
33
An alpha-helical conformation of a globular protein in solution is best determined by which of the following?
```
Ultraviolet-visible absorbance spectroscopy
Fluorescence spectroscopy
Electron microscopy
Analytical ultracentrifugation
Circular dichroism
```
Analytical ultracentrifugation
34
The nucleoside adenosine exists in a protonated form with a pKa of 3.8. The percentage of the protonated form at pH 4.8 is closest to
```
1
9
50
91
99
```
99
35
Membrane carrier proteins differ from membrane channel proteins by which of the following characteristics?
Carrier proteins are glycoproteins, while channel proteins are lipoproteins.
Carrier proteins transport molecules down their electrochemical gradient, while channel proteins transport molecules against their electrochemical gradient.
Carrier proteins can mediate active transport, while channel proteins cannot.
Carrier proteins do not bind to the material transported, while channel proteins do.
Carrier proteins are synthesized on free cytoplasmic ribosomes, while channel proteins are synthesized on ribosomes bound to the endoplasmic reticulum.
Carrier proteins transport molecules down their electrochemical gradient, while channel proteins transport molecules against their electrochemical gradient
36
Particular RNAs that are important for development are located in distinct regions of the Drosophila embryo. This is most directly demonstrated by using
```
western blotting
northern blotting
in situ hybridization
in vitro translation
electroporation
```
in situ hybridization
37
Which of the following events can induce a transient arrest in the translation of a secretory protein?
Binding of a polysome to an ER receptor
Binding of SRP to an N-terminal signal sequence
Binding of snRNPs to the large ribosomal subunit
Presence of a stop-transfer sequence in the polypeptide
Cleavage of the signal sequence by signal peptidase
Binding of snRNPs to the large ribosomal subunit
38
The common pathway of entry into the endoplasmic reticulum (ER) of secretory, lysosomal, and plasma membrane proteins is best explained by which of the following?
Binding of their mRNAs to a special class of ribosomes attached to the ER
Addition of a common sorting signal to each type of protein after completion of synthesis
Addition of oligosaccharides to all three types of proteins
Presence of a signal sequence that targets each type of protein to the ER during synthesis
Presence of a zinc finger-binding domain in these three types of proteins
Addition of a common sorting signal to each type of protein after completion of synthesis
39
Eukaryotic cells with DNA damage often cease progression through the cell cycle until the damage is repaired. This type of control over the cell cycle is referred to as
```
proteosome control
damage control
checkpoint control
anticyclin control
transcriptional control
```
anticyclin control
40
A microarray is a large collection of specific DNA oligonucleotides spotted in a defined pattern on a microscope slide. What is the most useful experiment that can be done with such a tool?
Predicting the presence of specific metabolites in a cell
Comparing newly synthesized nuclear RNA with cytoplasmic RNA to locate introns
Comparing RNA produced under two different physiological conditions to understand patterns of gene expression
Comparing proteins produced under two different physiological conditions to understand their function
Evaluating the linkage relationships of genes
Comparing RNA produced under two different physiological conditions to understand patterns of gene expression
41
In vertebrate genes, transcription regulatory regions that contain CpG islands are inactivated by which CpG modification?
```
Methylation
Myristylation
Phosphorylation
Acetylation
Ubiquitination
```
Phosphorylation
42
All of the following are proteins within the core nucleosome particle EXCEPT
```
H1
H2A
H2B
H3
H4
```
H1
43
In a study of arginine biosynthesis in yeast, four mutant haploids requiring arginine (Arg−) were isolated. The Arg− haploids were fused in pairwise combinations to form diploids, whose requirement for arginine was tested. The results of the tests were that all diploid combinations yielded arginine prototrophs. How many different Arg genes are represented among the four mutants?
```
One
Two
Three
Four
Five
```
One
44
A set of genes from Bacillus subtilis that encode the proteins required for sporulation have conserved DNA sequences −35 and −10 nucleotides before the site of transcript initiation, although the sequence at −35 is different from that seen in most other genes from that species. Which of the following best explains this difference?
A novel sigma factor is required for transcription initiation at these genes.
The −35 sequence is the binding site for a repressor of transcription.
The replication of these genes requires a specifically modified DNA polymerase.
Translation of the mRNAs transcribed from these genes requires specific ribosomes that recognize a modified Shine-Dalgarno sequence.
Transcription of these genes is induced by cAMP.
Translation of the mRNAs transcribed from these genes requires specific ribosomes that recognize a modified Shine-Dalgarno sequence.
45
Acetyl CoA, the cytoplasmic substrate for fatty acid synthesis, is formed in mitochondria. The inner mitochondrial membrane is impermeable to acetyl CoA. Which of the following compounds is the form in which the carbon of acetyl CoA is transported to the cytoplasm?
```
Malate
Acetate
Citrate
Pyruvate
Glucose
```
T(°C) pKw
0 14.94 25 14.00
50 13.28
75 12.71
Malate
46
The ion product for liquid water, Kw, varies with temperature (T), as indicated by the change in pKw shown in the table above. The definition of neutrality is [H+] = [OH−]. Which of the following is the pH of water at neutrality at 50°C ?
6. 35 (B) 6.64
7. 00
7. 40
13. 28
7.00
47
Which of the following groups of enzymes are unique to the Calvin cycle?
Ribulose bisphosphate carboxylase, phosphoribulokinase, and sedoheptulose
1,7-bisphosphatase
Ribose 5-phosphate isomerase, epimerase, and aldolase
Glyceraldehyde 3-phosphate dehydrogenase, phosphofructokinase, and phosphoenolpyruvate carboxylase
Phosphoglycolate phosphatase, glycerol kinase, and serine synthetase
Sucrose synthase, hexokinase, and glucose
6-phosphate dehydrogenase
Ribose 5-phosphate isomerase, epimerase, and aldolase
48
Which of the following best describes the hyperchromicity of DNA?
The shift in UV absorbance to longer wavelengths upon denaturation
The shift in UV absorbance to shorter wavelengths upon hydrolysis
The shift in UV absorbance to longer wavelengths upon annealing (forming double strands)
The increase in absorbance at 260 nm upon annealing
The increase in absorbance at 260 nm upon denaturation
The shift in UV absorbance to longer wavelengths upon denaturation
49
Isopentenyl pyrophosphate is a precursor of which of the following?
I. Cholesterol
II. Farnesyl groups on proteins
III. Steroid hormones
I, II, and III
I, II, and III
50
Cytokinesis in animal cells is caused by
the sliding movements of a band of microtubules around the circumference of the cell
the contraction of a band of actin filaments around the circumference of the cell
the movement of the mitotic spindle fibers
endocytosis of the plasma membrane around the equator of the cell
fusion of cytoplasmic membrane vesicles at the equator of the cell
fusion of cytoplasmic membrane vesicles at the equator of the cell
51
The synthesis of mRNA’s that encode the proteins of eukaryotic ribosomes occurs in the
```
cytoplasm
nuclear envelope
nucleolus
euchromatin
heterochromatin
```
nuclear envelope
52
Which of the following is NOT a consequence of increased cellular levels of cAMP?
Activation of a kinase cascade
Activation of the transducin G-protein
Increased phosphorylation of glycogen phosphorylase
Inhibition of glycogen synthesis
Dissociation of the cAMP-dependent protein kinase tetramer
Inhibition of glycogen synthesis
53
The KDEL sequence, found on luminal proteins of the ER, is responsible for
translocation of proteins into the ER lumen
insertion of proteins into the membrane of the ER
quality control in the ER
recognition by signal peptidase of the signal sequence
retrieval of ER luminal proteins from the Golgi
insertion of proteins into the membrane of the ER
54
Cyclins are proteins involved in regulation of
cell-cycle protein kinases
circadian rhythms
synthesis of cAMP
membrane circulation via exocytosis and endocytosis
the cycling of tubulin subunits through microtubules
the cycling of tubulin subunits through microtubules
55
The uppermost figure above shows the locations of four genes on the genetic map of an organism; the lower figure shows the locations of the same four genes on a physical map derived from the nucleotide sequence of the DNA of that organism. The maps are not identical because
there is no relationship between the position of genes in a genetic map and their positions on the DNA
recombination frequencies per kb of DNA are not uniform throughout a chromosome
the farther apart two genes are, the more likely they are to recombine
the closer two genes are, the more likely they are to recombine
some genes contain introns
recombination frequencies per kb of DNA are not uniform throughout a chromosome
56
The karyotype of a triploid plant contains 72 chromosomes. How many chromosomes would the karyotype of a diploid plant of the same species contain?
```
24
48
49
71
96
```
48
57
The DNA from the bacteriophage X174 has a base composition of 25% A, 33% T, 24% G, and 18% C. Which of the following best explains this observation?
In viral genomes, the base pairing does not follow the standard Watson-Crick rules, and allows G-A and C-T base pairs.
In viral genomes, the base pairing does not follow the standard Watson-Crick rules, and allows G-T and C-A base pairs.
Viral genomes are linear and tolerate basepair mismatches.
Nucleic acids from viruses are tightly complexed with nucleic acid-binding proteins and so cannot base-pair with one another.
The genome of bacteriophage X174 is single-stranded
The genome of bacteriophage X174 is single-stranded
58
The GAL4 protein activates transcription from the GAL1 promoter in yeast. To bind to DNA, the protein utilizes a
```
heme group
transcriptional-activating domain
zinc-finger domain
transmembrane segment
signal peptide
```
zinc-finger domain
59
Active transposable elements have which of the following features?
I. Repeated sequences at the ends of the transposable element
II. Different numbers and chromosomal posi-tions in different species of a single genus
III. The ability to alter the phenotype of an
organism
```
I only
II only
I and II only
I and III only
I, II, and III
```
I, II, and III
60
Which of the following is NOT an anabolic product of nitrogen assimilation?
```
Glutamate
Glutamine
Asparagine
Aspartate
Urea
```
Urea
61
Consider the average in vivo turnover rates for proteins, DNA, and mRNA. Which of the following orders best describes the turnover rate from fastest (shortest average lifetime) to slowest (longest average lifetime)?
```
mRNA > DNA > proteins
mRNA > proteins > DNA
Proteins > mRNA > DNA
Proteins > DNA > mRNA
DNA > mRNA > proteins
```
mRNA > proteins > DNA
62
In glycolysis, the hydrolysis of phosphoenol pyruvate is thermodynamically driven by the highly exergonic enol-to-keto conversion of pyruvate. From the two half reactions shown below, what is the Go of the complete reaction?
61.9 kJ mol−1
29.9 kJ mol−1
−29.9 kJ mol−1
−61.9 kJ mol−1
−123.8 kJ mol−1
−61.9 kJ mol−1
63
Rhodopsin, -adrenergic receptors, and muscarinic acetylcholine receptors share which of the following features?
Each causes an inhibitory intracellular response.
Each activates a tyrosine kinase cascade.
Each is composed of an dimer.
Each functions through a heterotrimeric G-protein.
Each gates a cation channel.
Each functions through a heterotrimeric G-protein.
64
Retroviral oncogenes are probably aberrant forms of normal cellular genes that regulate cell proliferation. Which of the following gene products are LEAST likely to be encoded by an oncogene?
```
GTP-binding proteins
DNA-binding proteins
Transmembrane proteins
Capsid proteins
Tyrosine kinases
```
Capsid proteins
65
Which of the following best supports the endosymbiotic theory of the evolutionary origin of mitochondria?
Mitochondria, chloroplasts, and prokaryotes contain electron carriers.
Genes for mitochondrial pyruvate dehydrogenase subunits are found in the nuclear DNA.
Mitochondrial and bacterial ribosomal functions are inhibited by the same antibiotics.
The outer mitochondrial membrane contains the protein porin.
Many mitochondrial proteins are imported across both inner and outer membranes after translation on cytoplasmic ribosomes is completed.
Mitochondrial and bacterial ribosomal functions are inhibited by the same antibiotics
66
When the nucleus of a frog red blood cell, which does not replicate DNA, is transplanted into an enucleated frog egg, the egg goes through several cell divisions. Which of the following is the best interpretation for this phenomenon?
Isolated red-blood-cell nuclei synthesize DNA.
The nucleus plays no role in cell division.
An enucleated frog egg can divide.
Genes do not function during early cleavage.
The cytoplasm controls nuclear DNA synthesis.
The cytoplasm controls nuclear DNA synthesis.
67
The nuclear-synthesized poly-A sequence at the 3′ end of eukaryotic messenger RNA is
attached at random sequences within the 3′ non-translated region of a pre-mRNA
found also as a common feature in rRNA and tRNA
ranscribed from poly-T sequences in template
DNA
transcribed by RNA polymerase II
added after 3′ end cleavage of the pre-mRNA transcript
added after 3′ end cleavage of the pre-mRNA transcript
68
A silent mutation in a gene results in
no change in the nucleotide sequence of the mRNA encoded by the gene
no change in the amino acid sequence of the protein encoded by the gene
no expression of the protein encoded by the gene
an amino acid substitution that has a significant effect on the functional activity of the protein encoded by the gene
a shift of the translational reading frame
no change in the amino acid sequence of the protein encoded by the gene
69
Which of the following most accurately explains the cause for the abnormal numbers of chromosomes during human reproduction that can result in Down syndrome, Turner’s syndrome, or Klinefelter’s syndrome?
The occurrence of nondisjunction of homologous chromosomes during meiosis
The duplicative production of extra chromosomes during DNA replication
The abnormal pairing of nonhomologous chromosomes during prophase of meiosis I
The selective loss of particular chromosomes from the sex cells after formation of the mature gamete
The fusion of two sperm with one egg to provide an extra set of paternal chromosomes
The occurrence of nondisjunction of homologous chromosomes during meiosis
The occurrence of nondisjunction of homologous chromosomes during meiosis
70
The enzyme reverse transcriptase is useful in the generation of cDNA libraries for which of the following reasons?
It is sensitive to high temperatures and so can be readily “killed” by heat treatment when the reaction is completed.
It does not require a primer to initiate polymerization as do most DNA polymerases.
It is insensitive to high temperatures and so can survive the many cycles of heating required to perform the polymerase chain reaction.
It is an RNA-dependent DNA polymerase
It lacks the proofreading function of most DNA polymerases and so is able to utilize mRNA from mutated genes as a template
It is an RNA-dependent DNA polymerase
71
Gene rearrangements play a role in which of the following processes?
Adaptation to carbon source by bacteria
Surface antigen changes in trypanosomes
Sex determination in nematodes
Host range modification in bacteriophage T4
Segmentation during arthropod development
Surface antigen changes in trypanosomes
72
A mutant of E. coli with a heat-sensitive DNA ligase (25°C permissive, 37°C nonpermissive) has been used to show that DNA synthesis is discontinuous. Examination of DNA replication in the presence of [3H]-thymidine in the mutant would demonstrate which of following?
The accumulation of short segments of unlabeled DNA at 25°C and at 37°C
The accumulation of short segments of unlabeled DNA at 25°C but not at 37°C
The accumulation of short segments of radioactive DNA at 37°C but not at 25°C
The accumulation of short segments of radioactive DNA at 25°C but not at 37°C
The incorporation of short fragments of radioactive DNA into longer ones at 25°C and at 37°C
The accumulation of short segments of radioactive DNA at 37°C but not at 25°C
73
All of the following statements are true about damage by ultraviolet light to DNA in living cells EXCEPT:
The damage blocks normal DNA replication.
The most damaging wavelength is about 260 nm.
Covalent bonds are formed that join neighboring pyrimidines.
Neighboring phosphodiester bonds are cleaved.
Most cells can synthesize proteins capable of repairing UV damage.
Neighboring phosphodiester bonds are cleaved.
74
Which of the following best predicts the direction of a chemical reaction?
```
S (entropy change)
H (enthalpy change)
E (internal energy change)
G (Gibbs free energy change)
Eact (energy of activation)
```
G (Gibbs free energy change)
75
Thyroxine labeled with 131I is administered to a patient for the purpose of imaging the thyroid gland. The radioactive half-life of the isotope is 8 days. The biological half-life (the time re- quired for half of the compound to be eliminated from the body) is 2 days. The time at which 3/4 of the original radioactivity will no longer be detectable in the body is closest to
2. 0 days
3. 2 days
4. 0 days
4. 8 days
16. 0 days
3.2 days
76
The pH dependencies of Vmax and Km for an enzyme are shown above. These data are most consistent with the requirement for
```
a general base in catalysis
a general acid in catalysis
a dissociable cofactor in catalysis
a basic residue in substrate binding
an acidic residue in substrate binding
```
a general base in catalysis
77
A coenzyme required by some enzymes that transfer one-carbon groups is
```
pyridoxal phosphate
tetrahydrofolate
thiamine pyrophosphate
flavin adenine dinucleotide
nicotinamide adenine dinucleotide
```
tetrahydrofolate
78
Which of the following represents the sequence of electron flow in the light reactions of photosynthesis in higher plants?
H2O → photosystem I → photosystem II → NADP
H2O → photosystem II → photosystem I → NADP
H2O → photosystem II → photosystem I → ATP
NADPH → photosystem I → photosystem II → O2
Photosystem I → photosystem II → NADPH → O2
H2O → photosystem II → photosystem I → NADP
79
llosteric inhibition of an enzyme involves which of the following?
Binding of an inhibitor to a site other than the substrate binding site
Binding of an inhibitor competitively to the substrate binding site
Binding of an inhibitor noncompetitively to the substrate binding site
Cooperative binding of substrate to an enzyme with four or more subunits
Cooperative binding of substrate to an enzyme that does not deviate from normal MichaelisMenten kinetics
Binding of an inhibitor to a site other than the substrate binding site
Binding of an inhibitor to a site other than the substrate binding site
80
The ability of a cell to migrate on a substrate involves all of the following EXCEPT
formation and breakage of focal adhesions
assembly of an actin meshwork at the leading edge
WASp proteins
Arp2/3 complex proteins
connexin proteins
connexin proteins
connexin proteins
81
Correct statements concerning different members of the myosin family include which of the following?
I. Some are actin plus (barbed)-end motors
II. Some are actin minus (pointed)-end motors
III. Some are actin-depolymerizing proteins
I and II only
82
Which of the following cell junctions is responsible for metabolic coupling?
```
Tight junction
Gap junction
Adherens junction
Desmosome
Hemidesmosome
```
Gap junction
83
A dicentric chromosome is unstable because
it cannot resynthesize its telomeres during replication
it pairs with nonhomologous chromosomes in meiosis
it pairs with nonhomologous chromosomes in mitosis
it is often simultaneously drawn to opposing spindle
poles in mitosis
many of its genes are silenced
it is often simultaneously drawn to opposing spindle poles in mitosis
84
Which of the following statements about repetitive DNA is NOT true?
Repetitive DNA is associated with the centromeres and telomeres in higher eukaryotes.
Repetitive DNA is restricted to nontranscribed regions of the genome.
Repetitive DNA sequences are often found in tandem clusters throughout the genome.
Repetitive DNA was first detected because of its rapid reassociation kinetics.
Transposable elements can contribute to the repetitive DNA fraction.
Repetitive DNA is restricted to nontranscribed regions of the genome
85
Which of the following is NOT characteristic of a eukaryotic enhancer element?
Its activity is independent of its orientation (i.e., the sequence can be inverted without effect).
Its activity is dependent on its distance from the start site of transcription.
It may be found as far as 1 to 2 kilobases from the promoter.
It may be positioned at the 5′ end or the 3′ end of the gene.
It increases the level of transcription of genes under its control.
Its activity is dependent on its distance from the start site of transcription.
86
The glyoxylate cycle is found in plants and bacteria but not in animals. The lack of this cycle in animals results in the inability to
synthesize oxaloacetate from isocitrate
synthesize glutamate from malate
perform gluconeogenesis from amino acids
perform gluconeogenesis from fatty acids
perform CO2 fixation via the reverse citric acid cycle
perform gluconeogenesis from fatty acids
87
The urea cycle occurs in the
```
mitochondrion and cytoplasm
mitochondrion and lysosome
endoplasmic reticulum
Golgi complex
peroxisome
```
mitochondrion and cytoplasm
88
The units of the molar extinction coefficient are
L mole−1 cm−1
L mole cm−1
mole−1 cm−1
cm L−1 cm−1
mL mg−1 cm−1
L mole−1 cm−1
89
The Pasteur effect, a decrease in the rate of glucose consumption when anaerobically grown yeast cells are exposed to O2, can be attributed to
uncoupling of oxidative phosphorylation from electron transport
an increase in ADP and AMP concentrations due to ATP hydrolysis
a decreased ATP yield per glucose molecule
an inhibition of phosphofructokinase by ATP and citrate
an inhibition of phosphofructokinase by ATP and citrate
90
The equilibrium constant for the reaction catalyzed by malate dehydrogenase (malate to oxaloacetate) is
about 5.9 × 10−6. Which of the following best describes the situation in which malate is converted to
oxaloacetate during the citric acid (Krebs) cycle?
The reaction is exergonic under standard conditions in the direction of the citric acid cycle and this drives the reaction.
The next reaction of the cycle, citrate synthase, is highly exergonic and it pulls the malate dehydrogenase reaction forward by removing oxaloacetate.
Malate dehydrogenase catalyzes an irreversible reaction in the citric acid cycle.
Malate dehydrogenase changes the equilibrium constant for the reaction, allowing it to proceed rapidly.
Malate accumulates in the cell to such a high concentration that it pushes the reaction forward.
The next reaction of the cycle, citrate synthase, is highly exergonic and it pulls the malate dehydrogenase reaction forward by removing oxaloacetate.
es the reaction forward.
91
Which of the following reactions is anaplerotic (replenishes intermediate pools) for the citric acid cycle?
Oxaloacetate + GTP → phosphoenolpyruvate + CO2 + GDP
Malate + NAD+ → oxaloacetate + NADH + H+
Citrate + ATP + CoA → oxaloacetate + ADP + acetyl-CoA + Pi
Oxaloacetate + acetyl-CoA → citrate + CoA
Pyruvate + HCO3− + ATP → oxaloacetate + ADP + Pi + H+
Pyruvate + HCO3− + ATP → oxaloacetate + ADP + Pi + H+
92
Propagation of a regenerative action potential along an axon can be accelerated by which of the following?
```
A decrease in the transmembrane resistance
A decrease in the axoplasmic resistance
Reduced myelin wrapping
Shortened internodal lengths
Narrowing of the axon diameter
```
A decrease in the axoplasmic resistance
93
All of the following processes occur in the pathway leading to regulated protein secretion in animal cells EXCEPT
formation of transport vesicles from the rough endoplasmic reticulum
an increase in the concentration of cytosolic calcium ions prior to secretion
synthesis of an amino-terminal signal sequence
phosphorylation of a mannose residue in a glycoprotein
trimming of N-linked oligosaccharides
phosphorylation of a mannose residue in a glycoprotein
94
Which of the following events occurs first as a result of EGF binding to its receptor?
```
Activation of a serine/threonine kinase
Activation of a tyrosine phosphatase
Activation of a tyrosine kinase
Activation of a phospholipase
Activation of a GTPase
```
Activation of a tyrosine kinase
95
Mitosis and meiosis accomplish segregation of the replicated DNA to two or more daughter cells. Which of the following is characteristic of both mitosis and meiosis?
Chromosomes attach to spindle fibers composed of actin.
The resulting cells are diploid (2n).
The resulting cells are haploid (1n).
Spindle fibers attach to chromosomes at their kinetochores.
Chiasmata form between chromosome arms.
Spindle fibers attach to chromosomes at their kinetochores.
96
The increase in the number of nucleoli during oocyte development in the frog Xenopus laevis is the result of
```
accelerated cell division
rapid chromosome replication
rapid synthesis of transfer RNA
amplification of the ribosomal RNA genes
accumulation of yolk protein
```
amplification of the ribosomal RNA genes
97
In meiosis, an inversion in one member of a pair of homologous chromosomes will most likely lead to which of the following?
Nondisjunction of the affected chromosome
Chromosomes with duplications and deficiencies
Increased recombination frequency in the inverted region
Mispairing of the affected chromosome with a nonhomologous chromosome
Cellular arrest in meiotic prophase
Chromosomes with duplications and deficiencies
98
One important mechanism for maintaining sequence identity among the many copies of a gene within a tandem array is
```
unequal crossing-over
gene conversion
retrotransposition
deletion
inversion
```
gene conversion
99
Which of the following conditions is likely to interfere with the transfer of genetic material by conjugation in bacteria?
Pretreatment of the recipient cells with DNase
Pretreatment of the recipient cells by application of strong shearing forces
Treatment of the recipient cells with cycloheximide
Treatment of the mating cell pairs by application of strong shearing forces
Treatment of the mating cell pairs with RNase
Treatment of the mating cell pairs by application of strong shearing forces
100
The zymogen chymotrypsinogen is converted to active chymotrypsin by
```
binding of a necessary metal ion
reduction of a disulfide bond
proteolytic cleavage
phosphorylation of an amino acid side chain
the action of a signal peptide peptidase
```
proteolytic cleavage
101
How many grams of MgCl2 are required to prepare one liter of a 10-millimolar MgCl2 solution? (Atomic weight of Mg = 24.3 g; atomic weight of Cl = 35.5 g.)
0.59 g
0.95 g
59 g
95 g
950 g
0.95 g
102
108. Which of the following statements is true regarding the polysaccharides starch, glycogen, cellulose, and chitin?
All have 1→4 linkages.
Starch is built from a different monomer than are the others.
Each is built from a single type of monomer.
Only chitin has a core protein.
Chitin and cellulose differ from each other only in the extent of their branching.
Each is built from a single type of monomer.
103
All of the following statements about the fluid mosaic model of biological membranes are true EXCEPT:
Lipid molecules in the membrane readily undergo lateral diffusion.
Lipid molecules in the membrane readily undergo transverse (flip-flop) diffusion.
Integral membrane proteins can undergo lateral diffusion.
The saturated hydrocarbon chains of lipid molecules in the membrane undergo carbon-carbon bond rotation.
The transition temperature of a membrane is sensitive to the composition of the lipid molecules in the membrane.
Lipid molecules in the membrane readily undergo transverse (flip-flop) diffusion.
104
The primary action of steroid hormones is at the level of
```
RNA export from the nucleus
transcription
pre-mRNA splicing
mRNA degradation
gene rearrangement
```
transcription
105
The first metabolic intermediate that is common to the aerobic metabolism of glucose and fatty acids is
```
acetyl CoA
beta-hydroxybutyrate
pyruvate
citrate
glyceraldehyde 3-phosphate
```
acetyl CoA
106
In an operon regulated only by attenuation, a mutation causing oversynthesis of the gene products is most likely to be in the part of the DNA corresponding to the
```
operator
3′ terminal sequence of the RNA
5′ terminal sequence of the RNA
introns of the RNA
coding sequence for the trans activator
```
5′ terminal sequence of the RNA
107
Two protein sequences are compared by BLAST and produce an e value of e−100. This e value most likely signifies which of the following about the genes encoding these two proteins?
They function in the same tissue.
They have unrelated functions.
They are descended from a common ancestor.
They are derived from related species.
They encode proteins that form a dimeric complex.
They are descended from a common ancestor. (D) They are derived from related species.
108
The processes that lead to the synthesis of the functional light chain of an antibody molecule include
DNA rearrangement but no RNA splicing
DNA rearrangement but no gene duplication
DNA rearrangement but no protein processing
RNA splicing but no DNA rearrangement
gene duplication but no protein processing
DNA rearrangement but no gene duplication
109
A second mutation in the same gene restores the wild-type phenotype. This phenomenon is referred to as
```
intergenic complementation
gene conversion
synthetic enhancement
intragenic suppression
epistasis
```
intragenic suppression
110
During the gluconeogenic conversion of pyruvate into glucose in the liver, all of the following are involved EXCEPT
```
pyruvate carboxylase
phosphoenolpyruvate carboxylase
phosphoenolpyruvate carboxykinase
glucose 6-phosphatase
fructose 1,6-bisphosphatase
```
phosphoenolpyruvate carboxylase
111
Water is generally a good solvent for polar molecules and a poor solvent for nonpolar molecules. These solvent properties are best explained by
the high density of liquid water relative to polar solvents
the ability to form intermolecular hydrogen bonds
the density of solid water being less than the density of liquid water
high surface tension
high heat of vaporization
the ability to form intermolecular hydrogen bonds
112
Movement of plasma membrane receptors from the basolateral surface to the apical surface of polarized epithelial cells
```
Phagocytosis
Exocytosis
Endocytosis
Transcytosis
Apoptosis
```
Transcytosis
113
Up-regulation of glucose transporters at the plasma membrane
```
Phagocytosis
Exocytosis
Endocytosis
Transcytosis
Apoptosis
```
Exocytosis
114
Selective retrieval of cell-surface proteins for recycling or degradation
```
Phagocytosis
Exocytosis
Endocytosis
Transcytosis
Apoptosis
```
Endocytosis
115
Neurotransmitter release
```
Phagocytosis
Exocytosis
Endocytosis
Transcytosis
Apoptosis
```
Exocytos
116
The exchange of material between nonhomologous chromosomes
```
Transition
Transversion
Translocation
Tautomerization
Reversion
```
Translocation
117
The change from a mutant allele to a wild-type
allele
```
Transition
Transversion
Translocation
Tautomerization
Reversion
```
Reversion
118
Forms a Schiff-base linkage with the -amino group of lysine residues
```
Chymotrypsin
Cyanogen bromide
Iodoacetamide
Phenylglyoxal
Pyridoxal 5′-phosphate
```
Pyridoxal 5′-phosphate
119
Specifically cleaves polypeptides on the carboxyl side of methionine residues
```
Chymotrypsin
Cyanogen bromide
Iodoacetamide
Phenylglyoxal
Pyridoxal 5′-phosphate
```
Cyanogen bromide
120
Generally used as a sulfhydryl-modifying reagent
```
Chymotrypsin
Cyanogen bromide
Iodoacetamide
Phenylglyoxal
Pyridoxal 5′-phosphate
```
Iodoacetamide
121
Its assembly is inhibited by penicillin.
```
Thylakoid membrane
Nuclear lamina
Eubacterial cell wall
Plant cell wall
Endoplasmic reticulum
```
Eubacterial cell wall
122
It is formed from polymeric fibrils composed of cellulose cross-linked by pectin and hemicellulose.
```
Thylakoid membrane
Nuclear lamina
Eubacterial cell wall
Plant cell wall
Endoplasmic reticulum
```
Plant cell wall
123
It is the site of dolichol phosphate function.
```
Thylakoid membrane
Nuclear lamina
Eubacterial cell wall
Plant cell wall
Endoplasmic reticulum
```
Endoplasmic reticulum
124
Produces oligonucleotides that contain damaged bases
```
Photoreactivation
Excision repair
Recombination repair
SOS repair
Mismatch repair
```
Excision repair
Excision repair
125
Acts only on pyrimidine dimers
```
Photoreactivation
Excision repair
Recombination repair
SOS repair
Mismatch repair
```
Photoreactivation
126
Uses methyl groups to distinguish parental and daughter strands
```
Photoreactivation
Excision repair
Recombination repair
SOS repair
Mismatch repair
```
Mismatch repair
127
Is often mutagenic
```
Photoreactivation
Excision repair
Recombination repair
SOS repair
Mismatch repair
```
SOS repair
128
129
Involves exchange of sister strands
```
Photoreactivation
Excision repair
Recombination repair
SOS repair
Mismatch repair
```
Recombination repair
129
Donates electrons to mitochondrial cytochrome oxidase
```
Cytochrome c
Cytochrome b
Plastocyanin
Ubiquinone
Plastoquinone
```
Cytochrome c
130
Donates electrons to P700 of Photosystem I
```
Cytochrome c
Cytochrome b
Plastocyanin
Ubiquinone
Plastoquinone
```
Plastocyanin
131
Accepts electrons from mitochondrial NADH dehydrogenase
```
Cytochrome c
Cytochrome b
Plastocyanin
Ubiquinone
Plastoquinone
```
Ubiquinone
132
Catalyzes the hydrolytic removal of one phosphate group from a monosaccharide bisphosphate
```
Isomerase
Kinase
Ligase
Phosphatase
Oxidoreductase
```
Phosphatase
133
Catalyzes the transfer of a phosphoryl group to a nucleoside diphosphate
```
Isomerase
Kinase
Ligase
Phosphatase
Oxidoreductase
```
Kinase
134
Catalyzes the conversion of a ketosugar phosphate to the corresponding aldosugar phosphate
```
Isomerase
Kinase
Ligase
Phosphatase
Oxidoreductase
```
Isomerase
135
Possesses genes that may be integrated into the genome of an infected eukaryotic cell
```
E. coli
Yeast
Bacteriophage T4
Bacteriophage lambda
Adenovirus
```
Adenovirus
136
Can lysogenize bacteria
```
E. coli
Yeast
Bacteriophage T4
Bacteriophage lambda
Adenovirus
```
Bacteriophage lambda
137
In Drosophila melanogaster, cinnabar eye (cn) and vestigial wing (vg) are simple recessive traits. A female, heterozygous for both genes, was crossed with a male with cinnabar eyes and vestigial wings. The offspring resulting from this cross are listed in the table below.
```
Class Phenotype
I Wild type
II Cinnabar eye, wild-type wing
III Wild-type eye, vestigial wing
IV Cinnabar eye, vestigial wing Number
```
445 51
49 455
Recombinant phenotypes include which of the following classes?
```
IV only
I and IV only
II and III only
I, II, and III only
II, III, and IV only
```
From the data shown, the distance between the cn and vg genes is approximately
```
500 map units
100 map units
50 map units
10 map units
5 map units
```
If crossing-over were to occur in the male parent, the anticipated effect on phenotypic numbers would be
```
a decrease in class I
a decrease in class II
a decrease in class III
a decrease in class IV
no significant difference
```
If cn and vg were unlinked, what percent of the offspring would be expected to have either cinnabar eyes or vestigial wings or both?
```
100%
75%
50%
25%
6%
```
II and III only
10 map units
no significant difference
75%
138
END
END
