Exam 1

Question 1

2009

The ΔG’º for hydrolysis of ATP is -30.5 kJ/mole. The ΔG’º for hydrolysis of PEP is -61.9 kJ/mole. The ΔG’º for the following reaction is:

PEP + ADP ⇔ Pyruvate + ATP

• -92.4 kJ
• +31.4 kJ
• -31.4 kJ
• +92.4 kJ
• cannot be determined from data provided

Answer 1

-31.4 kJ

( -61.9 - (-30.5) = -31.4 )

Question 2

2009

For A ⇔ B, ΔG’º is negative.

• The rate of reaction of B to A is increased
• The rate of reaction of B to A is decreased
• The rate of reaction of B to A is dependent on the magnitude of ΔG’º
• The rate of reaction is not influenced by the sign of magnitude of ΔG’º
• There is no reaction at all in either direction becase it is at equilibrium

Answer 2

The rate of reaction is not influenced by the sign of magnitude of ΔG’º

Question 3

2009

ln K (K equilibrium constant) is equal to

• RT ΔG’º
• • RT ΔG’º
• ΔG’º/RT
• • ΔG’º/RT
• ΔG’ºT/R

Answer 3

• ΔG’º/RT

( ΔG’º = -RT ln K)

Question 4

2009

ΔG’º (under cellular conditions) for ATP hydrolysis is -50 kJ/mole and 4000 kJ our caloric intake (in 24 hours) is used for synthesis ATP. The amount of ATP formed by a human in 24 hours is (MW ATP ≈ 500)

• ≈ 6g
• 80g
• 0
• -40 Kg
• ATP is only hydrolized

Answer 4

-40 Kg

Question 5

2009

In glycolysis ATP synthesis is catalyzed by

• 6-phosphofructo-1 kinase
• hexokinase
• phosphoglycerate kinase
• glyceraldehyde 3-phosphate dehydrogenase
• none of the above

Answer 5

phosphoglycerate kinase

Question 6

2009

The irreversible reactions of glycolysis include that catalyzed by

• phosphoglycerate kinase
• fructose biphosphate aldolase
• 6-phosphofructo-1-kinase
• glyceraldehyde 3-phosphate dehygrogenase
• phosphoglucose isomerase

Answer 6

6-phosphofructo-1-kinase

Question 7

2009

6-Phosphofructo-1-kinase activity can be decreased by all of the following EXCEPT

• low pH
• AMP
• decreased concentration of fructose 2,6-bisphosphate
• ATP at high concentrations
• citrate

Answer 7

AMP

Question 8

2009

Which of the following supports gluconeogenesis?

• lysine degradation
• leucine degradation
• acetyl CoA + oxaloacetate + H2O ⇔ citrate + CoA
• pyruvate + ATP + HCO3 ⇔ oxaloacetate + ADP + P_i + H⁺
• α-ketoglutarate + aspartate ⇔ glutamate + oxaloacetate

Answer 8

pyruvate + ATP + HCO3 ⇔ oxaloacetate + ADP + P_i + H⁺

Question 9

2009

In the Cori Cyle

• glucose is converted to pyruvate/lactate in anaerobic (i.e. red blood cells) tissues, and this pyruvate/lactate return to the liver, where it is converted to glucose
• nitrogen from alanine must be converted to urea, increasing the amount of energy required to drive the process
• only tissues with aerobic metabolism (i.e. mitochondria and O2) are involved
• the same amount of ATP is used in the liver to synthesize glucose as it is released during glycolysis, leading to no net efect on whole-body energy balance
• a three-carbon compound arising from glycolysis is converted to glucose at the expense of energy from fatty acid oxidation

Answer 9

glucose is converted to pyruvate/lactate in anaerobic (i.e. red blood cells) tissues, and this pyruvate/lactate return to the liver, where it is converted to glucose

Question 10

2009

Gluconeogenic enzymes include all of the following EXCEPT

• phosphoenolpyruvate carboxykinase
• pyruvate carboxylase
• fructose 1,6-bisphosphatase
• phosphogucmutase
• glucose 6-phosphatase

Answer 10

phosphogucmutase

(only in glycolysis)

Question 11

2009

Phospho-dephospho regulation of, 6-phosphofructo-2-kinase, and pyruvate kinase is an important regulatory mechanism in

• skeletal muscle
• liver
• intestine
• erythrocytes
• brain

Answer 11

liver

(where glycolysis occurs)

Question 12

2009

Phosphorylation-dephosphorylation and allosteric activation of enzymes play roles in stimulating glycogen degradation. All of the following result in enzyme activation EXCEPT

• Phosphorylation of Phosphorylase kinase
• Phosphorylation of protein kinase A
• binding of AMP to Phosphorylase b
• Phosphorylation of Phosphorylase
• dePhosphorylation of glycogen synthase

Answer 12

Phosphorylation of protein kinase A

Question 13

2009

Glucose 6-phosphatase, which is deficient in Von Glerke’s disease, is necessary for the production of blood glucose from

• fructose
• galactose
• amino acid carbon chains
• liver glycogen
• all of the above

Answer 13

all of the above

Question 14

2009

Glucose labeled at C-1 is incubated with glycolytic enzymes and necessary cofactors. The pyruvate CH₃COCOO^- that is formed will be labeled at

• C-1
• C-2
• C-3
• All C atoms
• At none of the C atoms

Answer 14

C-3

Question 15

2009

Removal of a glucose residue from glycogen (by phosphorylase) and passing it thorugh glycolysis to 2 pyruvates yields _____ ATP

• 1
• 2
• 3
• 4
• None

Answer 15

3

Question 16

2009

Glucose labeled at C-3 is allowed to undergo fermentation to ethanol CH₃CH₂OH and CO₂. The label will show in

• Ethanol at C-1 only
• Ethanol at C-2 only
• CO₂ only
• Both A and C
• Both B and C

Answer 16

CO₂ only

Question 17

2009

The conversion of 1 mol of fructose 1,6-biphosphate to 2 mol of pyruvate by the glycolytic pathway results in a net formation of:

• 2 mol of NADH and 2 mol of ATP
• 1 mol of NADH and 1 mol of ATP
• 2 mol of NADH and 4 mol of ATP
• 1 mol of NAD⁺ and 2 mol of ATP
• 2 mol of NAD⁺ and 4 mol of ATP

Answer 17

2 mol of NADH and 4 mol of ATP

Question 18

2009

Which of the following statements is true of muscle glycogen phosphorylase?

• It removes glucose residues from the reducing ends of the glycoen chains
• It exists in an active (a) form and an inactive (b) form that is allosterically regulated by AMP
• It degrades glycogen to form glucose 6-phosphate
• It catalyzes phosphorolysis of the α(1→6) bonds at the branch points of glycogen
• It degrades glycogen to glucose

Answer 18

It exists in an active (a) form and an inactive (b) form that is allosterically regulated by AMP

Question 19

2009

Which of these enzymes is a control point, regulated by the cell’s energy supply?

• Phosphofructokinase-1
• Glycogen phosphorylase
• Pyruvate kinase
• All of the above are control points
• None of the above is a control point

Answer 19

All of the above are control points

Question 20

2009

The main function of the pentose phosphate pathway is to

• Supply pentoses and NADPH
• Give the cell an alternate pathway should glycolysis fail
• Supply NADH
• Provide a mechanism for the utilization of the carbon skeletons of excess amino acids
• Supply energy

Answer 20

Supply pentoses and NADPH

Question 21

2009

Which of the following describes fatty acid transport into the mitochondrial matrix?

• It is the rate-limiting step in fatty acid oxidation
• It is regulated by malonyl-CoA
• The cytosolic and matrix pools of CoA are distince and separate
• Once fatty acyl groups have entered the matrix, they are committed to oxidation to acetyl-CoA
• All of the above are true

Answer 21

All of the above are true

Question 22

2009

Fatty acid synthase of mammalian cells

• uses a four-step sequence to lengthen a growing fatty acyl chain by one carbon
• contains ACP, which carries acyl groups attached through thioester linkages
• requires chemical energy in just one form, the reducing power of NADPH
• is activated by glucagon and epinephrine
• is activated by palmitoyl CoA, the principal product of fatty acid synthesis

Answer 22

contains ACP, which carries acyl groups attached through thioester linkages

Question 23

2009

How are fatty acid oxidation and synthesis controlled so that futile cycling (when two opposing reactions/pathways occurring in the same location and at the same time, one forming an energy-rich compound, the other consuming an energy-rich compound) does not occur?

• A - they occur in different cellular compartments
• B - they employ different electron carriers
• C - the product of the first oxidation reaction inhibits the rate-limiting step of biosynthesis
• A and B
• A, B, and C

Answer 23

A and B

Question 24

2009

In mammmalian cells, fatty acid synthesis occurs in the cytosol. The beginning subsrate for this series of reaction is acetyl-CoA, which is formed in the mitochondrial matrix. How does the acetyl-CoA move from matrix to cytosol?

• Acetyl-CoA reacts with oxaloacetate and leaves the matrix as citrate via the citrate transporter
• Acetyl-CoA combines with bicarbonate and is transported out of the matrix as pyruvate
• There is a specific transport protein for acetyl-CoA
• Acetyl-CoA is a nonpolar molecule and can diffuse across all membranse
• Inner and outer mitochondrial membranes are freely permeable to Acetyl-CoA due to the presence of transmembrane pore or channels.

Answer 24

Acetyl-CoA reacts with oxaloacetate and leaves the matrix as citrate via the citrate transporter

Question 25

# 2010 Which of the following BEST describes the relationship between ΔG and the rate of a reaction? * ΔG is linearly proportional to the rate * ΔG is inversely proportional to the rate * if ΔG \> 0, the reaction is spontaneous * if ΔG \< 0, the reaction is at equilibrium * ΔG provides no information about the rate

Answer 25

ΔG provides no information about the rate

Question 26

# 2010 For the reaction A → B, the K_eq is 10⁴. If a reaction mixture originally contains 1 mmol of A and no B, which of the following is true? (R = 8.32 J mol^-1K^-1, T = 300ºK) * At equilibrium, there will be far more A than B * The reaction will definitely proceed toward B at a very high rate * ΔGº' for the reaction will be large and positive * The rate of the reaction may be immeasurably small * ΔGº' will be approximately -23kJ/mole

Answer 26

2010: ΔGº' will be approximately -23kJ/mole 2012, 2015: A. At equilibrium, there will be far more B than A

Question 27

# 2010 In a skeletal muscle cell ΔGº' for hydrolysis of ATP to ADP + P_i is -50 kJ/mole. The approximate ratio of [ATP]/ADP][P_i] found in the cells at 37°C is ΔGº' for ATP hydrolysis -30.5 kJ/mole, R = 8.32 J mol^-1K^-1 * 5000/1 * 4000/1 * 2000/1 * 1000/1 * 200/1

Answer 27

2000/1

Question 28

# 2010 Glucose 1-phosphate is converted to fructose 6-phosphate in two successive reactions? Glucose-1-P → glucose-6-P ΔG'º = -1.7 kcal/mol Glucose-6-P → fructose-6-P ΔG'º = -0.4 kcal/mol What is ΔG'º for the overall reaction? * -2.1 kcal/mol * -1.7 kcal/mol * -1.3 kcal/mol * 1.3 kcal/mol * 2.0 kcal/mol

Answer 28

-2.1 kcal/mol

Question 29

# 2010 The E⁰' of the NAD+/NADH half reaction is -0.32 V. The E⁰' of the oxaloacetate/malate half reaction is -0.175 V. When the concentrations of NAD⁺, NADH, oxaloacetate, and malate are all 10^-5 M, the spontaneous reaction is: * NAD⁺ + oxaloacetate → NADH + H⁺ + malatate * NAD⁺ + NADH + H⁺ → malatate + oxaloacetate * malatate + NADH + H⁺ → oxaloacetate + NADH + H⁺ * malatate + NAD⁺ → oxaloacetate + NADH + H⁺ * oxaloacetate + NADH + H⁺ → malatate + NAD⁺

Answer 29

oxaloacetate + NADH + H⁺ → malatate + NAD⁺

Question 30

# 2010 A person who cannot synthesize liver fructose 1,6-biphosphate would probably not be able to * Synthesize fats when the diet contained excess carbohydrate * Metabolize fructose * Convert fructose 1,6-biphosphate into triose phosphates * Resynthesize glucose from lactate produced during exercise * None of the above are correct

Answer 30

Resynthesize glucose from lactate produced during exercise

Question 31

# 2010 glucose can not be synthesized from which of the following noncarbohydrate precursors? * fumarate * alanine * lactate * palmitic acid * glycerol

Answer 31

palmitic acid

Question 32

# 2010 Starting from a glucose residue in glycogen, how many net ATP molecules will be formed in the glycolysis of the residue to pyruvate? * 1 * 2 * 3 * 4 * 5

Answer 32

3

Question 33

# 2010 If the C-1 carbon of glucose were labeled with ¹⁴C, which of the carbon atoms in pyruvate would be labeled after glycolysis? * The carboxylate carbon * The carbonyl carbon * The methyl carbon * none * all carbon atoms will be labeled

Answer 33

The methyl carbon

Question 34

# 2010 Phosphofructokinase activity is enhanced by which of the following? * Increased ATP concentration * Increased fructose 2, 6-biphosphate concentration * Increased citrate concentration * Decreased AMP concentration * Increased [glucagon] serum

Answer 34

Increased fructose 2, 6-biphosphate concentration

Question 35

# 2010 Place the following steps of the reaction cascade of glycogen metabolism in the proper sequence 1. activation of protein kinase 2. formation of cyclic AMP by adenylate cyclase 3. phosphorylation of phosphorylase kinase 4. hormone binding to target cell receptors 5. phosporylaiton of glycogen synthase a and phosphorylase b * 1,2,3,4,5 * 2,4,1,5,2 * 4,2,1,3,5 * 5,4,3,2,1 * 2,1,4,5,3

Answer 35

4,2,1,3,5

Question 36

# 2010 Inorganic fluoride inhibits enolase. In an anaerobic system that is metabolizing glucose as a substrate, which of the following compounds would you expect to increase in concentration following the addition of fluoride? * glucose * phosphoenolpyruvate * glyoxylate * 3-phosphoglycerate * pyruvate

Answer 36

3-phosphoglycerate

Question 37

# 2010 The conversion of one mole of glucose-6-phosphate to two moles of lactate in glycolysis is accompanied by a net gain of: * 3 moles of ATP * 2 moles of ATP * 1 mole of ATP * 1 mole of NADH * 2 moles each of ATP and NADH

Answer 37

3 moles of ATP

Question 38

# 2010 In glycolysis, fructose 1,6-biphosphate is converted to two products with a standard free-energy change (ΔG°') of 23.8 kJ/mol. Under what conditions encountered in a normal cell will the free-energy change (ΔG°') be negative, enabling the reaction to proceed spontaneously to the right? * 2010 / 2015: Under standard conditions, enough energy is released to drive the reaction to the right * 2010 / 2015: The reaction will not go to the right spontaneously under any conditions because the ΔG°' is positive * 2010 / 2015: The driving force of this reaction is supplied by a coupled exergonic reaction, the hydrolysis of ATP * 2015: When there is a high concentration of products relative to the concentration of fructose 1,6- bisphosphate. * 2010: The reaction may proceed given appropriate concentrations of fructose-1,6-bisphosphate and the products * 2015: When there is a high concentration of fructose 1,6-bisphosphate relative to the concentration of products * 2010 / 2015: none of the above conditions is sufficient

Answer 38

* 2010: The reaction may proceed given appropriate concentrations of fructose-1,6-bisphosphate and the products * 2015: When there is a high concentration of fructose 1,6-bisphosphate relative to the concentration of products

Question 39

# 2010 If glucose labeled with ¹⁴C in C-3 were fed to yeast carrying out of the ethanol fermentation, where would the ¹⁴C label be in the products? * C-1 (methyl group) of ethanol * C-1 of ethanol only * CO₂ only * C-2 of ethanol and CO₂ * C-1 of ethanol and CO₂

Answer 39

CO₂ only

Question 40

# 2010 Glyceraldehyde-3-phosphate labeled with ¹⁴C in C-1 (the carbonyl carbon) is mixed wiht unlabeled dihydroxyacetone phosphate and the enzymes triose phosphate isomerase and aldolase. After a period of incubation, fructose-1,6-bisphosphate is isolated from this system. It will be labeled with ¹⁴C in: * C-1 only * C-3 only * C-1 and C-3 * C-1 and C-6 * C-3 and C-4

Answer 40

C-3 and C-4

Question 41

# 2010 Galactosemia is a genetic error of metabolism principally associated with * excessive ingestion of galactose * inability to digest lactose * deficiency of galactokinase * deficiency of UDP-glucose: galactose 1-phosphate uridylyltransferase * deficiency of UDP-glucose epimerase

Answer 41

deficiency of UDP-glucose: galactose 1-phosphate uridylyltransferase

Question 42

# 2010 When blood glucose levels are low, glucagon is secreted. Which of the following are the effects of increased glucagon levels on glycolysis and related reactions in the liver? 1. Phosphorylation of phosphofructokinase 2 occurs 2. Dephosphorylation of phosphofructokinase 2/fructose bisphosphatase 2 occurs 3. phosphofructokinase-1 is activated 4. phosphofructokinase-1 is inhibited 5. glycolysis is accelarated 6. glycolysis is slowed down * 1,3,6 * 2,3 * 1,4,6 * 2,5 * 2,3,5

Answer 42

1,4,6

Question 43

# 2010 The oxidation of 3 moles of glucose by the pentose phosphate pathway may result in the production of * 3 moles of pentose, 4 moles of NADPH, and 3 moles of CO₂ * 2 moles of pentose, 8 moles of CO₂, and 4 moles of NADPH * 3 moles of CO_2, 6 moles of NADPH, and 3 moles of pentose * 6 moles of CO_2, 6 moles of NADPH, and 4 moles of triose * 18 moles of CO_2, 18 moles of NADPH

Answer 43

3 moles of CO_2, 6 moles of NADPH, and 3 moles of pentose

Question 44

# 2010 Which of the following is true of the control of gluconeogenesis? * glucagon stimulates adenylyl cyclase, causing the formation of cAMP * Cyclic AMP stimulates the phosphorylation and thus increases the activity of FBPase-2 * FBPase-2 activity lowers the level of fructose 2,6-bisphosphate, thus increasing the rate of gluconeogenesis * It is reciprocally linked to the control of glycolysis * all of the above are true

Answer 44

all of the above are true

Question 45

# 2010 Which of the following has the (immediate) effect of increasing the rate of glycogen breakdown? * A- increased concentration of cAMP * B- increase in the [AMP]/[ATP] ratio * C- increased secretion of glucagon * A and C * A, B, and C

Answer 45

A, B, and C

Question 46

# 2010 Which of the following correctly matches the glycolytic reaction with the gluconeogenic enzyme used in the corresponding bypass reaction? * Glucose → glucose 6-phosphate; glucose 6-phosphatase * Fructose 6-phosphate → fructose 1,6-bisphosphate; phosphofructokinase-2 * Fructose 1,6-bisphosphate → dihydroxyacetone phosphate + glyceraldehyde 3-phosphate; glyceraldehyde 3-phosphate dehydrogenase * 2-Phosphoglycerate → phosphoenolpyruvate; phosphoglycerate kinase * Phosphoenolpyruvate → pyruvate; pyruvate kinase

Answer 46

Glucose → glucose 6-phosphate; glucose 6-phosphatase

Question 47

# 2010 Transport of fatty acids from the cytoplasm to the mitochondrial matrix requires: * ATP, coenzyme A, and hexokinase * ATP, carnitine and coenzyme A * carnitine, coenzyme A, and hexokinase * ATP, carnitine, and pyruvate dehydrogenase * ATP, coenzyme A, and pyruvate dehydrogenase

Answer 47

ATP, carnitine and coenzyme A

Question 48

# 2010 Lipoprotein lipase acts in * intracellelar lipid breakdown of lipoproteins * intestinal uptake of dietary fat * lipoprotein breakdown to supply needed amino acids * hydrolysis of triacylglycerols of plasma lipoproteins to supply fatty acids to various tissues * none of the above

Answer 48

hydrolysis of triacylglycerols of plasma lipoproteins to supply fatty acids to various tissues

Question 49

Fatty acids are activated to acyl-CoAs and the acyl group is further transferred to carnitine because * acyl-CoAs easily cross the mitochondrial membrane, but the fatty acids themselves will not * fatty acids cannot be oxidized by FAD unless they are in the acyl-carnitine form * carnitine is required to oxidize NAD⁺ to NADH * acyl-carnitines readily cross the mitochondrial inner membrane, but acyl-COAs do not * None of the above is true

Answer 49

acyl-carnitines readily cross the mitochondrial inner membrane, but acyl-COAs do not

Question 50

# 2010 Which of the following is (are) true of the oxidation of 1 mol of palmitate (a 16-carbon saturated fatty acid; 16:0) by the β-oxidation pathway, beginning with the free fatty acid in the cytoplasm? 1. Activation of the free fatty acid requires the equivalent of two ATP 2. Inorganic pyrophosphate (PP_i) is produced 3. Carnitine functions as an electron acceptor 4. 8 mol of FADH₂ are formed 5. 8 mol of acetyl-CoA are formed 6. there is no direct involvement of NAD⁺ * 1, 2, 6 * 1, 3, 5 * 1 and 5 only * 5 only * 1, 2, and 5

Answer 50

1, 2, and 5

Question 51

# 2010 Place the following steps in lipid oxidation in their proper sequence 1. a - Thiolysis 2. b - Reaction of fatty acyl-ClA with carnitine 3. c - Oxidation requiring NAD⁺ 4. d - Hydrolysis of triacylglycerol by lipase 5. e - Activation of fatty acid by joining to CoA 6. f - Hydration * 5, 4, 3, 2, 1, 6 * 4, 5, 2, 3, 4, 1 * 4, 2, 5, 3, 6, 1 * 1, 4, 5, 2, 6, 1 * 5, 4, 2, 3, 1, 6

Answer 51

4, 5, 2, 3, 4, 1 d, e, b, c, f, a * Hydrolysis of triacylglycerol by lipase * Activation of fatty acid by joining to CoA * Reaction of fatty acyl-ClA with carnitine * Oxidation requiring NAD⁺ * Hydrolysis of triacylglycerol by lipase * Thiolysis

Question 52

# 2012 When the serum glucose concentrations falls below the normal level, which of the following will occur? * A. Glycolysis in red blood cells and nerve cell slows down * B. Glycolysis in these cells continues normally * C. Skeletal muscle contraction stops so as to save glucose * D. Glycolysis in liver is increased * E. None of the above

Answer 52

B. Glycolysis in these cells continues normally

Question 53

# 2012 Biological oxidation-reduction reactions always involve: * A. direct participation of oxygen. * B. formation of water. * C. mitochondria. * D. transfer of electron(s) * E. transfer of hydrogens

Answer 53

D. transfer of electron(s)

Question 54

# 2012 Which of the following statements concerning signal transduction by the insulin receptor is not correct? * A. Activation of the receptor protein kinase activity results in the activation of additional protein kinases. * B. Binding of insulin to the receptor activates a protein kinase. * C. Binding of insulin to the receptor results in a change in its quaternary structure. * D. The receptor protein kinase activity is specific for tyrosine residues on the substrate proteins. * E. The substrates of the receptor protein kinase activity are mainly proteins that regulate transcription

Answer 54

E. The substrates of the receptor protein kinase activity are mainly proteins that regulate transcription

Question 55

# 2012 Which of the following does not involve cyclic AMP? * A. Regulation of glycogen synthesis and breakdown * B. Regulation of glycolysis * D. Signaling by epinephrine * C. Signaling by acetylcholine * E. Signaling by glucagon

Answer 55

C. Signaling by acetylcholine

Question 56

# 2012 Hormone-activated phospholipase C can convert phosphatidylinositol 4,5-bisphosphate to: * A. diacylglycerol + inositol triphosphate. * B. diacylglycerol + inositol+ phosphate. * C. glycerol + inositol + phosphate. * D. glycerol + phosphoserine. * E. phosphatidyl glycerol + inositol + phosphate.

Answer 56

A. diacylglycerol + inositol triphosphate.

Question 57

# 2012 Gluconeogenesis occurs during intense exercise. This seems counter-intuitive. * A. This is not true; two opposing pathways would result in net hydrolysis of ATP * B. Intense exercise consumes fatty acids only, * C. Skeletal muscle converts glucose residues to pyruvate and lactate. Rising level of lactate causes lactate to pass from muscle to blood to liver where the lactate can be converted (by gluconeogenesis) to glucose. * D. During exercise, glucose is transported from blood into muscle. When serum glucose has been depleted, liver forms glucose by gluconeogenesis and glycogenolysis. * E. Insulin activates the Glut 4 and glucose transport into muscle increases.

Answer 57

C. Skeletal muscle converts glucose residues to pyruvate and lactate. Rising level of lactate causes lactate to pass from muscle to blood to liver where the lactate can be converted (by gluconeogenesis) to glucose.

Question 58

# 2012 In the coordinated control of glycolysis and gluconeogenesis in liver * A. Citrate inhibits PFK and stimulates F-1 ,6-Bpase. * B. Fructose 2,6-bisphosphate stimulates F-1,6-Bpase and inhibits PFK. * C. Acetyl CoA inhibits PFK and stimulates F-1,6-Bpase. * D. AMP inhibits PFK and stimulates F-1,6-Bpase. * E. NADPH inhibits PFK and stimulates F-1,6-Bpase.

Answer 58

A. Citrate inhibits PFK and stimulates F-1 ,6-Bpase.

Question 59

Avidin, a 70-kd protein in egg white has a high affinity for biotin. In fact, it is a highly specific inhibitor of biotin enzymes. Which of the following conversions would be blocked by the addition of avidin to a cell homogenate? * A. Glucose → Pyruvate * B. Pyruvate → Glucose * C. Oxaloacetate → Glucose * D. Malate →oxaloacetate * E. Glyceraldehyde-3-P → Fructo 1 ,6-Bis P

Answer 59

B. Pyruvate → Glucose

Question 60

# 2012 Glucose, labeled with ¹⁴C in different carbon atoms, is added to a crude extract of a tissue rich in the enzymes of the pentose phosphate pathway. The most rapid production of ¹⁴CO2 will occur when the glucose is labeled in: * A. C-1 * B. C-3 * C. C-4 * D. C-5 * E. C-6

Answer 60

A. C-1

Question 61

# 2012 Glucose labeled with ¹⁴C at C-6 is added to a solution containing the enzymes and cofactors of the oxidative branch of the pentose phosphate pathway. The radioactive label will be found in D-ribulose-5P at * A. C-1 * B. C-2 * C. C-3 * D. C-4 * E. C-5

Answer 61

E. C-5

Question 62

# 2012 When blood glucagon rises, which of the following hepatic enzyme activities FALLS? * A. adenyl cyclase * B. protein kinase A * C. 6-phosphofructo-2-kinase * D. fructose 1 ,6-bisphosphatase * E. hexokinase

Answer 62

E. hexokinase

Question 63

# 2012 Malignant hyperthermia is a genetic abnormality in which exposure to certain agents, especially the widely used general anesthetic halothane, produces a dramatic rise in body temperature, acidosis, hyperkalemia, and muscle rigidity. Death is rapid if the condition is untreated and may occur the first time a susceptible person is anesthetized. The defect causes an inappropriate release of Ca²⁺ from the sarcoplasmic reticulum of muscle. Many heat producing processes are stimulated in an uncontrolled fashion by the release of Ca²⁺, including glycolysis and glycogenolysis. Ca2+ increases glycogenolysis by: * A. activating phosphorylase kinase b, even in the absence of cAMP * B. binding to phosphorylase b. * C. activating phosphoprotein phosphatase. * D. inhibiting phosphoprotein phosphatase. E. protecting cAMP from degradation.

Answer 63

A. activating phosphorylase kinase b, even in the absence of cAMP

Question 64

# 2012 Malignant hyperthermia is a genetic abnormality in which exposure to certain agents, especially the widely used general anesthetic halothane, produces a dramatic rise in body temperature, acidosis, hyperkalemia, and muscle rigidity. Death is rapid if the condition is untreated and may occur the first time a susceptible person is anesthetized. The defect causes an inappropriate release of Ca²⁺ from the sarcoplasmic reticulum of muscle. Many heat producing processes are stimulated in an uncontrolled fashion by the release of Ca²⁺, including glycolysis and glycogenolysis. Phosphorylation-dephosphorylation and allosteric activation of enzymes play roles in stimulating glycogen degradation. All of the following result in enzyme activation EXCEPT: * A. phosphorylation of phosphorylase kinase. * B. binding of AMP to phosphorylase b. * C. phosphorylation of phosphorylase * D. phosphorylation of protein kinase A. * E. dephosphorylation of glycogen synthase.

Answer 64

D. phosphorylation of protein kinase A.

Question 65

# 2012 Malignant hyperthermia is a genetic abnormality in which exposure to certain agents, especially the widely used general anesthetic halothane, produces a dramatic rise in body temperature, acidosis, hyperkalemia, and muscle rigidity. Death is rapid if the condition is untreated and may occur the first time a susceptible person is anesthetized. The defect causes an inappropriate release of Ca²⁺ from the sarcoplasmic reticulum of muscle. Many heat producing processes are stimulated in an uncontrolled fashion by the release of Ca²⁺, including glycolysis and glycogenolysis. Which one of the following is not a characteristic of phosphoprotein phosphorylase-1 (PP1)? * A. PP1 can be phosphorylated by protein kinase A (PKA). * B. PP1 can dephosphorylate glycogen phosphorylase, glycogen synthase, and phosphorylase kinase. * C. PP1 is allosterically activated by glucose-6-phosphate. * D. PP1 is inhibited by activated glycogen phosphorylase * E. PP1 is phosphorylated by glycogen synthase kinase-3 (GSK3).

Answer 65

E. PP1 is phosphorylated by glycogen synthase kinase-3 (GSK3).

Question 66

# 2012 The role of hormone-sensitive triacylglycerol lipase is to: * A. hydrolyze lipids stored in the liver. * B. hydrolyze membrane phospholipids in hormone-producing cells. * C. hydrolyze triacylglycerols stored in adipose tissue. * D. synthesize lipids in adipose tissue. * E. synthesize triacylglycerols in the liver.

Answer 66

C. hydrolyze triacylglycerols stored in adipose tissue.

Question 67

# 2012 Which of the following statements concerning the β oxidation of fatty acids is true? * A. About 1,200 ATP molecules are ultimately produced per 20-carbon fatty acid oxidized. * B. One FADH2 and two NADH are produced for each acetyl-CoA. * C. The free fatty acid must be carboxylated in the β position by a biotin-dependent reaction before the process of β oxidation commences. * D. The free fatty acid must be converted to a thioester before the process of β oxidation commences. * E. Two NADH are produced for each acetyl-CoA.

Answer 67

D. The free fatty acid must be converted to a thioester before the process of β oxidation commences.

Question 68

# 2012 The balanced equation for the degradation of CH₃(CH₂)₁₀COOH via the β-oxidation pathway is: * A. CH₃(CH₂)₁₀COOH + 5FAD + 5NAD⁺ + 6CoA—SH + 5H₂O + ATP → 6 Acetyl-CoA + 5FADH₂ + 5NADH + 5H⁺ + AMP + PP_i * B. CH₃(CH₂)₁₀COOH + 5FAD + 5NAD⁺ + 6CoA—SH + 5H₂O → 6 Acetyl-CoA + 5FADH₂ + 5NADH + 5H⁺ * C. CH₃(CH₂)₁₀COOH + 6FAD + 6NAD⁺ + 6CoA—SH + 6H₂O + ATP → 6 Acetyl-CoA + 6FADH₂ + 6NADH + 6H⁺ + AMP + PP_i * D. CH₃(CH₂)₁₀COOH + 6FAD + 6NAD⁺ + 6CoA—SH + 6H₂O → 6 Acetyl-CoA + 6FADH₂ + 6NADH + 6H⁺

Answer 68

A. CH₃(CH₂)₁₀COOH + 5FAD + 5NAD⁺ + 6CoA—SH + 5H₂O + ATP → 6 Acetyl-CoA + 5FADH₂ + 5NADH + 5H⁺ + AMP + PP_i

Question 69

# 2013 Restriction enzymes * A. used in Northern analysis * B. used for protein processing * C. recognize palindromic sequences of DNA * D. recognize palindromic sequences of RNA * E. cut randomly in the genome

Answer 69

C. recognize palindromic sequences of DNA

Question 70

# 2013 PCR: * A. stands for polymer chain response * B. can only use DNA as a template * C. can be used to amplify RNA sequences * D. requires gel electrophoresis for detection * E. is used in western analysis

Answer 70

B. can only use DNA as a template

Question 71

# 2013 mRNA: * A. is the most abundant RNA in the cell * B. can be separated from other RNA species by polyA isolation * C. can be analyzed by Southern analysis * D. is not really important * E. can be used as a template for PCR

Answer 71

B. can be separated from other RNA species by polyA isolation

Question 72

# 2013 Generation of a knockout animal involves: * A. homologous recombination * B. random insertion of exogenous DNA * C. targeted insertion of exogenous RNA * D. use of siRNA to eliminate DNA expression * E. competent rat species

Answer 72

A. homologous recombination

Question 73

# 2013 Which of the following is a true statement about DNA: * A. All DNA in a eukaryotic organism is in heterochromatin form unless activated * B. Prokaryotic DNA is capped by telomere sequences * C. 1.5% of eukaryotic DNA is considered genes * D. All DNA in eukaryotic organisms is in euchromatin form unless activated * E. 1.5% of all eukaryotic DNA is coding.

Answer 73

E. 1.5% of all eukaryotic DNA is coding.

Question 74

# 2013 fMet : * A. is the last amino acid added to the polypeptide chain * B. is necessary for the elongation step of translation * C. only exists in the tRNA structure * D. has a specific tRNA separate from Met. * E. has a different codon than Met

Answer 74

D. has a specific tRNA separate from Met

Question 75

# 2013 Eukaryotic translation: * A. is exactly the same as prokaryotic transcription * B. requires a multiprotein complex that links the transcribed RNA to the translational machinery via the 5’ cap and poly A tail. * C. does not use AUG as the start codon * D. requires a shine-delgardo sequence to start translation. * E. is dependant on the sigma factor

Answer 75

B. requires a multiprotein complex that links the transcribed RNA to the translational machinery via the 5’ cap and poly A tail.

Question 76

# 2013 RNA polymerase II is distinct in that it * A. Is only used to generate tRNAs * B. Is only found in eukaryotic organisms * C. Is effective on a variety of different promoters * D. Is used to make primers for DNA replication * E. Makes Okazaki fragments.

Answer 76

C. Is effective on a variety of different promoters

Question 77

# 2013 In prokaryotes, RNA polymerase finds the start of transcription by: * A. Specific sequences in the promoter region * B. Identification of the cap structure * C. Sliding along the DNA and looking for unwound segments * D. Signaling the histone molecules to disconnect from the wound DNA * E. Sliding along the DNA to find a specific stem-loop structure

Answer 77

A. Specific sequences in the promoter region

Question 78

# 2013 Which of the following statements is FALSE: * A. Many amino acids can be encoded by several codons * B. Mitochondria have a slightly different “code” than that of the eukaryotic organism * C. The wobble hypothesis comes from the finding that there is greater freedom in pairing in the first position of the codon * D. Aminoacyl-tRNA synthetases function to add the amino acid onto the tRNA * E. Aminoacyl-tRNA synthetases can proofread

Answer 78

C. The wobble hypothesis comes from the finding that there is greater freedom in pairing in the first position of the codon

Question 79

# 2013 Splicing: * A. can occur through ATP-dependant and –independent mechanism. * B. Is critical to remove exons so introns can be joined together * C. Depends on a 5’ pG and an internal branch site * D. Generates a holiday junction * E. A & C 2013 Exam options * A. requires ATP * B. Is critical to remove introns so exons can be joined together * C. Depends on a 5’ pG and an internal branch site * D. A & C * E. B & C

Answer 79

E. A & C * can occur through ATP-dependant and –independent mechanism. * Depends on a 5’ pG and an internal branch site 2013 Exam Answers * B. Is critical to remove introns so exons can be joined together * C. Depends on a 5’ pG and an internal branch site

Question 80

# 2013 Histone acetylation plays a critical role in: * A. DNA replication * B. RNA structure * C. Activation of transcription * D. The Lac operon * E. Proofreading the degenerate code

Answer 80

C. Activation of transcription

Question 81

# 2013 Protein translation in the endoplasmic reticulum: * A. Only occurs in prokaryotes * B. Requires a signal sequence * C. Is necessary for all proteins in the cell * D. A & C * E. B & C

Answer 81

B. Requires a signal sequence

Question 82

# 2013 Facilitated diffusion through a biological membrane is: * A. driven by a difference of solute concentration. * B. driven by ATP. * C. Endergonic. * D. generally irreversible * E. not specific with respect to the substrate

Answer 82

A. driven by a difference of solute concentration.

Question 83

# 2013 The acetylcholine receptor is a * A. Steroid receptor. * B. a membrane protein that permits a ligand to pass through the membrane only when opened by the appropriate ion. * C. a membrane protein that permits an ion to pass through the membrane only when opened by the appropriate ligand. * D. a molecule that binds to the membrane thereby allowing ions to pass through. * E. always requires a second ligand to close the channel once it is opened.

Answer 83

C. a membrane protein that permits an ion to pass through the membrane only when opened by the appropriate ligand.

Question 84

# 2013 The figure above is a hydropathy plot. What does this predict about bacteriorhodopsin? * A. It is very water soluble * B. It will bind to specific sequences in DNA as a transcription factor * C. It is an integral membrane protein with seven membrane spanning domains. * D. It is an integral membrane protein with five membrane spanning domains. * E. It will fold into a beta-pleated sheet.

Answer 84

C. It is an integral membrane protein with seven membrane spanning domains.

Question 85

# 2013 When a computer is looking for a potential open reading frame (ORF) it: * A. finds ATG and stop codon. * B. scans for translatable length higher than set threshold. * C. repeats 3 times. * D. A & B. * E. A, B & C

Answer 85

D. A & B.

Question 86

# 2013 Which one of the following is not involved in classical steroid hormone action? * A. Cell surface receptors * B. Hormone-receptor complexes * C. Specific DNA sequences * D. Transcription activation and repression * E. Zinc fingers

Answer 86

A. Cell surface receptors

Question 87

# 2013 The signal sequences that direct proteins to the nucleus are: * A. always at the amino terminus of the targeted protein. * B. cleaved after the protein arrives in the nucleus. * C. glycosyl moieties containing mannose 6-phosphate residues. * D. not located at the ends of the peptide, but in its interior.

Answer 87

D. not located at the ends of the peptide, but in its interior.

Question 88

# 2013 What is the name of the above lipid: * A. 18:1 (Δ9) cis-9-octodecenoic acid * B. 18:1 (Δ10) cis-10-octodecenoic acid * C. 17:1 (Δ9) cis-9-octodecenoic acid * D. 17:1 (Δ10) cis-10-octodecenoic acid

Answer 88

A. 18:1 (Δ9) cis-9-octodecenoic acid

Question 89

# 2013 In comparison to 20:4 (Δ5,8,11, 14), the above lipid would: * A. Have a higher melting temperature * B. Have a lower melting temperature * C. more likely to be incorporated into membranes * D. A & C * E. A & B

Answer 89

B. Have a lower melting temperature

Question 90

# 2013 In the picture to the left, the bottom of the gel is toward the cathode, and the top is toward the anode. Which of the below statements are true. * A. Linking number is larger at the bottom of the gel, than at the top. * B. Linking number is related to the number of bands in the lane. * C. The DNA at the top of the gel is supercoiled * D. The DNA at the bottom of the gel is supercoiled. * E. The second lane is RNA.

Answer 90

D. The DNA at the bottom of the gel is supercoiled.

Question 91

# 2013 Histone H1 is different from the other histones in that: * A. It is associated with packaging RNA. * B. It is found primarily in prokaryotes. * C. It is not part of the histone core particle, but seals the nucleosome at the edge of the linker DNA. * D. It is found only in eukaryotes. * E. It is a pseudogene.

Answer 91

C. It is not part of the histone core particle, but seals the nucleosome at the edge of the linker DNA.

Question 92

# 2013 Single strand repair: * A. Occurs when there is a mismatch base in the DNA strand causing a distortion. * B. Requires a RNA intermediate * C. Requires ligase * D. A & C * E. A & B

Answer 92

D. A & C

Question 93

# 2013 REC A is a protein that: * A. Is an ATPase * B. Is important for DNA recombination * C. Is critical for binding to histone H2 * D. A & C * E. A & B

Answer 93

E. A & B

Question 94

# 2013 Given p(A)=0.5, p(C)=0.1, p(G)=0.2, and p(T)=0.2. Which string is most likely NON-RANDOM? * A. AACTG * B. AAAAA * C. ATATA * D. CCACG * E. CCCCC

Answer 94

E. CCCCC

Question 95

# 2013 Genome assembly REQUIRES * A. Multiple runs to generate matching of overlapping read sequences * B. Use of Sanger sequencing * C. Use of pyrosequencing or Sanger sequencing * D. Use of shotgun sequencing * E. An understanding of intron exon boundaries

Answer 95

A. Multiple runs to generate matching of overlapping read sequences

Question 96

# 2013 What do we lose when we view DNA as a string? * A. Any useful information * B. Histone binding and DNA accessibility information * C. the ability to identify ORFs * D. splicing information

Answer 96

B. Histone binding and DNA accessibility information

Question 97

# 2013 What is the (3’-5’) DNA sequence encoded in this Sanger sequencing gel? * A. …ATGGTGACA… * B. …TACCACTGT… * C. …ACAGTGGTA… * D. …TGTCACCAT… * E. None of the above

Answer 97

B. …TACCACTGT…

Question 98

# 2013 Pyrosequencing differs from Sanger sequencing in that: * A. It does not require a primer * B. It generates longer reads (2,900 bp versus 400- 900 bp) * C. It does not result in chain termination * D. A & C * E. A & B

Answer 98

C. It does not result in chain termination

Question 99

# 2014 A signaling receptor such as is shown below would be expected to * A. bind a broad range of hormones * B. be unresponsive without an auxiliary signal * C. bind only one kind signal molecule or only signals containing particular chemical groups * D. generate a response without binding a signal molecule * E. none of the above

Answer 99

C. bind only one kind signal molecule or only signals containing particular chemical groups

Question 100

# 2014 As part of the β-adrenergic receptor system the protein Gscx dissociates from the receptor complex upon epinephrine binding and moves to adenylyl cyclase, exchanging a bound GDP for GTP in the process. This activates adenylyl cyclase, which produces c-AMP. After some time Gscx ceases to activate, and the production of c-AMP stops. Why? * A. Cellular proteases attack Gscx, inactivating it. * B. When the concentration of c-AMP rises, it binds to Gscx, thereby inhibiting it, an example of feedback inhibition. * C. c-AMP stimulates phosphorylation of the receptor system, causing epinephrine to dissociate and ending the response * D. Gscx slowly hydrolyzes its GTP, thereby losing its ability to bind to adenylyl cyclase, so it returns to become part of the receptor complex. * E. none of the above

Answer 100

D. Gscx slowly hydrolyzes its GTP, thereby losing its ability to bind to adenylyl cyclase, so it returns to become part of the receptor complex.

Question 101

# 2014 Cyclic AMP has what effect on protein kinase A? * A. On binding to the catalytic subunits, it causes them to dissociate from the regulatory subunits. The resulting change in catalytic subunit conformation activates their ability to phosphorylate other proteins. * B. On binding to the regulatory subunits, it causes the catalytic subunits to dissociate from the regulatory subunits. This makes the substrate binding cleft in the catalytic subunits available to phosphorylate other proteins. * C. It stimulates hydrolysis of the regulatory subunits. * D. It inhibits hydrolysis of the catalytic subunits * E. c-AMP has no effect at all on protein kinase A.

Answer 101

B. On binding to the regulatory subunits, it causes the catalytic subunits to dissociate from the regulatory subunits. This makes the substrate binding cleft in the catalytic subunits available to phosphorylate other proteins.

Question 102

# 2014 What of the following is/are true of calmodulin? * A. It acts as a “sensor” for free calcium ion. * B. When its Ca++ binding sites are occupied, it undergoes a conformational change leading it to bind to other proteins. * C. On binding to other proteins it activates their phosphorylating function. * D. Its calcium binding sites have the conformation of an “EF hand.” * E. All of the above are true.

Answer 102

E. All of the above are true.

Question 103

# 2014 10. Which of the steps in the insulin cascade shown here would be expected to amplify directly the insulin binding signal? * A. phosphorylation of IRS-1 * B. dissociation of Grb2 from SOS * C. phosphorylation of MEK * D. the catalytic activity of Raf-1 once Raf-1 has been activated * E. more than one of the above

Answer 103

E. more than one of the above

Question 104

# 2014 11. In bacterial chemotaxis, attractant binding leads to phosphorylation of an asp on component 2, which binds to the flagellar motor thereby causing counterclockwise rotation and thus a “run.” Tumbling, caused by clockwise motor rotation, ends a run, allowing change of direction. What must happen for the transition from run to tumble to occur? * A. Component 2 must dissociate from the motor. * B. A phosphatase must act on component 2. * C. The attractant must be consumed. * D. A timer must exist to ensure that runs away from the attractant are shorter than those toward it. * E. More than one of the above.

Answer 104

E. More than one of the above.

Question 105

# 2014 The aldolase reaction in glycolysis * A. converts fructose-6-phosphate to fructose-1,6-bisphosphate. * B. converts dihydroxyacetone phosphate to glyceraldehyde-3 phosphate. * C. converts pyruvate to lactate in active muscle. * D. glyceraldehydes-3-phosphate to 1,3-bisphosphoglyceric acid. * E. none of the above

Answer 105

E. none of the above

Question 106

# 2014 How many carbon dioxide molecules are produced in the glycolytic conversion of glucose to pyruvate? * A. none * B. one * C. two * D. four * E. more than 4

Answer 106

A. none

Question 107

# 2014 Why is glucose-6-phosphate isomerized to fructose-6-phosphate in glycolysis? * A. The fructose-6-phosphate is more resistant to spontaneous hydrolysis, which would cause loss of the phosphate. * B. It allows phosphorylation at C1 to occur so that when the six carbon sugar is split into two three carbon pieces, each will have a phosphate on it. * C. The fructose-6-phosphate is more likely to be in the open chain form, which makes it a good substrate for enzymes later in the path. * D. The fructose-6-phosphate is less likely to be in the open chain form, which makes it a good substrate for enzymes later in the path. * E. none of the above

Answer 107

B. It allows phosphorylation at C1 to occur so that when the six carbon sugar is split into two three carbon pieces, each will have a phosphate on it.

Question 108

# 2014 What main purpose is served by the anerobic conversion of pyruvate to lactate? * A. to provide a lactate reserve for conversion back to pyruvate * B. to prevent pyruvate from forming acetyl CoA which would enter the TCA cycle * C. to promote gluconeogenesis * D. to regenerate NAD+ from NADH, without which glycolysis couldn’t continue * E. none of the above

Answer 108

D. to regenerate NAD+ from NADH, without which glycolysis couldn’t continue

Question 109

# 2014 The enzymes of glycolysis (in no particular order) are * 1) enolase * 2) phosphofructokinase-1 * 3) phosphoglycerate kinase * 4) phosphohexose isomerase * 5) pyruvate kinase * 6) hexokinase * 7) aldolase * 8) glyceraldehyde 3-phosphate dehydrogenase * 9) triose phosphate isomerase * 10) phosphoglycerate mutase Which of the following sets enzymes do not play a role in gluconeogenesis, the back reaction being catalyzed by other enzymes not listed here? * A. 2, 5, 6 * B. 1, 3, 5 * C. 3, 4, 7 * D. 7, 9, * 10 E. none of the above

Answer 109

A. 2, 5, 6

Question 110

# 2014 Why, if all the intermediates between glucose and pyruvate are the same for glycolysis and gluconeogenesis, are different enzymes used for some of the steps in each direction? * A. so that both routes can operate at the same time * B. so that separate controls for each path can ensure that only one path operates at any given time * C. to reduce the high energy phosphate consumption of gluconeogenesis so that the ATP from glycolysis is not wasted * D. to preserve reducing power by using less NADH in gluconeogenesis * E. all of the above

Answer 110

B. so that separate controls for each path can ensure that only one path operates at any given time

Question 111

# 2014 α-keto acids can be converted by transamination to amino acids for protein synthesis, and when energy is needed, proteins can be broken down and amino acids can be transaminated to α-keto acids so their carbon skeletons can be oxidized. Taking glycolysis and the TCA cycle as a whole, how many of the intermediates can be transaminated directly to amino acids? * A. none * B. one * C. two * D. three * E. more than three

Answer 111

D. three

Question 112

# 2014 Although molecular oxygen does not participate directly in any of the reactions in the citric acid cycle, the cycle only operates when oxygen is present. This is because O2: * A. is necessary as an activator for several enzymatic dehydrogenations (oxygenations) in the cycle. * B. is necessary for producing water, which is crucial for all cellular processes. * C. accepts electrons from the electron transfer chain, allowing reoxidation of NADH to NAD+ . * D. removes toxic by-products of the citric acid cycle. * E. has all of the above functions.

Answer 112

C. accepts electrons from the electron transfer chain, allowing reoxidation of NADH to NAD+ .

Question 113

# 2014 Which one of the following statements about gluconeogenesis is false? * A. For starting materials, it can use carbon skeletons derived from certain amino acids. * B. It consists entirely of the reactions of glycolysis, operating in the reverse direction. * C. It employs the enzyme glucose 6-phosphatase. * D. It is one of the ways that mammals maintain normal blood glucose levels between meals. * E. It requires metabolic energy (ATP or GTP).

Answer 113

B. It consists entirely of the reactions of glycolysis, operating in the reverse direction.

Question 114

# 2014 A crude tissue preparation capable of carrying out the reactions of the citric acid cycle given acetyl-CoA uniformly labeled in both carbons with ¹⁴C. After one turn of the cycle, oxaloacetate would have ¹⁴C in: * A. all four carbon atoms. * B. no pattern that is predictable from the information provided. * C. none of its carbon atoms. * D. the keto carbon and one of the carboxyl carbons. * E. the two carboxyl carbons.

Answer 114

A. all four carbon atoms.

Question 115

# 2014 In the oxidative decarboxylation of pyruvate by the pyruvate dehydrogenase complex to yield acetyl-CoA, the first step is removal of CO₂ and attachment of the acetyl group to thiamine pyrophosphate. The subsequent steps involve redox reactions. Which of the following gives them in the order in which they occur? * A. reduction of NAD+ , oxidation of reduced lipoic acid, reduction of lipoic acid with attachment of the acetyl to lipoate, reduction of FAD * B. reduction of FAD, oxidation of reduced lipoic acid, reduction of NAD+ , reduction of lipoic acid with attachment of the acetyl to lipoate * C. reduction of lipoic acid with attachment of the acetyl to lipoate, oxidation of reduced lipoic acid, reduction of FAD, reduction of NAD+ * D. oxidation of reduced lipoic acid, reduction of NAD+ , reduction of lipoic acid with attachment of the acetyl to lipoate, reduction of FAD * E. none of the above

Answer 115

C. reduction of lipoic acid with attachment of the acetyl to lipoate, oxidation of reduced lipoic acid, reduction of FAD, reduction of NAD+

Question 116

# 2014 Which of the TCA cycle reactions yields reducing power directly, i.e. NADH or FADH2? * A. the citrate synthase reaction * B. conversion of succinate to fumarate * C. the aconitase reaction * D. conversion of fumarate to malate * E. more than one of these

Answer 116

B. conversion of succinate to fumarate

Question 117

# 2014 If succinyl-CoA labeled with ¹⁴C in C1 (which carries the CoA) is converted to fumarate, the label will appear in fumarate * A. equally in C1 and C2 * B. equally in c2 and c3 * C. only in c1 * D. only in c4 * E. equally in c1 and c4

Answer 117

equally in c1 and c4

Question 118

# 2014 Several steps of the TCA cycle are regulated allosterically. Which of the following combinations would be expected to slow or stop the cycle from operating? * A. High AMP concentration and high NAD+ concentration * B. High calcium concentration and high ADP concentration * C. High ATP concentration and high NADH concentration * D. High CoASH concentration and high ADP concentration * E. all of the above

Answer 118

C. High ATP concentration and high NADH concentration

Question 119

# 2014 Although vertebrates cannot convert acetyl-CoA to carbohydrates, plants can by using the reactions of the glyoxylate cycle. For this bypass to work they must pass an intermediate that they make in peroxisomes or glyoxisomes to the TCA cycle in mitochondria. Which of the following is the intermediate? * A. isocitrate * B. malate * C. acetyl-CoA * D. succinate * E. none of these

Answer 119

D. succinate

Question 120

# 2014 In the reaction of acetyl-CoA and oxaloacetate to form citrate, the cellular concentration of oxaloacetate is very low. The reaction is nevertheless essentially irreversible. Why? * A. Citrate builds up, pushing the reaction to the right * B. The standard free energy of the reaction is so strongly negative that the effect of the low OAA concentration is overcome. * C. Citrate synthase is a very active enzyme with a high kcat. * D. Allosteric interactions force the reaction to the right. * E. none of the above

Answer 120

B. The standard free energy of the reaction is so strongly negative that the effect of the low OAA concentration is overcome.

Question 121

# 2014 The iron in FeS clusters usually participates in reactions by * A. reducing disulfides to SH groups. * B. oxidizing SH groups to disulfides * C. gaining or losing an electron according the reaction Fe++ → Fe+++ + e * D. binding or releasing sulfur atoms * E. consuming radical oxygen species

Answer 121

C. gaining or losing an electron according the reaction Fe++ → Fe+++ + e

Question 122

# 2015 What is the cost (in ATP equivalents) of transforming glucose to pyruvate via glycolysis and back again to glucose via gluconeogenesis? * A. 1 * B. 2 * C. 3 * D. 4 * E. 5

Answer 122

D. 4

Question 123

# 2015 Starting with fructose 1,6 bisphosphate and incubating with all glycolytic enzymes and cofactors what is the yield of ATP? * A. 1 * B. 2 * C. 3 * D. 4 * E. 5

Answer 123

D. 4

Question 124

# 2015 The conversion of 1 mol of fructose 1,6-bisphosphate to 2 mol of pyruvate by the glycolic pathway results in a net formation of: * A. 1 mol of NAD+ and 2 mol of ATP. * B. 1 mol of NADH and I mol of ATP. * C. 2 mol of NADH and 2 mol of ATP. * D. 2 mol of NADH and 4 mol of ATP. * E. 2 mol of NAD+ and 4 mol of ATP.

Answer 124

D. 2 mol of NADH and 4 mol of ATP.

Question 125

# 2015 Oxaloacetate uniformly labeled with 14C (i.e., with equal amounts of 14C in each of its carbon atoms) is condensed with unlabeled acetyl-CoA. After a single pass through the citric acid cycle back to oxaloacetate, what fraction of the original radioactivity will be found in the oxaloacetate? * A. all * B. 1/2 * C. 1/3 * D. 1/4 * E. 3/4

Answer 125

B. 1/2

Question 126

# 2015 Which of the following statements apply (applies) to the β oxidation of fatty acids? 1. The process takes place in the cytosol of mammalian cells. 2. Carbon atoms are removed from the acyl chain one at a time. 3. Before oxidation, fatty acids must be converted to their CoA derivatives. 4. NADP+ is the electron acceptor. 5. The products of β oxidation can directly enter the citric acid cycle for further oxidation. * A. 1, 2 and 3 * B. 1, 2 and 5 * C. 3 and 5 only * D. l and 3 only * E. 4 only

Answer 126

C. 3 and 5 only

Question 127

# 2015 Acetyl-CoA labeled with ¹⁴C in both of its acetate carbon atoms is incubated with unlabeled oxaloacetate and a crude tissue preparation capable of carrying out the reactions of the citric acid cycle. After one turn of the cycle, oxaloacetate would have ¹⁴C in: * A. all four carbon atoms. * B. no pattern that is predictable from the information provided. * C. none of its carbon atoms. * D. the keto carbon and one of the carboxyl carbons. * E. the two carboxyl carbons.

Answer 127

A. all four carbon atoms.

Question 128

# 2015 The two moles of CO2 produced in the first turn of the citric acid cycle have their origin in the: * A. carboxyl and methylene carbons of oxaloacetate * B. carboxyl group of acetate and a carboxyl group of oxaloacetate. * C. carboxyl group of acetate and the keto group of oxaloacetate. * D. two carbon atoms of acetate. * E. two carboxyl groups derived from oxaloacetate.

Answer 128

E. two carboxyl groups derived from oxaloacetate

Question 129

# 2015 Which of the enzymatic steps of the TCA cycle listed below is irreversible under cellular conditions? * A. aconitase * B. isocitrate dehydrogenase * C. succinate dehudrogenase * D. fumarase * E. None of these is irreversible under cellular conditions

Answer 129

B. isocitrate dehydrogenase

Question 130

# 2015 If electron transport is operating, * A. the pH in the mitochondrial matrix will be lower than in the intermembrane space. * B. the pH in the mitochondrial matrix will be higher than in the intermembrane space. * C. the pH in the mitochondrial matrix will be the same as in the intermembrane space. * D. the pH in the two compartments will differ only when electron transport starts. * E. cannot tell from data givem.

Answer 130

B. the pH in the mitochondrial matrix will be higher than in the intermembrane space.

Question 131

# 2015 The normal physiological role of ATP synthase is * A. to pump protons out of the mitochondrion. * B. to catalyze ATP hydrolysis. * C. to use the proton electrochemical gradient to phosphorylate ADP. * D. to use ATP to drive metabolic reactions. * E. more than one of the above.

Answer 131

C. to use the proton electrochemical gradient to phosphorylate ADP.

Question 132

# 2015 Glycolysis produces two molecules of pyruvate from one molecule of glucose. If each pyruvate is then converted to acetyl-CoA, and if each acetyl-CoA undergoes one turn of the TCA cycle, how many electrons will enter the electron transport chain? * A. None * B. Four * C. Six * D. Twenty * E. none of these is correct

Answer 132

D. Twenty

Question 133

# 2015 Which of the hemes shown below cannot be removed from its protein even if the protein is fully unfolded? * A. Protoporphryn IX * B. Heme C * C. Heme A * D. All can be removed upon unfolding the protein. * E. None can be removed by unfolding the protein.

Answer 133

B. Heme C

Question 134

# 2015 How many molecules of NADH would be necessary to convert a 4Fe-4S iron sulfur center from a fully oxidized state to a fully reduced state? * A. None. NADH cannot interact directly or indirectly with 4Fe-4S centers. * B. One * C. Two * D. Four * E. None of the above

Answer 134

C. Two

Question 135

# 2015 Yeast cells grow in the absence of oxygen, consuming glucose for energy and producing ethanol. If exposed to air, they consume much less oxygen and cease to make ethanol. Why? * A. Oxygen inactivates the enzyme that converts pyruvate to ethanol. * B. Oxygen slows the growth of the culture so less glucose is needed, and the cells use the ethanol instead. * C. Oxygen is an allosteric inhibitor of glycolytic enzymes, reducing their activity. * D. Oxygen allows the electron transport chain to operate, so that each glucose molecule yields more energy, thereby reducing the amount of glucose required for growth and avoiding diversion of pyruvate to ethanol. * E. More than one of the above

Answer 135

D. Oxygen allows the electron transport chain to operate, so that each glucose molecule yields more energy, thereby reducing the amount of glucose required for growth and avoiding diversion of pyruvate to ethanol.

Question 136

# 2016 How many of the TCA cycle reactions involve oxidations, i.e. production of NADH or FADH2? * A. none * B. one * C. two * D. three * E. more than three

Answer 136

E. more than three

Question 137

# 2016 How many complete turns of the TCA cycle would be required to produce four molecules of CO2? * A. none * B. one * C. two * D. three * E. more than three

Answer 137

C. two

Question 138

# 2016 How many net water molecules are produced when aconitase converts citrate to isocitrate? * A. none * B. one * C. two * D. three * E. more than three

Answer 138

* A. none

Question 139

# 2016 Lipoic acid is a key part of the pyruvate dehydrogenase complex. It participates in the oxidative decarboxylation of pyruvate, becoming reduced in the process, and is, in turn, reoxidized in preparation for another catalytic cycle. Which of the following is true of lipoic acid? * A. It contains a nicotinamide group like that in NAD+ . * B. It contains a flavin like that in FAD. * C. It interacts directly with NAD+ when it is reoxidixed. * D. It swings from the active site where it is oxidized to the site where it is reduced. * E. More than one of these.

Answer 139

D. It swings from the active site where it is oxidized to the site where it is reduced.

Question 140

# 2016 Which of the following is NOT involved in oxidative decarboxylations such as those catalyzed by αketoglutarate dehydrogenase, pyruvate dehydrogenase, and the enzyme catalyzing oxidation of isoleucine? * A. CoA-SH is produced * B. NADPH is produced * C. NAD+ is produced * D. CO2 is produced * E. All the above are correct

Answer 140

B. NADPH is produced

Question 141

# 2016 Which of the following reactions would cause the position of a radioactively labeled carbon atom to be scrambled so its origin in acetyl-CoA could no longer be accurately determined? * A. Citrate synthase * B. succinate dehydrogenase * C. fumarase * D. Succinyl-CoA synthetase * E. None of these

Answer 141

D. Succinyl-CoA synthetase

Question 142

# 2016 In muscle tissue, Ca++ signals contraction, and it also stimulates energy-yielding metabolism to replace the ATP consumed by contraction. The effect of calcium on α-ketoglutrate dehydrogenase activity would be expected to * A. shift the sigmoid Vo versus [S] curve to the right. * B. shift the sigmoid Vo versus [S] curve to the left. * C. inhibit the enzyme * D. reduce the amount of NADH produced in the reaction. * E. None of the above

Answer 142

B. shift the sigmoid Vo versus [S] curve to the left.

Question 143

# 2016 In plants, some invertebrates and some microorganisms, carbohydrate biosynthesis is made possible by * A. the TCA cycle * B. glycolysis and gluconeogenesis * C. the glyoxylate cycle * D. all of these combined * E. none of these

Answer 143

D. all of these combined

Question 144

# 2016 Which statement is not true of phosphofructokinase-1 * A. It is inhibited by fructose 2,6-bisphosphate. * B. It is activated by AMP. * C. It is inhibited by citrate. * D. It is inhibited by ATP. * E. ATP increases the K0.5 (the effective Km) for fructose 6-phosphate

Answer 144

A. It is inhibited by fructose 2,6-bisphosphate.

Question 145

# 2016 Which of the following statements about photosystem II is correct? * A. It is located in the inner mitochondrial membrane. * B. It contains the electron carrier with the most negative E’o in the entire photosynthetic system. * C. It contains a Mn-containing complex which splits water. * D. Its final electron acceptor is NADPH. * E. Water is the only electron donor capable of regenerating P680 from P680\*.

Answer 145

C. It contains a Mn-containing complex which splits water.

Question 146

# 2016 Which of the following statements about cyclic photophosphorylation and non-cyclic photophosphorylation is correct? (from a posted exam) * A. Cyclic photophosphorylation involves only photosystem II and produces only ATP; non-cyclic photophosphorylation involves photosystems I and II and also produces only ATP. * B. Both pathways liberate oxygen. * C. Both pathways involve photosystems I and II. * D. Cyclic photophosphorylation reduces NADP+ and liberates oxygen; non-cyclic photophosphorylation reduces NADP+ but does not liberate oxygen. * E. Non-cyclic photophosphorylation reduces NADP+ and liberates oxygen; cyclic photophosphorylation produces ATP but does not liberate oxygen.

Answer 146

E. Non-cyclic photophosphorylation reduces NADP+ and liberates oxygen; cyclic photophosphorylation produces ATP but does not liberate oxygen.

Question 147

# 2016 Some photosynthetic prokaryotes use H2S, hydrogen sulfide, instead of water as their photosynthetic hydrogen donor. How does this change the ultimate products of photosynthesis? * A. Carbohydrate (CH2O) is not produced. * B. H2O is not produced. * C. Oxygen is not produced. * D. ATP is not produced. * E. The products do not change.

Answer 147

C. Oxygen is not produced.

Question 148

# 2016 What is the difference between inhibitors and uncouplers of oxidative phosphorylation? * A. Inhibitors stop electron transport but allow evolution of oxygen. * B. Uncouplers stop electron transport but allow evolution of oxygen. * C. Inhibitors allow electron transport but stop evolution of oxygen. * D. Uncouplers allow electron transport but stop evolution of oxygen. * E. None of the above is correct.

Answer 148

E. None of the above is correct.

Question 149

The structure of ubiquinone is shown below. The ring part undergoes oxidation/reduction reactions. What is the function of the isoprenoid side chain? * A. It is a left over from the biochemical synthesis of ubiquinone. * B. It serves as a precursor in steroid biosynthesis. * C. It helps control the rates of oxidation and reduction. * D. It keeps the molecule within the membrane bilayer. * E. none of the above

Answer 149

D. It keeps the molecule within the membrane bilayer.

Question 150

# 2016 Which of the proteins involved in electron transport is also a TCA cycle enzyme? * A. NADH dehydrogenase * B. cytochrome oxidase * C. succinate dehydrogenase * D. malate dehydrogenase * E. none of these

Answer 150

C. succinate dehydrogenase

Question 151

# 2016 How many molecules of cytochrome c are required to fully oxidize reduced ubiquinone (QH2) to Q via catalysis by ubiquinone: cytochrome c oxidoreductase? * A. None. Cytochrome c serves a catalytic role in this complex and undergoes no net change. * B. One * C. Two * D. Four * E. None of these answers is correct.

Answer 151

C. Two

Question 152

# 2016 How many ATP molecules does it take to move one long chain fatty acyl-CoA across the inner mitochondrial membrane? * A. None * B. One * C. Two * D. Four * E. None of these answers is correct.

Answer 152

A. None

Question 153

# 2016 The enzymes of fatty acid catabolism are listed below. In which order do they act to remove acetyl-CoA from a fattyacyl-CoA? * 1. enoyl CoA hydratase * 2. acyl-CoA dehydrogenase * 3. acyl-CoA acetyltransferase (thiolase) * 4. β-hydroxyacyl-CoA dehydrogenase * A. 1, 2, 3, 4 * B. 2, 1, 4, 3 * C. 4, 2, 3, 1 * D. 3, 3, 1, 4 * E. None of these sequences is correct.

Answer 153

B. 2, 1, 4, 3

Question 154

# 2016 Why are auxiliary enzymes needed for conversion of unsaturated fatty acids to acetyl-CoA? * A. They shift double bonds to allow for β-oxidation. * B. They reduce double bonds which would otherwise obstruct β-oxidation. * C. They convert cis double bonds to trans, as the β-oxidation enzymes cannot handle cis structures. * D. They activate the normal β-oxidation enzymes so those enzymes can handle unsaturation. * E. more than one of the above

Answer 154

E. more than one of the above

Question 155

# 2015 In fatty acid biosynthesis acyl-CoA carboxylase is activated by a phosphatase and inactivated by c-AMP dependent protein kinase A (PKA). Which of the following statements about its regulation is correct? * A. PKA activity is stimulated by high blood glucose. * B. The phosphatase activity is stimulated by low blood glucose. * C. When blood glucose is high, the carboxylase produces malonyl-CoA, which shuts off transfer of fatty acids to the mitochondrion. * D. When the carboxylase is activated, fatty acid catabolism is turned off. E. more than one of the above * E. more than one of the above

Answer 155

E. more than one of the above

Question 156

# 2016 What do lipoic acid, the acyl carrier protein and biotin have in common? * A. All are found at the ends of long swinging arms that move them from one active site to another. * B. They are attached non-covalently to their proteins. * C. All involve SH groups or disulfides in their functions. * D. They have carbohydrate attached to them. * E. They have nothing at all in common

Answer 156

A. All are found at the ends of long swinging arms that move them from one active site to another.

Question 157

# 2016 In which of the steps of fatty acid oxidation do mitochondria and peroxisomes differ? * A. the first oxidation → c=c double bond * B. hydration of the double bond * C. the second oxidation to the β-ketacyl-CoA * D. the thiolytic cleavage that yields an acetyl-CoA * E. more than one of the above

Answer 157

E. more than one of the above

Question 158

# 2016 The CO₂ required in fatty acid biosynthesis * A. becomes part of the growing carbon chain. * B. serves as the main buffer in the local environment as bicarbonate ion. * C. is first used and then removed, never entering the final product. * D. activates the synthetic system. * E. deactivates the synthetic system

Answer 158

C. is first used and then removed, never entering the final product

Question 159

# 2016 Why do plants and bacteria add double bonds beyond carbon nine, while animals do not? * A. They arose earlier in evolution. * B. They are metabolically more complex than animals. * C. Because they can’t make or use cholesterol. * D. The extra double bonds make adaptation to temperature changes possible. E. none of the above

Answer 159

D. The extra double bonds make adaptation to temperature changes possible. E. none of the above

Question 160

# 2019 Glycolysis ends with _____ and feeds its end product to the TCA cycle as \_\_\_\_\_. * A. phosphoenol pyruvate, ATP * B. glyceraldehyde 3-P, dihydroxyacetone phosphate * C. 1,3-bisphosphoglycerate, 2-phosphoglycerate * D. pyruvate, acetyl-CoA * E. none of the above

Answer 160

D. pyruvate, acetyl-CoA

Question 161

# 2019 How many glycolysis intermediates or products yield amino acids upon direct transamination? * A. None * B. One * C. Two * D. Three * E. more than three

Answer 161

B. One

Question 162

# 2019 Which of the following glycolytic intermediates/products does NOT contribute to the carbon skeleton of aromatic amino acids? * A. Pyruvate * B. Phosphoenolpyruvate * C. 3-Phosphoglyceric acid * D. Acetyl CoA E. * None of the above contribute

Answer 162

D. Acetyl CoA E.

Question 163

# 2019 How many complete turns of the TCA cycle would be required to produce six molecules of CO2? * A. none * B. one * C. two * D. three * E. more than three

Answer 163

D. three

Question 164

# 2019 Which of the following is produced in oxidative decarboxylations such as those catalyzed by α-ketoglutarate dehydrogenase, pyruvate dehydrogenase, and the enzyme catalyzing oxidation of isoleucine? * A. CoA-SH * B. NADPH * C. NAD+ * D. CO2 * E. All these are produced

Answer 164

D. CO2

Question 165

# 2019 What is the order of reactions in the β-oxidation of fatty acids? * 1. formation of a carbonyl group * 2. formation of a carbon-carbon double bond * 3. hydration * 4. consumption of a CoASH * A. 1, 2, 3, 4 * C. 4,3,2,1 * B. 2, 3, 1, 4 * D. 4,2,3,1 * E. none of these

Answer 165

B. 2, 3, 1, 4

Question 166

# 2019 Which of the following is/are consumed in the β-oxidation of palmitoyl-CoA to acetyl-CoA? * A. CoASH * B. FADH2 * C. NAD+ * D. more than one of these * E. none of these

Answer 166

D. more than one of these

Question 167

# 2019 How many protons does complex II (succinate dehydrogenase) pump across the inner mitochondrial membrane for each succinate oxidized to fumarate? * A. none * B. two * C. four * D. eight * E. none of these

Answer 167

A. none

Question 168

# 2019 Sodium azide acts on the mitochondrion the same way as cyanide. What will be its effect on energy metabolism by the mitochondrion? * A. There will be no effect at all; everything will proceed as normal. * B. The flow of electrons will cease. * C. Electrons will flow, but ATP will not be produced. * D. Electrons will flow, but oxygen will not be consumed. * E. None of these is correct

Answer 168

B. The flow of electrons will cease

Question 169

# 2019 The principal biochemical benefit of ubiquinone as an electron carrier is that * A. has a very high reduction potential, higher than the other electron carriers. * B. it aids both aerobic and anerobic metabolism. * C. it is ubiquitous throughout the cell, being found in all intracellular spaces. * D. it can handle one electron at a time, unlike NADH and FADH2, which can only transfer two at a time. * E. none of these is the main benefit.

Answer 169

D. it can handle one electron at a time, unlike NADH and FADH2, which can only transfer two at a time.

Question 170

# 2019 What did Dorothy Crowfoot Hodgkin win the Nobel prize for? * A. Determining the three dimensional structure of insulin * B. Determining the role of biotin in fatty acid metabolism * C. Determining the three dimensional structure of vitamin B12 * D. Working out the path of fatty acid degradation * E. none of the above

Answer 170

C. Determining the three dimensional structure of vitamin B12

Question 171

# 2019 Which of the following describes photorespiration? * A. Rubisco oxygenates ribulose 1,5-bisphosphate. * B. Photorespiration generates glycolate, which is toxic. * C. Oxygen is consumed and CO2 is produced as in mitochondrial respiration. * D. Carbon, first fixed by photosynthesis into carbohydrate, is then lost. * E. all of the above

Answer 171

E. all of the above

Question 172

# 2019 In the research presented by South et al. in Science Magazine, biochemical engineering was used to circumvent photorespiration. What did they do? * A. In Alternate Pathway 1 (AP1) genes from E. coli that convert glycolate to glycerate were introduced into the chloroplast. * B. Participation in photorespiration of peroxisomal and mitochondrial pathways was avoided. * C. In AP2 genes were introduced into the chloroplast that converted glycolate to malate. * D. In AP3 undesirable genes were deleted * E. more than one of the above

Answer 172

E. more than one of the above

Question 173

# 2019 Of the three biochemically engineered constructs created by South et al. and introduced into tobacco plants * A. all showed the same biomass increases in field trials. * B. one had an approximately 40% increase in biomass. * C. two failed to show any biomass increase * D. the greenhouse results were radically different from the field trial results. * E. none of the above

Answer 173

B. one had an approximately 40% increase in biomass

Question 174

# 2019 In the best of South et al.’s tobacco modifications * A. photosynthesis operated at a higher rate than in wild type. * B. more ATP was generated by photosynthesis than in wild type. * C. little or no fixed carbon was lost to photorespiration. * D. the plants became intolerant of high light levels. * E. more than one of the above

Answer 174

C. little or no fixed carbon was lost to photorespiration.

Question 175

# 2020 What would be the net result of the phosphofructokinase-1 and fructose bisphosphatese-1 reactions? ## Footnote A. loss of ATP by hydrolysis B. increased gluconeogenesis C. the synthesis of high energy phosphate bonds D. no net change; their actions cancel one another. E. none of the above

Answer 175

A. loss of ATP by hydrolysis

Question 176

# 2020 How many NADH molecules are generated when one molecule of glucose is converted to pyruvate? * A. none * B. one * C. two * D. three * E. more than three

Answer 176

C. two

Question 177

# 2020 Imagine that one molecule of glucose is converted to two molecules of pyruvate by glycolysis and then back to glucose by gluconeogenesis. What will be the net direct change in the number of high energy phosphate bonds (i.e. ATP equivalents) if NAD⁺ and NADH are ignored? * A. +2 * B. +4 * C. -2 * D. -4 * E. zero

Answer 177

D. -4

Question 178

# 2020 When sedoheptulose 7-phosphate is produced from ribose 5-phosphate and xylulose 5-phosphate in the pentose phosphate pathway, what other product is produced in the reaction? * A. glyceraldegyde 3-phosphate * B. erythrose 4-phosphate * C. fructose 6-phosphate * D. glucose 6-phosphate * E. none of these

Answer 178

A. glyceraldegyde 3-phosphate

Question 179

# 2020 Why does a mutation in which people have less glucose 6-phosphate dehydrogenase (G6PD) than normal cause them to be resistant to malaria? * A. The NADPH generated by the enzyme kills *Plasmodium falciparum*, the malaria parasite, directly. * B. *P. falciparum* is very sensitive to damage by radical oxygen. People who have less glucose 6-phosphate dehydrogenase than normal generate less NADPH, which, if in sufficient quantity, would destroy radical oxygen that would otherwise kill the parasite. * C. The red cells of people with G6PD deficiency don’t sickle. * D. The pentose phosphate pathway in G6PD deficient people does not generate enough nucleic acid precursors for the parasite to survive. * E. none of these

Answer 179

B. *P. falciparum* is very sensitive to damage by radical oxygen. People who have less glucose 6-phosphate dehydrogenase than normal generate less NADPH, which, if in sufficient quantity, would destroy radical oxygen that would otherwise kill the parasite.

Question 180

# 2020 When glycogen is hydrolyzed by glycogen phosphorylase, the product is * A. glucose * B. glucose 6-phosphate * C. pyruvate * D. glucose 1-phosphate * E. none of these

Answer 180

D. glucose 1-phosphate

Question 181

# 2020 If one glucose molecule is subjected to glycolysis and if both the resulting acetyl-CoA molecules pass through the TCA cycle (two turns of the cycle), how many pairs of electrons are produced? * A. two * B. four * C. six * D. eight * E. none of these

Answer 181

E. none of these

Question 182

# 2020 In the pyruvate dehydrogenase reaction the disulfide of lipoic acid is reduced and must be oxidized back to the disulfide form if the enzyme is to catalyze action on another pyruvate molecule. What supplies the oxidizing power? * A. NAD+ * B. NADH * C. CoA-SH * D. another molecule of lipoic acid * E. none of these

Answer 182

A. NAD+

Question 183

# 2020 At which of the following steps of the TCA cycle does oxidative decarboxylation occur? * A. succinate dehydrogenase * B. fumarase * C. a-ketoglutarate dehydrogenase * D. aconitase * E. more than one of these

Answer 183

C. a-ketoglutarate dehydrogenase

Question 184

# 2020 Why would AMP or ADP allosterically stimulate some of the TCA cycle enzymes? * A. They fit into binding sites into which ATP cannot fit. * B. Their presence at elevated concentrations implies that the cell needs ATP, so the enzymes are “turned on.” * C. Their presence at elevated concentrations implies that the cell’s NAD+ concentration is too low. * D. The statements is incorrect; it is calcium that stimulates the enzymes. * E. None of the above

Answer 184

B. Their presence at elevated concentrations implies that the cell needs ATP, so the enzymes are “turned on.”

Question 185

# 2020 Which TCA cycle intermediate yields aapartic acid in a one-step reaction? * A. pyruvate * B. citrate * C. a-ketoglutarate * D. oxaloacetate * E. more than one of these

Answer 185

D. oxaloacetate

Question 186

# 2020 The following fatty acid, in which the indicated carbon is labeled with ¹⁴C but the other carbons are ¹²C, is fed to an animal: ¹⁴CH₃(CH₂)₉COOH After allowing 30 minutes for fatty acid b oxidation, the label would most likely be recovered in: * A. acetyl-CoA. * B. beta-hydroxy butyryl-CoA. * C. both acetyl-CoA and propionyl-CoA. * D. palmitoyl-CoA. * E. propionyl-CoA.

Answer 186

E. propionyl-CoA.

Question 187

# 2020 In the oxidation of linoleic acid (18:2(cis-D⁹,cis-D¹²)), the double bonds require the action of enoyl CoA isomerase and dienoyl CoA reductase, which yield trans- D²-decanoyl-CoA, shown below. The process is completed by four b-oxidation cycles. In the first of these cycles, one step in the usual b-oxidation is skipped. Which step? * A. enoyl-CoA hydratase * B. thiolase * C. b-hydroxyacyl-CoA dehydrogenase * D. acyl-CoA dehydrogenase * E. none of these: no step is skipped

Answer 187

D. acyl-CoA dehydrogenase

Question 188

# 2020 What is the role of acetyl-CoA carboxylase (ACC) in the regulation of fatty acid metabolism? * A. When activated by a phosphatase whose activity is stimulated by insulin when blood glucose is high it catalyzes formation of malonyl-CoA, leading to fatty acid synthesis. * B. When blood glucose is low, it is inactivated by cAMP-dependent protein kinase A (PKA), which is stimulated by glucagon. Malonyl-CoA is therefore not formed, and fatty acid synthesis is prevented. * C. It activates the carnitine shuttle. * D. A and B * E. It has no role in fatty acid metabolism.

Answer 188

D. A and B

Question 189

# 2020 Cyclic electron flow in chloroplasts produces: A. ATP and O2, but not NADPH. B. ATP, but not NADPH or O2 . C. NADPH, and ATP, but not O2 . D. NADPH, but not ATP or O2 . E. O2, but not ATP or NADPH.

Answer 189

A. ATP and O2, but not NADPH.

Question 190

# 2020 Why does ubiquinone diffuse freely within the mitochondrial inner membrane while not escaping to the matrix or intermembrane space? * A. It is covalently anchored to a type of molecule which is a diffusible membrane component. * B. Its unusual distribution of oxygen atoms renders it lipid soluble. * C. It has a large hydrophobic tail. * D. Its interactions with protein electron carriers are so fast it doesn’t have time to escape but slow enough to allow diffusion. * E. none of the above

Answer 190

C. It has a large hydrophobic tail.

Question 191

# 2020 How many molecules of cytochrome c are required to fully oxidize reduced ubiquinone (QH2) to Q via catalysis by ubiquinone: cytochrome c oxidoreductase? * A. None. Cytochrome c serves a catalytic role in this complex and undergoes no net change. * B. One * C. Two * D. Four * E. None of these answers is correct.

Answer 191

C. Two

Question 192

# 2020 2,4-dinitrophenol, shown below, has a pKa of 4.0 for proton dissociation of the hydroxyl group. If we represent it as DNP-OH, the acid dissociation is DNP-OH ⇌ DNP-O- + H+. On the P side of the mitochondrial matrix, the DNP is in the protonated form. It passes easily through the membrane to the N side, where it dissociates and passes back through the membrane to the P side, and this cycle is repeated over and over. What will be the effect on energy metabolism by the mitochondrion? * A. There will be no effect at all; everything will proceed as normal. * B. The flow of electrons will cease. * C. Electrons will flow, but ATP will not be produced. * D. Electrons will flow, but oxygen will not be consumed. * E. None of these is correct

Answer 192

C. Electrons will flow, but ATP will not be produced

Question 193

# 2020 Ribulose 1 ,5-bisphosphate carboxylase/oxygenase is arguably the most important enzyme on earth because nearly all life is dependent, ultimately, on its action. The reactions catalyzed by this enzyme are influenced by: * A. pH * B. substrate concentration. * C. Mg²⁺ concentration. * D. temperature. * E. all of the above

Answer 193

E. all of the above

Question 194

# 2020 Of all the components of the "Z scheme," which has the lowest E'° (i.e., is the best reducing agent)? * A. P700 * B. P700\* * C. O₂ * D. H₂O * E. NADPH

Answer 194

B. P700\*