Cell Biology and Physiology Block 1
Examination 2
September 24, 2008
2. The energy released by catabolism is conserved in three types of molecule. Which of the
following is NOT one of the three types?
a. nucleoside triphosphates
b. fatty acids
c. reduced coenzymes
d. acetyl coenzyme A
4. Anaplerotic reactions of the TCA cycle are required to balance
a. the efflux of TCA intermediates that leave the cycle for other pathways.
b. the number of electrons that leave the cycle as NADH.
c. the acetyl CoA that enters pathways other than TCA.
d. the buildup of intermediates that occur prior to a positive ΔGo′ step.
7. Proteins that are targeted to the rough endoplasmic reticulum most likely
a. contain an N-terminal signal peptide.
b. are synthesized on free ribosomes.
c. are destined for the mitochondria.
d. contain formyl-methionine.
10. When the electron transfer chain and oxidative phosphorylation are both activated, the
TCA cycle also gets activated. The signals from the electron transfer chain and oxidative
phosphorylation that activate the TCA cycle are
a. ATP and NADH
b. NAD+ and ATP
c. ADP and NADH
d. NAD+ and ADP
14. In metabolism, “activation” of a metabolite refers to
a. addition of a catalyst
b. bypassing endergonic reactions in a pathway
c. bypassing the unreactive components of a pathway
d. converting the metabolite into a more reactive compound.
25. Which of the following would be an anabolic pathway?
a. The TCA cycle, where 2 moles of pyruvate are oxidized completely to CO2 and H2O.
b. Glycolysis, where 1 mole of glucose is oxidized to 2 moles of pyruvate.
c. Gluconeogenesis, where 1 mole of glucose is synthesized from 2 moles of pyruvate.
d. Fatty acid oxidation, where the fatty acid hydrocarbon chain is completely oxidized to
CO2 and H2O.
26. What is substrate level phosphorylation?
a. The use of ATP to phosphorylate a protein.
b. The formation of a high energy phosphate compound such as ATP without the use of O2.
c. The oxidation of a molecule resulting from the addition of a phosphate group.
d. The reduction of a molecule resulting from the addition of a phosphate group.
28. Twelve hours after consuming a meal, one is in the
a. fed state.
b. high-insulin state.
c. low glucagon state.
d. post-absorptive or basal state.
29. For the reaction A ↔ B, ΔGo′ is largely positive. Because of this
a. [A] is much smaller than [B].
b. [A] = [B]
c. [B] is much smaller the [A].
d. [B] = 0.
33. Hormones, like glucocorticoid and thyroid hormones, commonly affect gene
transcription by
a. binding to activation domains of DNA.
b. binding to enhancers.
c. changing the affinity of receptors for DNA regulatory sequences.
d. interfering with repressor binding.
38. Which of the following relationships is true regarding the free energy of high energy
phosphate molecules?
a. ATP > glucose 6-P > acetyl CoA
b. PEP > acetyl CoA > ATP
c. Glucose 6-P < UDP-glucose < 1,3-BPG
d. PEP < ATP < glucose 6-P
40. Two metabolites that make an oxidation-reduction pair are molecule A (Eo′ = -15 mV)
and molecule B (Eo′ = 10 mV). Electrons will readily flow
a. from molecule A to molecule B.
b. from molecule B to molecule A.
c. from neither molecule because these two species are in equilibrium.
d. from both molecules to the other, since they are a redox pair.
41. The TCA cycle
a. is overall endothermic.
b. produces 3 NADH, 1 FADH2 and 1 GTP during each full cycle.
c. removes two electrons from CoA in the process of accepting the acetyl group.
d. incorporates two net carbons during each cycle.
49. During the “fasted” state, adipose tissue
a. releases fatty acids.
b. stores fatty acids.
c. produces ketone bodies.
d. produces glucose.
50. Select the CORRECT statement:
a. ATP is synthesized in the intra-membrane space.
b. NADH transfers two electrons to Complex I one at a time.
c. The combined energy cost of synthesizing ATP and transporting ATP and ADP + Pi across
the mitochondrial membrane is approximately equivalent to the influx of four protons.
d. In resting mammals, approximately 80% of the oxygen consumed by mitochondria is
uncoupled by mitochondrial proton leakage for heat production.
52. Which of the following is (are) true when acetyl CoA levels are high in mitochondria?
a. Pyruvate is converted to oxaloacetate.
b. Pyruvate dehydrogenase is allosterically inhibited by acetyl CoA.
c. Acetyl CoA reacts with oxaloacetate to form citrate.
d. All of the above are true.
53. Which of the following TCA cycle reactions does NOT involve an oxidative
decarboxylation?
a. isocitrate to α-ketoglutarate.
b. malate to oxaloacetate.
c. α-ketoglutarate to succinylCoA
d. none of the above are oxidative decarboxylations.
55. Pyruvate dehydrogenase becomes inactive when phosphorylated by a specific kinase.
This is an example of what type of metabolic regulation?
a. an irreversible reaction.
b. a committed step.
c. hormonal regulation.
d. feedback inhibition.
68. During a long fast (weeks), the primary source of energy for the brain is
a. glucose.
b. fatty acids.
c. ketone bodies.
d. amino acids.
2007 EXAM 1
8. Heparin is a very effective anti-blood coagulant use to treat thrombosis (blood clots) and
to help control blood clotting during surgical procedures. Why type of molecule is heparin?
a. glycosoaminoglycan
b. monosaccharide
c. amino acid
d. fatty acid
10. CO2 can spontaneously cross lipid bilayers in either direction. This is an example of
a. facilitated diffusion.
b. simple diffusion.
c. active transport.
d. antiport.
11. Which of the following is NOT a function of proteoglycan molecules?
a. They act as a shock absorber in joint tissue.
b. They help protect the outer surface of cells as part of the extracellular matrix.
c. They help reduce blood sheer stresses on vascular endothelial cells.
d. They serve as identifying markers on red blood cells.
18. Which of the following is NOT a typical structural feature of proteoglycans?
a. They have long sequences of repeating glycosoaminoglycans.
b. The core protein is often attached to a heparin sulfate glycosoaminoglycan.
c. They are attached to the core protein via a serine residue.
d. They form a bottle-brush type of structure.
Questions 24-29 refer to the figure below, which depicts the insulin signaling cascade. The
lipid with the two phosphate groups is PI 4,5 bisphosphate. The proteins are: Ins = insulin,
IRS = insulin receptor substrate, PDK-1 = phosphoinositide-dependent kinase-1, and PKB =
protein kinase B.
24. Insulin
a. activates anabolic (synthesize proteins, grow, store energy) pathways.
b. activates catabolic (break down molecules for energy) pathways.
c. signals the fasting state.
d. is a steroid hormone.
25. The insulin receptor is an example of a
a. ligand-gated receptor.
b. receptor kinase.
c. G-protein coupled receptor.
d. steroid hormone receptor.
26. Insulin binding activates its target receptor by
a. entering the active site and catalyzing the enzymatic reaction.
b. acting as a cofactor for the enzymatic reaction.
c. inducing a conformational change in the receptor that activates its enzymatic activity.
d. phosphorylating the receptor.
27. What effect does PI 4,5 bisphosphate have on the proteins PDK and PKB?
a. no effect
b. it activates both proteins
c. it is phosphorylated by PDK and activates PKB
d. it prevents both proteins from binding to the membrane
28. The binding of the proteins PDK and PKB to PI 3,4,5 trisphosphate is
a. a typical enzyme-substrate interaction for both proteins.
b. controlled by specific weak interactions and biomolecular recognition.
c. not affected by the pH and ionic strength of the medium.
d. dependent on insulin remaining bound to its receptor for long periods.
29. Activated PKB dissociates from PI 3,4,5 trisphosphate because
a. PI 3,4,5 trisphosphate is negatively charged.
b. phosphorylation of PKB induces a structural change in PKB that decreases its affinity for
PI 3,4,5 trisphosphate.
c. insulin is no longer bound to its receptor.
d. PI 3,4,5 trisphosphate is a second messenger.
30. β-adrenergic receptors are G-protein coupled receptors. The second messenger
produced by this receptor cascade is
a. Ca2+.
b. IP3.
c. cAMP.*
d. PI 3,4,5 trisphosphate.
31. Reversible phosphorylation of an allosteric enzyme alters enzyme activity because
a. the phosphate binds to the active site, thereby changing the catalysis.
b. the enzyme adjusts its conformation to accommodate the addition or removal of the
phosphate group.*
c. phosphate groups have negative charges.
d. phosphate groups can form ionic interactions with other amino acid side chains.
40. Insulin signaling increases cellular Ca2+ levels via which second messenger?
a. Ca2+
b. IP3
c. cAMP
d. PI 3,4,5 trisphosphate
51. Steroid and thyroid hormone receptors usually affect
a. protein kinases.
b. cell death.
c. G-proteins.
d. gene transcription.
53. Which of the following cosubstrates is shown in its reduced form?
a. NAD+
b. FMN
c. NADPH
d. biotin
70. Potassium ion transport across a membrane is controlled by the electrochemical
potential, which means K+ ions will move spontaneously across the membrane from high
[K+] toward low [K+] until
a. the concentration of K+ ions is equal on both sides of the membrane.
b. until the voltage across the membrane is eliminated.
c. until the chemical force of the concentration difference across the membrane is balanced
by the opposite force of the voltage established by the movement of K+ ions across the
membrane.
d. all the above.
71. Which of the following cofactors participates in single carbon transfer reactions?
a. coenzyme A
b. tetrahydrofolate
c. lipoamide
d. pyridoxyl phosphate
73. Secondary active transport systems often use a pre-existing Na+ gradient across the
membrane to drive the active transport of a second molecule across a membrane. What
establishes the ion gradient?
a. a simple diffusion system.
b. a primary active transport system.
c. a facilitated diffusion system.
d. a secondary active transport system.
74. Which of the following cosubstrates participates in acyl transfer reactions?
a. coenzyme A
b. thiamine pyrophosphate
c. cobalamin
d. biotin
2007 EXAM 3
3. A medical student studied so hard for his / her biochemistry exam that he / she did not
eat for one whole day before the exam. What was the primary fuel source used for the
student’s red blood cells as he/she walked to the medical school to take the exam?
a. glucose
b. fatty acids
c. amino acids
d. cholesterol
e. pyruvate
4. For the reaction A à B, ΔGo′ is largely negative. Because of this
a. [B] = 0
b. [B] is much smaller than [A]
c. [A] is much smaller than [B]
d. [A] = 0
6. For most individuals, the blood glucagon level is controlled by ____________, whereas the
blood insulin level is controlled by ____________.
a. fasting; carbohydrate consumption
b. the blood insulin level; blood glucagon level
c. the blood insulin level; the blood glucose level
7. During times of fasting when the liver is producing glucose for the blood, this glucose
does not enter glycolysis in the liver cell because
a. it is phosphorylated and therefore can’t remain in the liver cell.
b. once it is released into the blood the glucose is used by another tissue before it comes
back to the liver.
c. liver hexokinase has a very low affinity for glucose, so the glucose does not get
phosphorylated to remain in the cell.
d. liver glucokinase has a very low affinity for glucose, so the glucose does not get
phosphorylated to remain in the cell.
11. Humans cannot convert acetyl CoA from even-chain fatty acid oxidation to glucose.
However, oxidation of odd-chain fatty acids can lead to glucose formation because
a. they produce one mole of propionyl CoA per mole of fatty acid oxidized.
b. their acetyl CoA can be converted directly to pyruvate.
c. gluconeogenesis occurs simultaneously with fatty acid oxidation.
d. the brain can utilize odd-chain fatty acids to make its own supply of glucose.
12. The primary agent of energy transduction in metabolic pathways is
a. the acetyl group
b. the electron
c. glucose
d. pyruvate
17. It is said that hexokinase commits glucose to the cell because
a. ATP is utilized during this reaction.
b. once formed, the product glucose 1-phosphate cannot leave the cell.
c. once formed, the product glucose 6-phosphate cannot leave the cell.
d. the eventual product of glycolysis, phosphoenolpyruvate, has such a high energy the cell
must use this molecule or risk losing the stored energy.
23. One week after an episode of bronchitis, a 7-year-old girl with insulin-dependent
diabetes mellitus (i.e., a deficiency of insulin) is brought to the emergency room in a coma.
Her breathing is rapid and deep, and her breath has a fruity odor. Her blood glucose is 37
mM (normal: 4-6 mM). The physician administers IV fluids that includes insulin among
other things. One effect of insulin in this situation would most likely be to stimulate
a. gluconeogenesis in the liver.
b. fatty acid release from adipose.
c. ketone body utilization in the brain.
d. glucose transport into muscle.
25. Which of the following shows the correct order of high energy phosphate molecules in
terms of least to greatest free energy potential?
a. acetyl CoA < ATP < glucose 6-P < PEP
b. glucose 6-P < acetyl CoA < ATP < PEP
c. acetyl CoA < glucose 6-P < ATP < PEP
d. glucose-6-P < ATP < acetyl CoA < PEP
26. During fasting, ATP levels are generally high due to the large amount of acetyl CoA
produced by fatty acid oxidation. Ignoring insulin and glucagon considerations, high ATP
helps to restrict catabolic activity by inhibiting
a. glycolysis.
b. the fatty acid oxidation.
c. the TCA cycle.
d. all the above.
28. Cells utilize high energy biomolecules because
a. they are easily made and store energy for later use.
b. they are formed by substrate-level phosphorylation, so the cell does not need oxygen to
synthesize them.
c. they provide the necessary free energy required to drive energetically unfavorable
reactions.
d. they possess chemical groups not found in enzyme active sites, allowing the enzyme to
carry out complex chemical reactions.
Questions 31 – 35 are based on the following scenario. A 4 year old girl has become
lethargic and has a swollen abdomen, and she has not eaten for over two days. The parents
take her to the emergency room. Physical examination shows the girl has massive
hepatomegaly (enlarged liver) and enlarged kidneys with normal spleen and heart.
Laboratory studies show she has extremely low blood sugar (hypoglycemia). Biopsy of liver
and muscle shows excess glycogen is present in the liver but essentially no glycogen is
present in muscle. A glycogen-related disease is suspected, but further tests reveal that the
glycogen phosphorylase and phosphoglucomutase enzymes are functional in the patient.
31. Why would a glycogen-related disease be suspected?
a. When blood sugar is low, glucagon is high and glycogen breakdown should be activated,
but glycogen levels in the liver are above normal.
b. Despite the low blood sugar, insulin is high which should activate glycogen synthesis in
the muscle, but muscle glycogen is depleted.
c. Liver glycogen levels are higher than normal, suggesting no glucose is going toward
glycogen synthesis but rather is directed into glycolysis for cellular energy needs.
d. Muscle glycogen levels are lower than normal, suggesting that muscle glucose should be
directed to replenishing the glycogen store, but it is apparently is not working.
32. Based on the fact that the patient’s blood sugar is low, why does it make sense that
muscle glycogen would be depleted?
a. It doesn’t make sense – if glycogen is abnormal, it should be abnormal to the same extent
in muscle and liver.
b. Due to the low blood glucose level, muscle glycogen was used to produce free glucose
units that were released into the blood for use by other tissues.
c. The patient must have exercised prior to his examination by the pediatrician, which
depleted the muscle glycogen stores.
d. Due to the low blood glucose level, muscle was getting no glucose to use as energy. It used
its own supply of glycogen to help meet its energy needs until it was all gone.
33. If glycogenolysis is not able to produce glucose for the body, what would be the primary
source of blood glucose for this patient?
a. glycolysis.
b. gluconeogenesis
c. muscle glycogen breakdown.
d. acetyl CoA from fatty acid oxidation.
34. A defect in which enzyme could explain the liver’s inability to supply glucose to the
blood?
a. glucose-6-phosphate dehydrogenase
b. phosphofructokinase-1
c. glycogen phosphorylase
d. glucose-6-phosphatase
35. If this patient is given an IV treatment containing glucose sufficient to raise her blood
glucose level to around 200 mg/dL, which of the following most likely happen?
a. Her pancreas will release insulin.
b. Her muscles will import glucose and regenerate their glycogen stores.
c. Her brain will take up the glucose and use it as the primary energy source.
d. All of the above are true.
37. What does it mean that the reactions malate to oxaloacetate and NAD+ to NADH are
coupled reactions for malate dehydrogenase?
a. That the energy required by the malate to oxaloacetate reaction can be obtained from the
electron transport chain via NADH.
b. That the NAD+ produced in another TCA cycle reaction can be used in this step.
c. That the protons liberated in this step can be used to drive ATP synthesis by the ATP
synthase.
d. That the two reactions occur simultaneously within the active site of the enzyme and one
reaction will not happen unless the other reaction also occurs.
38. A 50 year old man in his second post-operative day after an appendectomy has not
eaten since the day of his surgery. Which of the following enzymes is most likely in an
inactive state?
a. glycogen phosphorylase
b. glycogen phosphorylase kinase
c. glycogen synthase
d. phosphoenolpyruvate carboxykinase
41. Pyruvate carboxylase catalyzes the most important anaplerotic reaction which is
a. ATP-dependent carboxylation of pyruvate to malate.
b. GTP-dependent carboxylation of PEP to oxaloacetate.
c. NADPH-dependent reductive carboxylation of pyruvate to malate.
d. ATP-dependent carboxylation of pyruvate to oxaloacetate.
42. Fructose is metabolized using many of the same enzymes involved in glucose
metabolism. Why doesn’t fructose stimulate an insulin response?
a. It is glucose-6-phosphate that stimulates pancreatic β-cells to release insulin.
b. Blood fructose concentrations are never high enough to stimulate glucokinase to convert
fructose to glucose 6-phosphate.
c. Fructose is imported into cells using the GLUT5 transporter.
d. Aldolase B isn’t present in pancreas cells, which prevents fructose from being
phosphorylated, which prevents stimulation of an insulin response.
45. The oxidative decarboxylation of pyruvate to acetyl-CoA is catalyzed by
a. pyruvate carboxylase.
b. pyruvate decarboxylase.
c. pyruvate dehydrogenase complex.
d. acetyl CoA synthetase.
46. A patient fasted for approximately 18 hours, then consumed a protein-only meal. What
effect would this meal have on gluconeogenesis in the patient’s liver?
a. Gluconeogenesis would stop since the patient consumed a meal.
b. The dietary amino acids would be used as a starting material for gluconeogenesis instead
of amino acids donated from muscle.
c. The patient could supply glucose to the liver from glycogen instead of gluconeogenesis.
d. All the above are true.
47. Ketone bodies are utilized by the brain when
a. a person has been fasting between 4 and 12 hours.
b. the level of ketone bodies in the blood gets sufficiently high.
c. acetyl CoA levels start to decline during a fast.
d. a person consumes more fat than carbohydrate.
48. Two molecules that make an oxidation-reduction pair are molecule A (Eo′ = - 35 mV)
and molecule B (Eo′ = -100 mV). Electrons will readily flow
a. from molecule A to molecule B
b. from molecule B to molecule A
c. from neither molecule since both have a negative Eo′ value
d. away from both molecules since both have a negative Eo′ value
49. Muscle cells do not respond to glucagon. Which metabolic signal(s) stimulate(s)
glycogen breakdown in muscle?
a. epinephrine
b. AMP
c. Ca2+
d. All of the above are stimulatory.
51. Pyruvate carboxylase attaches a CO2 group onto pyruvate to make oxaloacetate. For this
to happen, one molecule of ATP must be split to ADP + Pi simultaneously. Knowing this,
which statement is TRUE regarding the conversion of pyruvate à oxaloacetate?
a. It is a substrate-level phosphorylation reaction.
b. Pyruvate carboxylase is a kinase.
c. ΔGo′ is positive for the reaction.
d. ΔGo′ is negative for the reaction.
52. Following a protein only meal (no carbohydrate), there is a small but short lived insulin
spike. What causes this small insulin response?
a. neuronal signaling
b. the small amount of glycogen in muscle protein.
c. the amino acid in the protein
d. glucose
54. Which of the following is a catabolic pathway?
a. Glycolysis, where 1 mole of glucose is oxidized to 2 moles of pyruvate.
b. The electron transport chain, where electrons are passed through a series of proteins to
establish a proton gradient.
c. Protein synthesis, where individual amino acids are used to make proteins.
d. Fatty acid synthesis, where acetyl CoA is used to make the fatty acid hydrocarbon chain
Questions 56 – 62 refer to the diagram below. You and your study partners are arguing
about what metabolic state this figure represents. You say it is the long fast state (7 days or
more) and your study partners say it is the short fast state (several hours). Answering the
following questions will help you resolve this argument. In all cases below, short fast means
several hours of fasting and long fast means seven days or more of fasting.
56. You and your study partners agree that the figure represents some form of a fasted state
because
a. the only glucose available to the system is coming from the liver.
b. fuel molecules are being mobilized from body stores.
c. muscle is not using glucose as fuel.
d. all of the above are true.
57. You argue that the figure can’t represent the short fast, because the muscle is shown
supplying only a small amount (dashed line) of amino acid to the liver for glucose
production. Why does muscle provide amino acids to the liver during times of fasting (long
or short)?
a. By decreasing muscle mass, the energy needs of muscle declines.
b. Amino acids are used as precursors for glucose synthesis in the liver.
c. Amino acids are used as fuel by the liver so that it doesn’t have to use other fuels.
d. Amino acids form part of the Cori cycle, which exchanges amino acids for glucose
between muscle and liver.
58. Why won’t muscle provide large amounts of amino acids to the liver during long fasts?
a. The gluconeogenesis-blood glucose level would continue to rise and stimulate an insulin
response.
b. Fatty acids would not be able to supply muscle with sufficient energy.
c. There could be a significant loss of muscle mass.
d. The brain would not be able to utilize ketone bodies because the muscle would need
them.
59. You argue that the brain is shown using ketone bodies as the main energy source,
whereas during short fasts the brain utilizes glucose as the primary fuel. You tell them that
the brain uses glucose during short fasts because
a. glucose is the preferred fuel source for brain.
b. liver can produce sufficient glucose for the blood to meet the glucose needs of brain and
all other tissues that rely on glucose as a sole energy source.
c. ketone bodies are produced during a short fast, but the concentration of ketone bodies in
the blood is not yet sufficiently high for brain to start using this fuel.
d. all the above are true for a short fast.
60. Your study partners argue that you can’t rule out the short fast state because the
adipose tissue is shown supplying fatty acids to liver and muscle, and glycerol to liver,
which also happens during the short fast state. True, you say, but you tell your partners that
during long fasts
a. muscle stops using ketone bodies for fuel, which allows the ketone bodies to be used
primarily by the brain.
b. muscle has switched to using to fatty acids as fuel, preserving the very small amount of
blood glucose for the brain and other tissues that rely solely on glucose as fuel.
c. fatty acids are mobilized out of the adipose tissue during long fasts when insulin levels are
still high.
d. the kidney is able to process the extra nitrogen that is produced in response to increased
fatty acid utilization.
61. Your study partners won’t relent. They say the figure shows clearly that excess nitrogen
is being eliminated by the kidney in the form of urea, which happens during short fasts. To
counter this, you point out that
a. the kidney cannot eliminate excess nitrogen as urea during long fasts, since the kidney
has no supply of glucose to use as fuel.
b. during long fasts excess nitrogen stays in the muscle to help re-synthesize amino acids
and rebuild muscle protein.
c. urea is actually a by-product of gluconeogenesis, which is significantly decreased during
long fasts.
d. nitrogen excretion as urea via the kidney is significantly decreased during long fasts
because much less muscle amino acid is being used to drive glucose production by the liver.
62. You win - your study partners believe you are correct! However, because they are sore
losers they say you didn’t account for the fact that the red blood cells are still using glucose
as an energy source, even though the blood glucose level is very small. No problem. You
simply tell them that red blood cells
a. can only produce lactate if they make pyruvate during glycolysis.
b. don’t have mitochondria, so they can only use glucose for ATP production.
c. don’t need much ATP during long fasts.
d. all the above are true.
64. Despite two largely endothermic reaction steps, the TCA cycle proceeds in a forward
direction because
a. the endothermic reactions are coupled to the breakdown of a high energy phosphate
molecule
b. the change in standard reduction potential for each reaction insures the electrons will
continue to move forward through the cycle.
c. the free energy of ATP is high enough to ensure the TCA cycle proceeds to completion.
d. overall the net free energy change of the TCA cycle is negative.
2006 EXAM 2
1. Some enzymes utilize cofactors because cofactors
a. alter the ΔGo’ for a reaction to accelerate the chemical reaction.
b. alter the Keq for a reaction and the cofactors provide a high concentration term.
c. slow down enzyme conformational changes by forming many additional weak
interactions.
d. provide chemical groups that allow the enzyme to carry out special chemistry not
possible with the common amino acid side chains.
2. Hypertonic solutions added to the extracellular fluid around a cell causes the cell to
shrink because
a. the higher osmolarity outside the cell causes water to leave the cell.
b. the lower osmolarity outside the cell causes water to leave the cell.
c. the higher osmolarity inside the cell causes water to leave the cell.
d. this activates the sodium pump.
3. Which of the following is not a steroid hormone?
a. cortisol
b. cholesterol
c. aldosterone
d. thyroid hormone
4. Proteoglycan molecules are ideal components of the extracellular matrix because
a. they are sponge-like and act as shock absorbers to protect the cell membrane from
mechanical stress.
b. their small size allows them to fit in the tight space between the various extracellular
matrix components.
c. their structure makes them very rigid and strong, which is needed for protecting the
surface of the cell membrane.
d. they absorb a lot of water, keeping the membrane surface properly hydrated.
7. Carbohydrate groups attached to proteins or lipids are almost always
a. found outside the cell or on the external face of the plasma membrane.
b. located inside the cell on the inner face of the plasma membrane.
c. attached to asparagine residues.
d. composed of cerebrosides or gangliosides.
8. A fluid sample from a patient has an ion composition of 15 mM Na+, 120 mM K+ and 20
mM Cl-. This fluid is most likely
a. extracellular fluid.
b. intracellular fluid.
c. interstitial fluid.
d. plasma volume fluid.
9. Signal cascades generated by G-protein coupled receptors are terminated by
a. degrading the second messenger molecules.
b. dissociating the hormone from the receptor.
c. dephosphorylating target molecules.
d. All of the above.
Questions 11-13 refer to the figure below, which depicts amino acid transport into an
intestinal epithelial cell from the small intestine lumen and amino acid transport out of the
intestinal epithelial cell into the blood stream via the portal vein. For the purposes of this
question, the concentration of amino acid in the intestinal lumen and portal vein is lower
than the amino acid concentration inside the epithelial cell
11. The source of energy used to transport the amino acid into the cell against its
concentration gradient is most likely
a. the Na+ gradient.
b. the amino acid gradient.
c. the transport protein.
d. ATP.
12. If the sodium pump suddenly becomes inactive and fails to function, amino acid import
into the cell from the intestinal lumen will
a. not be affected.
b. decrease as the Na+ gradient decreases.
c. increase as more and more Na+ enters the cell.
d. reverse direction and amino acids will leave the cell.
13. Long after a meal, when the small intestine is empty, the concentration of amino acids in
the intestinal lumen and inside the epithelial cell is lower than the amino acid concentration
in the blood. What prevents amino acids from leaving the blood and entering the epithelial
cell through the facilitated transporter?
a. The amino acid concentration gradient favors net outward movement.
b. The sodium gradient makes amino acids exit into the blood.
c. Facilitated transporters normally work in one direction only, preventing backward
transport..
d. The sodium pump is not active under these conditions so there will be no primary active
transport occurring.
14. Which of the following is NOT one of the five basic types of receptor?
a. G-protein coupled receptors
b. intracellular receptors
c. ligand-gated receptors
d. ras receptors
15. Activator ions are considered essential ion cofactors because
a. they form ionic interactions with biomolecules.
b. they bind loosely in the enzyme active site.
c. the enzyme reaction they help catalyze can not occur in the absence of these ions.
d. they must be transported to establish the ion gradient needed by the cell.
18. Proteoglycans adopt a “bottle-brush structure” because
a. the carbohydrate groups are O-linked to a serine residue on the core protein.
b. the high density of negative charges on the GAGs cause the carbohydrate chains to spread
out.
c. all the double bonds of the chains are in a trans conformation.
d. the high density of positive charges on the amino acids around the glycosidic bonds cause
the carbohydrate chains to spread out.
23. The second messenger of glucagon signaling is
a. Ca2+
b. IP3
c. cAMP
d. cGMP
27. For glycoproteins, the N-linked and O-linked designations refer to
a. the amino acid that the sugar group is bound to.
b. the atom on the sugar that is bound to the amino acid.
c. the atom on the amino acid side chain that the sugar group is bound to.
d. the number of carbohydrate groups bound to the protein.
28. Which enzyme cleaves PIP2 (also called PI-4,5-bisP) to PIP3 and DAG?
a. Phospholipase A1
b. Phospholipase A2
c. Phospholipase C
d. Phospholipase D
30. The insulin receptor substrate (IRS) is
a. phosphorylated by the insulin receptor, which activates it for binding a variety of other
protein targets.
b. binds insulin then activates the insulin receptor’s autophosphorylation activity.
c. an insulin molecule that binds the intracellular face of the receptor.
d. a kinase receptor.