UWorld Biology Flashcards
(102 cards)
1
Q
A woman with low serum cortisol due to partial adrenal dysfunction is treated with high doses of a synthetic cortisol analogue. According to Figure 2, treatment with a cortisol analogue will most likely cause this patient’s serum level of endogenous cortisol to:
A
Decrease.
Adrenal cortex synthesizes cortisol. If theres a high amount, cortisol inhibits the Hypothalamus to stop producing CRH which stops the anterior pituitary from producing ACTH
2
Q
A drug that blocks the release of adrenocorticotropic hormone from the anterior pituitary would most likely:
A.decrease secretion of cortisol from the adrenal cortex.
B.decrease secretion of thyroid-stimulating hormone from the anterior pituitary.
C.increase secretion of oxytocin from the posterior pituitary.
D.increase secretion of calcitonin from the thyroid.
A
A.decrease secretion of cortisol from the adrenal cortex.
3
Q
Which statement best describes the characteristics of hormones secreted from the pituitary gland?
A.Hormones secreted from the posterior pituitary are synthesized in the hypothalamus.
B.Hormones secreted from the posterior pituitary act on other endocrine glands.
C.Hormones secreted from the anterior pituitary only act directly on nonendocrine tissues.
D.Hormones secreted from the anterior pituitary are released by depolarization of the nerve terminals.
A
A.Hormones secreted from the posterior pituitary are synthesized in the hypothalamus.
4
Q
Hormones secreted from the hypothalamus to the anterior pituitary are released into the ________
A
hypophyseal portal system - a network of capillaries that enables small quantities of hormones secreted from the hypothalamus to directly reach the anterior pituitary without being diluted in the circulation
5
Q
Posterior pituitary hormones are synthesized where?
A
In hypothalamic neurons and are then transported down the axon to the axon terminals in the posterior pituitary, where they are stored. The secretion of stored hormones in the posterior pituitary are mediated by APs that cause exocytosis of neurosecretory vesicles
6
Q
A
pancreas and pituitary gland, respectively
7
Q
As the two anatomical divisions of the adrenal gland, the adrenal cortex and adrenal medulla share a common feature in that both:
A.synthesize steroid hormones.
B.release signaling molecules into lymph vessels.
C.regulate the synthesis of red blood cells.
D.secrete hormones that alter blood pressure.
A
D.secrete hormones that alter blood pressure.
Adrenal medulla secretes amino acid (peptide hormones) such as NE and EPI
Adrenal cortex secretes steroid hormones such as glucocorticoids and mineralcorticoids (INCREASES BP)
8
Q
The adrenal ______ secretes the hormones cortisol and aldosterone, and the adrenal ______ secretes the hormones epinephrine and norepinephrine.
A
Cortex
Medulla
9
Q
Patients with CAH exhibit hypoglycemia due to numerous endocrine abnormalities. In healthy individuals, hypoglycemia will trigger an increase in the serum level of:
insulin.
epinephrine.
glucagon.
A.I only
B.II only
C.I and III only
D.II and III only
A
D.II and III only
When blood glucose levels are low (eg, during periods of fasting), the hormone glucagon is secreted from the alpha cells of the pancreas, and the autonomic nervous system promotes the release of epinephrine and norepinephrine by the adrenal medulla.
Epinephrine and norepinephrine also promote glycogenolysis. Therefore, the overall effect of glucagon, epinephrine, and norepinephrine is to promote the synthesis of glucose and its release into the systemic circulation, thereby correcting the low serum level of glucose.
10
Q
Intraperitoneal injection of insulin would cause the peptide hormone to enter the bloodstream and exert its effect on target cells by:
A.acting as a second messenger.
B.diffusing through the plasma membrane.
C.binding an extracellular receptor.
D.disassociating from a carrier protein.
A
C.binding an extracellular receptor.
11
Q
After a meal, the body is in an energy-rich state (ie, high concentrations of glucose and lipids); as a result, the hormone leptin is released by ____________ to trigger feelings of satiety by communicating to the hypothalamus in the brain that the stomach is full, thereby suppressing appetite.
A
white adipose tissue
12
Q
Which of the following is a potential complication of secondary hyperparathyroidism?
A.Decreased bone mineralization
B.Decreased osteoclast activity
C.Increased osteoblast activity
D.Increased cortical bone mass
A
A.Decreased bone mineralization
PTH increases blood calcium - high osteoclast activity
13
Q
In response to increased plasma calcium concentration, the peptide hormone calcitonin is secreted by the
A
thyroid gland
14
Q
A student analyzing actively dividing cells under the microscope finds that each daughter cell contains half the number of chromosomes as the parent cell. Given this, these cells most likely contain all of the following EXCEPT:
A.peroxisomes.
B.nuclear pore proteins.
C.single-stranded genomic material.
D.microtubules.
A
C.single-stranded genomic material.
microtubules form the cytoskeleton - shape of the cell
15
Q
Plasmodium falciparum is a protozoan parasite known to cause malaria, an illness characterized by fever, chills, and flu-like symptoms. Which of the following is the most likely reason why P. falciparum would be classified as a eukaryotic organism?
A.It is able to reproduce sexually.
B.It has a mechanism for intron splicing.
C.It has a cell wall.
D.It has a cell membrane.
A
B.It has a mechanism for intron splicing.
eukaryotic cells are unique in that they have membrane-bound organelles as well as a mechanism for intron splicing by the spliceosome.
16
Q
A pathogen identified in a patient’s blood sample is found to lack a phospholipid bilayer. Therefore, any medications used to treat the disease caused by this pathogen would most likely be classified as:
A.antiprotozoal drugs.
B.antifungal drugs.
C.antiviral drugs.
D.antibacterial drugs.
A
C.antiviral drugs.
bacteria and eukaryotes have phospholipid bilayers
17
Q
E. coli K-12, a normal bacterial strain of the human microbiota, is able to cause disease by inducing enterocyte lesions after it is grown in media with EHEC bacteria that contain the F factor plasmid. What process most likely granted virulence to E. coli K-12?
A.Transformation
B.Transduction
C.Conjugation
D.Transfection
A
C.Conjugation
Transformation is the cellular uptake of foreign DNA from the environment.
Transduction involves DNA transfer from one bacterial cell to another by a bacteriophage (a virus that infects bacteria).
18
Q
Which of the following is most likely to be found within the cell membranes of intestinal epithelial cells?
A.Peptidoglycan
B.Cholesterol
C.Cytoskeletal filaments
D.Cellulose
A
B.Cholesterol
In addition to phospholipids, animal cell plasma membranes also contain cholesterol, glycolipids (lipids with attached sugar groups), glycoproteins (proteins with attached sugar groups), and other proteins.
Cholesterol, which is found in eukaryotic but not prokaryotic cell membranes
Cytoskeletal filaments are found in the cytoplasm of cells
19
Q
Which step(s) of the viral life cycle would most likely occur in lytic phages?
Injection of viral genetic material into the bacterial host
Integration of viral DNA into the bacterial genome
Degradation of the host genome
A.I only
B.III only
C.I and II only
D.I and III only
A
D.I and III only
Lytic: Attachment, injection, host genome degradation, synthesis of viral progeny, virions released due to lysozymes degrading host cell wall
In contrast, phages with a lysogenic life cycle integrate their genome with the host genome and replicate as the cell divides.
20
Q
A student adds 5 bacterial cells to a test tube containing fresh medium and incubates it for 3 hours at 37°C. If the bacterial population shows an initial lag phase of 20 minutes followed by a doubling time of 40 minutes, what is the approximate number of bacterial cells present at the end of the incubation period? (Note: Assume unrestricted growth during incubation.)
A.20 cells
B.40 cells
C.80 cells
D.160 cells
A
C.80 cells
21
Q
Assume a single-celled organism was discovered in water above 100°C. On closer inspection, it is determined that this organism was previously classified under the Archaea domain. Given this information, this organism most likely has:
A.a peptidoglycan layer in its cell wall.
B.a circular chromosome.
C.telomeres.
D.an endoplasmic reticulum.
A
B.a circular chromosome.
Like bacteria, archaea are unicellular (single-celled), have a circular chromosome, have no membrane-bound organelles or nucleus, and reproduce asexually via binary fission.
22
Q
Researchers are studying a single-celled pathogen. Which experimental method would be LEAST effective for determining whether the pathogen is prokaryotic or eukaryotic?
A.Analyzing the cells for the number of origins of replication
B.Exposing the pathogen to a fluorescent antimitochondrial antibody
C.Testing the pathogen for ribosome size
D.Assessing the pathogen for the presence of pyruvate in the cytoplasm
A
D.Assessing the pathogen for the presence of pyruvate in the cytoplasm
23
Q
Which of the following is true concerning transmembrane proteins?
A.They localize primarily in low-cholesterol environments known as lipid rafts.
B.They are held statically in place by cytoskeletal components.
C.They are able to interact only with the phospholipids on the outer leaflet of the cell membrane.
D.They can migrate laterally through the phospholipid-rich environment of the cell membrane.
A
D.They can migrate laterally through the phospholipid-rich environment of the cell membrane.
24
Q
As it matures, the endosomal lumen becomes acidified relative to the cytosol. Protons from the cytosol most likely enter the endosomal lumen by which of the following processes?
A.Simple diffusion
B.Facilitated diffusion
C.Passive transport
D.Active transport
A
D.Active transport since its acidic in the cytosol it needs to go against gradient
25
Microtubules make up:
## Footnote
A.ribosomes.
B.centrioles.
C.cilia.
D.centromeres.
B.centrioles.
26
**which of the following best explains how mitochondrial genes differed from eukaryotic genes prior to gene transfer? Mitochondrial genes were:**
A.interspersed with noncoding sequences.
B.located on chromosomes without telomeres.
C.present on a single-stranded DNA genome.
D.associated with histones.
B.located on chromosomes without telomeres.
circular DNA
27
**Ponyfish cells containing P. leiognathi symbionts were exposed to a spindle fiber toxin that inhibits microtubule polymerization. Given this information, which of the following would most likely result as a consequence of toxin exposure?**
A.P. leiognathi daughter cells with multiple copies of the Cu/Zn SOD gene
B.Ponyfish daughter cells containing the same copy number of the Cu/Zn SOD gene
C.Delayed separation of P. leiognathi cells during binary fission
D.Nondisjunction in somatic ponyfish cells undergoing nuclear division
The mitotic spindle begins to form when centrosomes (microtubule-organizing centers consisting of a pair of centrioles) start migrating to opposite poles of the cell and microtubule filaments grow from them, resulting in spindle fibers.
D.Nondisjunction in somatic ponyfish cells undergoing nuclear division
28
**In anaerobic environments, P. leiognathi can produce energy by using an inorganic final electron acceptor other than oxygen in the electron transport chain. Under anaerobic conditions, which of the following is NOT active in ponyfish cells but active in P. leiognathi?**
A.Glycolysis
B.Gluconeogenesis
C.Fermentation
D.ATP synthase
D.ATP synthase
29
**The reduced virulence of lac+ S. typhimurium has been correlated with an inability to generate the torque that turns the flagellum. Which structure in the flagellum is most likely being affected by lac genes?**
A.Hook
B.Filament
C.Basal body
D.Cell membrane
C.Basal body
the filament propels bacterium, hook transmits force, basal body works as a motor
30
**Scientists studying evolution in yeast found that a certain species underwent a reduction in chromosome number with no loss of coding information. Given this, which of the following mechanisms best explains how this reduction in chromosome number may have occurred?**
End-to-end fusion of two chromosomes followed by inactivation of one centromere on the newly formed chromosome
Breakage of a chromosome at the centromere and fusion of the two resulting chromosomal portions to the ends of other chromosomes
Transfer of a DNA sequence from one chromosomal arm to a different chromosomal arm
A.I only
B.II only
C.I and II only
D.I and III only
C.I and II only
end-to-end (telomere-to-telomere) fusion of two chromosomes and inactivation of one of the centromeres. This fusion would initially generate a larger chromosome with two centromeres, and inactivation of one of these centromeres would produce a single new chromosome, reducing the chromosome number in the cell by one (Number I).
breakage of a chromosome at the centromere and fusion of each chromosomal portion to the ends of other chromosomes. This initial breakage would result in two individual chromosomal portions. Fusion of these portions to other chromosomes would cause the original chromosome to be lost, also reducing the overall chromosome number in the cell by one
31
**Assume bacteria are infected with a vector containing HBV genetic material. This vector has been shown to introduce its genomic content into bacterial cells without fully gaining entry into the bacterial cytoplasm. Based on this information, the vector is most likely a:**
A.prion.
B.bacterium.
C.viroid.
D.bacteriophage.
D.bacteriophage.
32
Which organ synthesizes bile? Which stores it?
Liver synthesizes
Gallbladder stores it
33
Consequently, bile salts break down large lipid globules into smaller droplets (micelles) in a process known as \_\_\_\_\_\_\_
Emulsification
these lipids have increased SA on which pancreatic lipase can act on
34
The peritoneum is composed of two membranes that line the abdomen: the _______ layer, which lines the abdominal wall, and the _______ layer, which covers the abdominal organs.
parietal
visceral
**The peritoneal cavity is found within the abdomen and contains organs such as the liver, stomach, and intestines.**
35
**Stenosis is the abnormal narrowing of a tubular structure in the body, such as a blood vessel. Stenosis of the afferent arterioles in the kidney would be expected to:**
A.decrease the glomerular filtration rate.
B.increase blood flow to the glomeruli.
C.decrease resistance in the afferent arterioles.
D.increase output of urine.
A.decrease the glomerular filtration rate.
36
**Cirrhosis of the liver is characterized by hepatic cell death, tissue scarring, and altered liver function. All of the following would be disrupted by cirrhosis of the liver EXCEPT:**
A.the production of ketone bodies.
B.the metabolism of most drugs.
C.the oncotic pressure within capillaries
D.the secretion of digestive proteolytic enzymes.
D.the secretion of digestive proteolytic enzymes.
Osmotic pressure within capillaries **is due to the presence of plasma proteins** that cannot easily cross the capillary membrane. Oncotic pressure causes a **"pulling force"** inside capillaries, which balances the pushing force of hydrostatic pressure, **helping keep fluid in the vasculature.** The majority of plasma proteins such as albumin are synthesized in the liver. Therefore, cirrhosis is expected to impact the production of plasma proteins, which in turn would affect oncotic pressure in the capillaries
37
Ketogenesis (synthesis of ketone bodies) occurs mainly in the ______ and plays a critical role in energy metabolism when glycogen stores are depleted and blood glucose levels become low. During times of fasting, \_\_\_\_\_\_\_within \_\_\_\_\_cells convert ______ into ketone bodies, which are then used by the brain to make ATP
liver
mitochondria within liver cells
Acetyl CoA
38
**Human cardiac muscle differs from skeletal muscle because it:**
A.appears striated.
B.requires acetylcholine to contract.
C.contains intercalated discs.
D.contains cells with multiple nuclei.
C.contains intercalated discs.
it doesnt require ACh to contract.
Cardiac muscle is under **involuntary control and is myogenic**, meaning that it does not require nervous system input to contract. Instead, specialized cells in the **sinoatrial node** spontaneously depolarize to produce electrical impulses that spread through the cardiac muscle via its intercalated discs.
39
**During muscle contraction, the power stroke is the pivoting motion of the myosin head that pulls the actin filament inward to shorten the sarcomere. Given this, which of the following events immediately precedes the power stroke?**
A.The binding of ATP to the myosin heads
B.The hydrolysis of myosin-bound ATP to ADP and Pi
C.The release of ADP and Pi from the myosin head
D.The binding of Ca2+ to tropomyosin
C.The release of ADP and Pi from the myosin head
40
In one of the four pathways, the transcription factor NF-kB is activated, which leads to increased expression of the proto-oncogene c-Fos.
## Footnote
**A student isolates the cellular components of OPCs in wild-type (WT) mice and in mutant (MT) mice exhibiting a single base substitution that causes reduced osteoclast activity. Western blot analysis is then performed to test for NF-kB and c-Fos expression in the cytoplasm and nucleus of OPCs isolated from these mice. The results of this analysis are shown below.**
**Which statement best explains these results?**
A.MT mice have a mutation that disables the ability of NF-kB to localize to the nucleus.
B.MT mice have a mutation that prevents c-Fos from interacting with NF-kB.
C.MT mice have a mutation in the DNA binding region of NF-kB.
D.MT mice have a mutation that prevents the transcription of c-Fos in OPCs.
A.MT mice have a mutation that disables the ability of NF-kB to localize to the nucleus.
Transcription factors are proteins that can alter gene expression by **binding DNA near gene promoter region**s to either increase or decrease the transcription of a target gene. Like all proteins, transcription factors are **translated in the cytoplasm** and must enter the nucleus (where DNA is stored) to influence gene expression. Transcription factors rely on their **nuclear localization sequence to gain nuclear entry.** The nuclear localization sequence is composed of amino acids and functions as a nuclear import tag that is recognized and bound by nuclear import proteins, **which facilitate the transport of transcription factors into the nucleus.**
**Transcription factors contain DNA binding regions that allow them to interact with DNA in the nucleus. A mutation in the DNA binding region of NF-kB would prevent it from interacting with DNA and increasing the expression of c-Fos. However, a mutation in this region would notprevent NF-kB from entering the nucleus.**
41
**A scientist claims that endurance training is an exercise method that can improve physical performance by inducing changes in type 1 skeletal muscle fibers that allow the fiber to perform aerobic respiration more efficiently to generate ATP. Given this, which of the following adaptations is most likely to occur in type 1 fibers in response to endurance training?**
Mitochondrial density of the muscle fibers increases
Capillary supply around the muscle fiber increases
Myoglobin concentration per muscle fiber increases
A.I only
B.I and II only
C.III only
D.I, II, and III
D.I, II, and III
Type 1 fibers are fatigue-resistant, contract slowly, and use aerobic respiration as their primary method of ATP production. Consequently, compared with glycolytic fibers, type 1 fibers are **much richer in mitochondria,** the site where many enzymes involved in aerobic respiration reside. Type 1 fibers also have access to a continuous supply of oxygen (the final electron acceptor of aerobic respiration) through an **extensive network of capillaries** that surround the muscle. In addition, type 1 fibers appear red under the microscope due to high concentrations of myoglobin, a red-pigmented, **oxygen-binding molecule that delivers oxygen to the muscle cell interior,** where the mitochondria are housed.
42
**Researchers analyzing gene expression in connective tissue samples are likely to obtain gene expression profiles for all of the following tissues EXCEPT:**
A.bone tissue.
B.blood tissue.
C.adipose tissue.
D.muscle tissue.
D.muscle tissue. - epithelial cells
43
Many cells in adult humans are arrested in the \_\_\_\_\_\_\_\_\_phase of the cell cycle
G0 (nondividing)
cardiac myocytes
neurons
44
\_\_\_\_\_\_\_\_\_ cells lining blood vessel
endothelial cells
45
The food eaten during a meal is first digested in the _______ and passed on as a semifluid mass (\_\_\_\_\_\_\_\_) into the small intestine.
stomach
chyme
46
The large intestine is composed of three subdivisions: the cecum, colon, and rectum.
The colon functions to absorb ____________ and additional _______ from the mass of undigested material.
As this is absorbed by the colon, the undigested material concentrates into \_\_\_\_\_\_\_\_\_, which is stored in the rectum for subsequent excretion.
electrolytes (eg, sodium, chloride)/ water
feces (waste matter)
47
**A physician determines that a patient has injured a connective tissue structure connecting two bones within the knee joint. Given this finding, the likely basis of the injury is damage to:**
A.skeletal muscle.
B.adipose tissue.
C.a tendon.
D.a ligament.
D.a ligament. Bone to bone (think ALC in knee bones)
Tendon - muscle to bone
48
\_\_\_\_\_\_\_\_\_\_\_\_ forms a concentration gradient within the loop of Henle that maximizes water reabsorption
Countercurrent multiplication
49
**Renal studies in mice have revealed that a mutation in various sodium transporters causes impaired active transport of NaCl from the filtrate within the loop of Henle to the medulla. If mice with wild-type sodium transporters were compared to mice with the mutated sodium transporters, the mutant mice would likely exhibit all of the following EXCEPT:**
A.decreased saltiness of the medulla.
B.decreased urine output.
C.decreased renal water reabsorption.
D.decreased blood pressure.
B.decreased urine output.
Studies in mice indicate that sodium transporter mutations impair active transport of NaCl from the loop of Henle into the medulla. Accordingly, compared to wild-type mice, mice with mutated sodium transporters would exhibit a decrease in both medullary salt concentration and water reabsorption (Choice C), a decrease in blood pressure (Choice D), and an increase in urine output (Choice B).
50
**The critical concentration of plasma glucose necessary to induce glycosuria is termed the renal threshold of glucose. Compared to untreated T2DM patients, the renal threshold of glucose in T2DM patients treated with canagliflozin is:**
A.higher by approximately 75 mg/dL.
B.higher by approximately 175 mg/dL
C.lower by approximately 115 mg/dL.
D.lower by approximately 300 mg/dL.
C.lower by approximately 115 mg/dL.
51
**Researchers hypothesized that administration of canagliflozin reduces blood pressure in patients with diabetes by increasing urine output and reducing total blood volume. A decrease in which of the following would also result in lowered blood pressure?**
Activation of the renin-angiotensin system
Production of aldosterone
Secretion of antidiuretic hormone
A.II only
B.III only
C.I and III only
D.I, II, and III
D.I, II, and III
52
Renal reabsorption of glucose is facilitated by sodium-glucose linked transporters (SGLTs), which are secondary active transport proteins located in the apical membrane of the proximal tubular cells in the kidney.
## Footnote
**SGLT transports glucose against its concentration gradient across the luminal membrane of the proximal tubule. The energy to drive this form of glucose transport is most likely directly provided by:**
A.an electrochemical Na+ gradient.
B.an action potential.
C.ATP hydrolysis.
D.simple diffusion of Na+ ions.
A.an electrochemical Na+ gradient.
53
**In individuals with glycosuria, glucose that is not reabsorbed in the proximal tubule next flows into which of the following nephron structures?**
A.The distal tubule
B.The collecting duct
C.The loop of Henle
D.Bowman's capsule
C.The loop of Henle
54
**In neurons, action potential propagation occurs along the axon. The analogous structure in skeletal muscle fibers that enables action potential propagation is the:**
A.actin filament.
B.transverse tubule.
C.motor endplate.
D.myelin sheath.
B.transverse tubule.
Muscle fiber action potentials propagate along the sarcolemma, the plasma membrane of the muscle fiber. The sarcolemma burrows deep into the muscle fiber, forming hollow structures known as transverse (T) tubules. Action potentials propagate along T-tubules just as they propagate along the superficial sarcolemma, resulting in the rapid and complete depolarization of the muscle fiber. This promotes calcium release from the sarcoplasmic reticulum, leading to muscle fiber contraction.
55
**Dehydration caused by frequent loose stools is often observed in patients with certain diseases of the gastrointestinal (GI) tract. Given this, which of the following treatments would be most effective in treating this symptom?**
A.Use of drugs that increase smooth muscle contractions throughout the GI tract
B.Use of drugs that decrease glucose reabsorption from the small intestine
C.Use of drugs that increase activity of the parasympathetic nervous system
D.Use of drugs that decrease the luminal secretion of chloride ions from intestinal epithelial cells
D.Use of drugs that decrease the luminal secretion of chloride ions from intestinal epithelial cells
56
The ability of a resting sarcomere to contract is dependent on the existence of an overlap between actin and myosin filaments and the presence of a gap between the ends of the actin filaments and the M-line. Given this, which of the following diagrams best represents a resting sarcomere with the potential to generate the greatest amount of contractile force?
A
57
**Osteoarthritis (OA) is a disorder marked by the deterioration of articular (hyaline) cartilage, the connective tissue lining the ends of bones at most movable joints. Repeated and abnormal joint stress can also cause the development of osteophytes, or bony growths, that form on the subchondral bone.**
## Footnote
**OA commonly affects large, weight-bearing joints of the lower extremities such as the knee and hip. Based on the passage, which of the following would occur in a patient with OA involving the knees?**
A.Deterioration of the yellow bone marrow in affected bones
B.Deposition of excess bone on the epiphyses of affected long bones
C.Reduction of hematopoiesis in the red marrow of affected bones
D.Degeneration of compact bone at the diaphysis of affected long bones
B.Deposition of excess bone on the epiphyses of affected long bones
The knee joint is the site where the femur and tibia meet. According to the passage, OA can result in the formation of osteophytes (bony growths) on the subchondral bone, which is the bone under the damaged articular cartilage. In other words, additional bone deposits on the epiphyses of the bones at the affected joint.
58
The eel was transported into seawater that had been treated with the volume marker phenol red. After 20 hours, the eel's gut contained 2.3 mL of fluid but showed a phenol red concentration equivalent to 12.3 mL of ingested seawater. Researchers found that the eel lost 2.3 g of weight due to urine output. They ultimately reported that the eel had lost all the seawater it absorbed through the gut via various mechanisms.
## Footnote
**Which of the following conclusions about the eel can be made based on the experiment in the passage? (Note: Water density is 1 g/mL.)**
A.The eel absorbed 12.3 mL of water through the gut.
B.The eel drank 10 mL of water.
C.The eel lost 7.7 mL of water extrarenally.
D.The eel excreted 4.6 mL of water renally.
C.The eel lost 7.7 mL of water extrarenally.
In the given scenario, it is reported that after 20 hours, the eel's gut contains 2.3 mL of fluid, but the gut concentration of phenol red is equivalent to the eel having ingested 12.3 mL of water. Therefore, the **eel absorbed 10 mL of water** through its gut (12.3 mL − 2.3 mL), and the researchers claim that all the absorbed water was subsequently lost.
Of the 10 mL absorbed, the passage states that the eel had a 2.3-g weight loss due to urine output. Because the density of water is 1 g/mL, a **2.3-g weight loss would be equivalent to 2.3 mL** being excreted as urine (renal water loss)
**Total water loss=renal water loss+extrarenal water loss**
10 mL=2.3 mL+extrarenal water loss
10 mL−2.3 mL=extrarenal water loss
10 mL–2.3 mL=7.7 mL
59
Researchers studying marine teleosts claim that the glomerular kidney (Sculpin) is 500 times as efficient as the aglomerular kidney (goosefish) in eliminating nontoxic substances. Similar amounts of nontoxic ferrocyanide are intramuscularly injected into a sculpin and a goosefish of comparable weight. Given this, which of the following tables showing renal elimination of ferrocyanide after 5 hours would support the researchers' claim?
D
The researchers' claim is that the glomerular kidney is 500 times as efficient as the aglomerular kidney in eliminating nontoxic substances. In the given scenario, a sculpin and a goosefish of comparable weight were injected with similar volumes of nontoxic ferrocyanide. The question asks for a result in the glomerular sculpin and aglomerular eel that would support the researchers' claim regarding kidney efficiency in glomerular and aglomerular species.
60
**A scientist proposed that ectopic endometrial cells contain extra copies of the VEGF gene. Given this information, which of the following techniques can be used to analyze VEGF gene count?**
DNA sequencing
Northern blot
Southern blot
A.I only
B.II only
C.I and III only
D.II and III only
C.I and III only
The Northern blot resembles the Southern blot but detects RNA, not DNA. Because mRNA is the product of DNA transcription, northern blots assess **gene expression within a tissue**. However, the level of mRNA expression may vary greatly depending on factors other than gene quantity (eg, transcription factor activity, chromatin structure). Therefore, mRNA levels do not directly correspond to gene count, and northern blotting could not be used to determine whether ectopic endometrial cells contain extra copies of the VEGF gene.
**DNA sequencing and Southern blotting are DNA assays that may be used to assess the _relative quantity of genes_ between tissue types. Northern blotting is an RNA assay used to assess _gene expression_ in different tissues.**
61
**Surgical removal of the ovaries is one treatment for endometriosis. Complete removal of the ovaries would most likely result in which of the following?**
A.Significant increase in bone mass
B.Degeneration of breast tissue
C.Severe immune system impairment
D.Increased frequency of menstruation
B.Degeneration of breast tissue
Surgical removal of the ovaries in women of reproductive age mimics the withdrawal of female sex hormones normally associated with **menopause**, the cessation of menstrual cycles that occurs around age 50. During menopause, production of **estrogen and progesterone within the ovaries declines** substantially, leading to numerous physiological changes. For example, the vaginal epithelium **dehydrates** (causing discomfort and impairing sexual activity), changes in mood (eg, irritability, **depression**) may occur, and the **reproductive organs and breasts shrink (atrophy**). Accordingly, these menopausal symptoms may occur in patients whose ovaries are removed for medical reasons (eg, endometriosis).
62
**The systemic blood pressure gradient ΔP is equal to the mean pressure of blood exiting the heart through arteries minus the mean pressure of blood returning to the heart through veins. The relationship of ΔP to cardiac output (CO) and vascular resistance (VR) is given by:**
ΔP=CO×VR
**Given this, which of the following physiological changes would cause increased VR within vessels of the circulatory system? (Note: Assume all other physiological factors remain constant.)**
A.Increased vasodilation of arteries
B.Heightened activity of the SA node
C.Reduced ventricular filling prior to contraction
D.Decreased arterial blood pressure
C.Reduced ventricular filling prior to contraction
ΔP/CO=VR
Consequently, an increase in ΔP or a decrease in CO would increase VR. Specifically, CO is dependent on both heart rate (number of times a person's heart beats per minute) and stroke volume (blood volume expelled per left ventricular contraction). Stroke volume depends on the amount of blood loaded into the left ventricle prior to contraction. Reduced ventricular filling would lead to less blood being expelled from the ventricle with each contraction and decreased CO. Given the relationship of VR to CO, decreased CO (in the absence of other physiological changes) would ultimately increase VR.
63
**As shown below, CO2 reacts with water in the blood to form H2CO3, a weak acid that can reversibly dissociate to form HCO3− and a free H+ ion.**
**CO2+H2O⇋H2CO3⇋HCO−3+H+**
**The patient is noted to have decreased pulmonary gas exchange. Given this, which of the following is most likely to occur in the patient's blood if this condition is left untreated?**
A.More H2CO3 will be produced and blood pH will decrease.
B.Less H2CO3 will be produced and blood pH will increase.
C.More H+ ions will be present and blood pH will increase.
D.Fewer H+ ions will be present and blood pH will decrease.
A.More H2CO3 will be produced and blood pH will decrease.
The patient is found to have decreased pulmonary gas exchange, indicating that **O2 uptake** into the blood and CO2 removal from the blood at the lungs is **decreased**. If left untreated, this condition will lead to **low O2 and high CO2** levels in the patient's blood. This will shift the equilibrium of the reaction described above to the right, increasing the production of H2CO3, which in turn will dissociate, thereby increasing the presence of both HCO3− and H+ ions in the blood. Increased levels of circulating **free H+ ions will lead to decreased blood pH**, a phenomenon known as respiratory acidosis
64
**the excess fluid in the patient's lungs is most likely caused by which of the following at the pulmonary sites of gas exchange?**
A.Increased protein concentration in the blood flowing through pulmonary capillaries
B.Decreased osmotic pressure in the interstitial fluid surrounding the pulmonary capillaries
C.Increased hydrostatic pressure within pulmonary capillaries
D.Decreased volume of blood flowing through the pulmonary capillaries
C.Increased hydrostatic pressure within pulmonary capillaries
As blood flow through a capillary increases, hydrostatic pressure exerted on the vessel walls also increases, leading to a higher rate of fluid leakage from the capillary into the interstitial space. If the rate of fluid leakage from capillaries exceeds the rate at which fluid is taken up by surrounding blood and lymph vessels, a higher volume of leaked fluid can build up in associated tissues (ie, edema).
X-rays revealed that the patient has excess fluid in his lungs (ie, pulmonary edema), a condition that may hinder oxygen and carbon dioxide exchange at the alveoli. Pulmonary edema would be due to an increased volume of blood flowing through pulmonary capillaries (Choice D), which causes an increase in hydrostatic pressureexerted on capillary walls. High hydrostatic pressure would increase the rate of fluid leakage into the interstitial space surrounding pulmonary capillaries, causing excess fluid accumulation in the lungs.
65
**During a parasitic infection, which of the following would most likely be responsible for phagocytosis of organisms and the release of histamine, respectively?**
A.Basophils, macrophages
B.Natural killer cells, T-cells
C.Macrophages, basophils
D.T-cells, natural killer cells
C.Macrophages, basophils
66
**Which of the following cell-cell junctions would help skin cells withstand mechanical stress by directly anchoring the intermediate filaments of adjacent cells?**
Desmosomes
Gap junctions
Tight junctions
A.I only
B.II only
C.I and III only
D.II and III only
A.I only
Tight junctions are cell-cell junctions that prevent water and solutes from diffusing between cells and across the epithelial cell layer.
67
**Compared with blood in the pulmonary veins, blood in the pulmonary arteries has higher concentrations of:**
O2
H+
CO2
A.I and II only
B.I and III only
C.II and III only
D.I, II, and III
C.II and III only
68
**One function of endothelial cells is to:**
A.contract to increase blood pressure.
B.line the inside of the gastrointestinal tract.
C.form clots at sites of vascular damage.
D.line the inside of blood vessels.
D.line the inside of blood vessels.
69
Emphysema is stated to cause the breakdown of alveolar walls, which would decrease total alveolar surface area.
## Footnote
**which of the following changes would be expected in a patient with signs of emphysema?**
A.Narrowing of the trachea
B.Less efficient gas exchange
C.Weakened diaphragm muscle
D.Overstretched pharyngeal tissues
B.Less efficient gas exchange
## Footnote
The majority of gas exchange occurs at the alveoli, which are located at the ends of the respiratory tract branches. The thin walls of the alveoli allow oxygen and carbon dioxide to diffuse into the bloodstream (and vice versa) through the pulmonary capillaries surrounding the alveolar sacs. The small size and sheer number of alveoli in the lungs provide an enormous surface area available for efficient gas exchange in healthy individuals.
Emphysema is stated to cause the breakdown of alveolar walls, which would decrease total alveolar surface area. Because the alveoli are the main site of gas exchange, less efficient gas exchange is expected because less air can be in contact with respiratory tissue.
70
**The regulation of respiratory rate is normally most sensitive to:**
A.PO2 in the blood.
B.PCO2 in the blood.
C.PO2 in the alveoli.
D.PCO2 in the alveoli.
B.PCO2 in the blood.
## Footnote
The regulation of respiratory rate is normally most sensitive to the pH of the blood, which is measured by the central and peripheral chemoreceptors. The central **chemoreceptors are located in the brain**, and the **peripheral chemoreceptors are located in the aortic and carotid arteries**. Blood pH is determined by the concentration of H+ (protons) in the blood, which is determined by the equilibrium of the bicarbonate buffer system:
**CO2+H2O⇋H2CO3⇋HCO−3+H+**
The equilibrium of this buffer system will shift due to changes to the partial pressure of CO2 in the blood. These chemoreceptors directly measure the [H+] in the blood, and therefore indirectly measure the PCO2 in the blood. This information is relayed to the respiratory center of the nervous system.
71
**During an asthma attack, temporary bronchoconstriction would have what effect on blood pH, and what would be the expected homeostatic response?**
A.Respiratory acidosis and an increased respiratory rate
B.Respiratory acidosis and a decreased respiratory rate
C.Respiratory alkalosis and an increased respiratory rate
D.Respiratory alkalosis and a decreased respiratory rate
A.Respiratory acidosis and an increased respiratory rate
constriction = less O2 = more CO2 and H+ = more acidic
72
**The inflation of the lungs in normal inspiration involves:**
**Contraction of the diaphragm**
**Reduction of intrapleural pressure**
**Elevation of the rib cage**
A.I and II only
B.I and III only
C.II and III only
D.I, II, and III
D.I, II, and III
73
**A physician measures the arterial blood pressure of a patient while she is resting and again while she is running on a treadmill. The results of these blood pressure tests are given in the table below.**
**Given this data, was arterial blood pressure during heart contraction higher while the patient was resting or while she was running?**
A.Resting, because her diastolic blood pressure was higher when at rest.
B.Resting, because her systolic blood pressure was higher when at rest.
C.Running, because her systolic blood pressure was higher while running.
D.Running, because her diastolic blood pressure was higher while running.
C.Running, because her systolic blood pressure was higher while running.
## Footnote
During the systole phase, the heart contracts and blood is forced from the heart into the arteries. This increased volume of blood flowing through the arteries on contraction of the heart exerts increased pressure (ie, hydrostatic pressure) on the arterial walls. Accordingly, arterial blood pressure is highestduring systole and is measured as the systolic blood pressure.
74
**A single diploid cell containing 46 chromosomes underwent meiosis and produced four daughter cells, two with 22 chromosomes and two with 24 chromosomes. An error in which of the following stages of meiosis would most likely explain this result?**
A.Metaphase II
B.Prophase II
C.Telophase I
D.Anaphase I
D.Anaphase I
75
**If a viral antigen were to bind to the receptors on the surface of a B lymphocyte, which of the following immune responses would NOT occur?**
A.Division of the B lymphocyte into cells that differentiate to secrete antibodies
B.Interaction of the B lymphocyte with other immune cells that stimulate B-lymphocyte proliferation
C.Secretion of toxins by the B lymphocyte that destroy nearby virus-infected cells
D.Proliferation of cells that can recognize the antigen more rapidly in the event of a future infection
C.Secretion of toxins by the B lymphocyte that destroy nearby virus-infected cells
76
**Individuals with beta-thalassemia are at risk for developing an enlarged spleen. The resulting impairment of spleen function in these individuals would NOT affect:**
A.immune responses against viral or bacterial infection.
B.regulation of blood glucose concentration.
C.removal of aged red blood cells from the circulation.
D.storage of red blood cells.
B.regulation of blood glucose concentration.
77
**A subset of aggressive cancers has a relatively high growth rate, leading to the formation of large tumors. An effective drug against fast-growing tumors would most likely NOT target which stage of the cell cycle?**
A.G0
B.G2
C.G2/M checkpoint
D.G1/S checkpoint
A.G0
Most cells in the human body are arrested in G0. However, cellular transition into G1prepares a cell for division and DNA synthesis (S phase). In the G2 phase, DNA is checked for errors and the cell ensures that sufficient organelles and cytoplasm are available for cell division. Subsequently, the cell divides in the M phase via mitosis and cytokinesis. Compounds that inhibit cell division typically target the cell cycle in phases G1 to M.
78
**In a neuron, mitochondrial biogenesis is believed to occur primarily in the cell body, but mitochondria are often positioned at the presynaptic terminal, a distal site with high metabolic demand. Given this information, which molecular mechanism is most likely responsible for mitochondrial transport from the cell body to the presynaptic terminal?**
A.Kinesin motors transport mitochondria along microtubules
B.Kinesin motors transport mitochondria along microfilaments
C.Dynein motors transport mitochondria along microfilaments
D.Dynein motors transport mitochondria along microtubules
A.Kinesin motors transport mitochondria along microtubules
## Footnote
Microtubules are structural cytoplasmic filaments composed of tubulin subunits. These filaments have a number of critical functions, **including serving as tracks for intracellular transport of organelles and vesicles.** The movement of intracellular cargo along microtubules is mediated by two motor proteins:
**Kinesin:** Moves intracellular cargo along microtubules in anterograde axonal transport (ie, away from the nucleus and toward distal sites).
**Dynein:** Participates in retrograde axonal transport of intracellular cargo (ie, from distal sites toward the nucleus) (Choice D).
79
**Human sperm and oocytes are substantially different in all of the following aspects EXCEPT:**
A.cell volume.
B.maturation stage at birth.
C.the contribution of chromosomes to a zygote.
D.the rate at which they are produced.
C.the contribution of chromosomes to a zygote.
80
**A subset of the culture was first exposed to the drug VX-680, which arrests cells upon completion of metaphase**
## Footnote
**Based on the passage, VX-680 most likely inhibits:**
A.synthesis of transcription factors.
B.replication of the cell's genome.
C.chromosome alignment on the metaphase plate.
D.migration of sister chromatids to opposite poles of the cell.
D.migration of sister chromatids to opposite poles of the cell.
inhibits anaphase which comes after metaphase
81
**In an isolated population of 10,000 rabbits, 900 are homozygous for a recessive mutant Sp1 allele. Given this, what is the percentage of rabbits in the population who carry the mutant Sp1 allele but do not express the mutant phenotype? (Note: Assume the population is in Hardy-Weinberg equilibrium.)**
A.9%
B.21%
C.42%
D.70%
C.42%
82
**If researchers were to artificially express the SRY gene in WT,XX female rabbit embryos, then these rabbits would most likely develop:**
A.male characteristics, because Sp1 expression would increase and induce testis development.
B.male characteristics, because expression of SRY would induce testis development.
C.female characteristics, because the ratio of X to Y chromosomes dictates the sex in mammalian organisms.
D.female characteristics, because X chromosome inactivation in WT,XX females is not affected by SRY expression.
B.male characteristics, because expression of SRY would induce testis development.
83
**A gene expression assay shows that the SRY gene is expressed in male embryos during the early stages of development. Which of the following best describes the DNA methylation pattern exhibited by the SRY gene in embryonic gonadal cells compared to embryonic cardiac cells?**
A.The SRY gene will have higher levels of methylation in embryonic gonadal cells.
B.The SRY gene will have lower levels of methylation in embryonic gonadal cells.
C.The SRY gene will have similar levels of methylation in both cell types.
D.The comparison cannot be performed as cardiac cells do not carry the SRYgene.
B.The SRY gene will have lower levels of methylation in embryonic gonadal cells.
84
**A woman carries an X-linked recessive allele for a disorder characterized by muscle degeneration but does not express this condition. If she has multiple offspring with an unaffected man, how many of the woman's children are expected to exhibit this degenerative disorder?**
A.All
B.Half
C.None
D.One-quarter
D.One-quarter
85
**The North American flying squirrel and the Draco lizard of Southeast Asia have both evolved a membrane between their limbs that allows them to glide between trees in their habitats. Given that the species are distantly related, which of the following patterns of evolution would explain the development of this anatomical structure in both organisms?**
Parallel evolution
Divergent evolution
Convergent evolution
A.I only
B.II only
C.III only
D.I and II only
C.III only
Accordingly, the flying squirrel and Draco lizard have a distant evolutionary relationship, yet both have evolved an anatomical structure for gliding between trees. Because they both live in tree-dense habitats, it is likely that both species independently acquired a membrane between their limbs to adapt to similar environmental pressures and improve their chances of survival. For example, enhanced mobility or "gliding" between trees may have simplified foraging for food or aided in predator avoidance. Because the evolution of this feature occurred independently in these two very distantly related species, this is an example of convergent evolution
**Parallel evolution** occurs when **two more closely related species** (ie, descended from a more recent common ancestor) continue to evolve the same characteristics to adapt to similar environments.
**Divergent evolution** occurs when two species descended from a recent common ancestor **inhabit contrasting environments** and evolve distinct characteristics that allow them to better adapt to their differing environmental pressures.
86
**A skin graft candidate with full-thickness burns on approximately 50% of the total BSA is at risk for all of the following EXCEPT:**
A.extensive fluid loss.
B.bacterial infection.
C.increased sensitivity to touch.
D.vitamin D deficiency.
C.increased sensitivity to touch.
87
**What physiological change occurs in the skin of control subjects during Heat acclimation exercise?**
A.Enhanced contraction of arteriole smooth muscle
B.Enhanced relaxation of arteriole smooth muscle
C.Enhanced contraction of arrector pili muscles due to parasympathetic activation
D.Enhanced contraction of arrector pili muscles due to sympathetic activation
B.Enhanced relaxation of arteriole smooth muscle
D is when youre cold
88
The cheetahs that survived the environmental catastrophe that occurred 12,000 years ago are at greater risk of extinction because of:
A.naturally selected changes in allele frequencies.
B.random changes in allele frequencies.
C.changes in allele frequencies due to migration.
D.changes in allele frequencies due to random mating.
B.random changes in allele frequencies.
According to the passage, cheetahs experienced a catastrophic event that drastically reduced their population size; this is known as **a bottleneck event.** Bottlenecks (due to environmental events or human action) greatly **reduce the genetic diversity** of a population. Consequently, the smaller population of cheetahs has a reduced ability to buffer the negative **impacts of random changes in allele frequencies** (genetic drift) that may result in extinction.
**Natural selection is an evolutionary mechanism by which only beneficial alleles are selected for while unfavorable traits are selected against.**
89
**Assume that a subgroup of Namibian cheetahs exclusively hunt prey that weigh more than 100 kg. The individuals that make up this subgroup possess larger claws and teeth compared to average Namibian cheetahs and retain the ability to naturally mate with them. These morphological and behavioral changes reflect:**
A.the selection of average over extreme phenotypes.
B.how extreme characteristics are favored over average ones.
C.diversification of characteristics to better fill an ecological niche.
D.a new species.
C.diversification of characteristics to better fill an ecological niche.
**Adaptive radiation** is the process of diversifying characteristics in a subgroup of individuals from a single species. Adaptive radiation reduces intraspecific competition, the competition for resources by members of a single species. As a result, **fitness is improved for the entire species** because the subgroup has a new role within an ecological community (niche) that is different from the rest of the species. **Adaptive radiation can eventually lead to speciation, or the formation of a new species, if the subgroup continues to diverge.**
90
It is believed that around 12,000 years ago, Namibian cheetahs experienced an environmental catastrophe that drastically reduced their population. The small number of surviving cheetahs began mating with one another, which led to severe inbreeding depression. Over time, the offspring of subsequent generations exhibited decreased fitness, reduced fecundity (number of offspring), and sustained a loss of major histocompatibility complex (MHC) allele diversity
## Footnote
**If wild Namibian cheetahs continue breeding as described in the passage, what is most likely to occur to their population size in the long term?**
A.Increased population size with equal sex ratio
B.A sharp increase followed by a slight decrease in population size
C.Elimination of the Namibian cheetah species
D.Stable population size consisting of mostly females
C.Elimination of the Namibian cheetah species
91
the __________ region determines antibody class and function by dictating which body cells and proteins the antibody can interact with in order to facilitate antigen destruction
constant
92
The passage states that LFA-1 is located on the surface of leukocytes (white blood cells).
## Footnote
**According to the passage, cells containing the LFA-1 complex on their cell membranes most likely originate in which of the following tissues?**
A.Spleen
B.Thymus
C.Bone marrow
D.Lymph nodes
C.Bone marrow
Leukocytes include lymphocytes, neutrophils, eosinophils, basophils, and monocytes. All of the aforementioned cells originate in the bone marrow. Therefore, cells expressing LFA-1 on their surface originate from the bone marrow and not from the spleen, thymus, or lymph nodes.
The thymus is a lymphoid organ that serves as the site for T cell maturation
The spleen is an abdominal organ that functions to filter blood, store erythrocytes, and destroy old erythrocytes; it is also the site of B cell maturation.
93
**A gene regulating tail length in bobtail cats has a genetic variation at a single locus, where organisms can have an allele that produces long tails (L) or an allele that produces short tails (l). A male cat homozygous for short tail length (ll) was mated with a female cat homozygous for long tail length (LL). The tail lengths of the parents and offspring were recorded below.**
**A scientist concludes that the alleles regulating tail length in these cats exhibit incomplete dominance. Do the data support this conclusion?**
A.No, because all offspring have longer tails than the father's.
B.No, because all offspring inherited both types of alleles for tail length.
C.Yes, because the tail lengths of some offspring are longer than the tail lengths of other offspring.
D.Yes, because the offspring have tail lengths longer than the father's but shorter than the mother's.
D.Yes, because the offspring have tail lengths longer than the father's but shorter than the mother's.
94
**Following digestion in the small intestine, certain lipids are absorbed by intestinal epithelial cells and packaged into large droplets. These lipid droplets are released from intestinal epithelial cells and transported into the lymphatic system to ultimately drain into a large vein near the heart. Which series shows the order in which these lipid droplets are transported from the intestine to the bloodstream?**
A.Lymph capillaries → interstitial fluid → lymph vessels → lymph duct → vein
B.Interstitial fluid → lymph vessels → lymph duct → lymph capillaries → vein
C.Interstitial fluid → lymph capillaries → lymph vessels → lymph duct → vein
D.Lymph capillaries → interstitial fluid → lymph duct → lymph vessels → vein
C.Interstitial fluid → lymph capillaries → lymph vessels → lymph duct → vein
95
**Bacteria are removed from lymph and blood in the:**
A.spleen and bone marrow, respectively.
B.lymph nodes and spleen, respectively.
C.bone marrow and lymph nodes, respectively.
D.lymph vessels and thymus, respectively.
B.lymph nodes and spleen, respectively.
96
Transcription factors can upregulate or downregulate transcription by influencing the ability of (RNA or DNA) polymerase to bind to a promoter
RNA
97
Q3
B
In DNA synthesis, the template strand is **always complementary** to the new strand being synthesized. complementary strands always align **antiparallel**.
It stated the template was an RNA molecule, so it will contain Uracil instead of thymine
98
6
D
99
Q7
C
100
9
A
101
11
also
cldnk Produces a transcript 915BP
A
102
