Ch. 14

Question 1

Question

Glycolysis is the name given to a metabolic pathway occurring in many different cell types. It consists of 11 enzymatic steps that convert glucose to lactic acid. Glycolysis is an example of:

Answer

aerobic metabolism.
anabolic metabolism.
a net reductive process.
fermentation.
oxidative phosphorylation

Question 2

Question

The anaerobic conversion of 1 mol of glucose to 2 mol of lactate by fermentation is accompanied by a net gain of:

Answer

1 mol of ATP.
1 mol of NADH.
2 mol of ATP.
2 mol of NADH.
none of the above.

Question 3

Question

During strenuous exercise, the NADH formed in the glyceraldehyde 3-phosphate dehydrogenase reaction in skeletal muscle must be reoxidized to NAD+ if glycolysis is to continue. The most important reaction involved in the reoxidation of NADH is:

Answer

A) dihydroxyacetone phosphate → glycerol 3-phosphate B) glucose 6-phosphate → fructose 6-phosphate C) isocitrate → α-ketoglutarate D) oxaloacetate → malate E) pyruvate → lactate
dihydroxyacetone phosphate → glycerol 3-phosphate
glucose 6-phosphate → fructose 6-phosphate
isocitrate → α-ketoglutarate
oxaloacetate → malate
pyruvate → lactate

Question 4

Question

If glucose labeled with 14C in C-1 were fed to yeast carrying out the ethanol fermentation, where would the 14C label be in the products?

Answer

In C-1 of ethanol and CO2
In C-1 of ethanol only
In C-2 (methyl group) of ethanol only
In C-2 of ethanol and CO2
In CO2 only

Question 5

Question

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

Answer

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

Question 6

Question

In an anaerobic muscle preparation, lactate formed from glucose labeled in C-3 and C-4 would be labeled in:

Answer

all three carbon atoms.
only the carbon atom carrying the OH.
only the carboxyl carbon atom.
only the methyl carbon atom.
the methyl and carboxyl carbon atoms.

Question 7

Question

Which of the following statements is not true concerning glycolysis in anaerobic muscle?

Answer

Fructose 1,6-bisphosphatase is one of the enzymes of the pathway.
It is an endergonic process.
It results in net synthesis of ATP.
It results in synthesis of NADH.
Its rate is slowed by a high [ATP]/[ADP] ratio.

Question 8

Question

When a muscle is stimulated to contract aerobically, less lactic acid is formed than when it contracts anaerobically because:

Answer

glycolysis does not occur to significant extent under aerobic conditions.
muscle is metabolically less active under aerobic than anaerobic conditions.
the lactic acid generated is rapidly incorporated into lipids under aerobic conditions.
under aerobic conditions in muscle, the major energy-yielding pathway is the pentose phosphate pathway, which does not produce lactate.
under aerobic conditions most of the pyruvate generated as a result of glycolysis is oxidized by the citric acid cycle rather than reduced to lactate.

Question 9

Question

Glycolysis in the erythrocyte produces pyruvate that is further metabolized to:

Answer

CO2.
ethanol.
glucose.
hemoglobin.
lactate.

Question 10

Question

When a mixture of glucose 6-phosphate and fructose 6-phosphate is incubated with the enzyme phosphohexose isomerase, the final mixture contains twice as much glucose 6-phosphate as fructose 6-phosphate. Which one of the following statements is most nearly correct, when applied to the reaction below (R = 8.315 J/mol·K and T = 298 K)? Glucose 6-phosphate ↔ fructose 6-phosphate

Answer

ΔG'° is +1.7 kJ/mol.
ΔG'° is –1.7 kJ/mol.
ΔG'° is incalculably large and negative.
ΔG'° is incalculably large and positive.
ΔG'° is zero.

Question 11

Question

In glycolysis, fructose 1,6-bisphosphate 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 to the right?

Answer

If the concentrations of the two products are high relative to that of fructose 1,6-bisphosphate.
The reaction will not go to the right spontaneously under any conditions because the ΔG'° is positive.
Under standard conditions, enough energy is released to drive the reaction to the right.
When there is a high concentration of fructose 1,6-bisphosphate relative to the concentration of products.
When there is a high concentration of products relative to the concentration of fructose 1,6-bisphosphate.

Question 12

Question

Glucose labeled with 14C in C-1 and C-6 gives rise in glycolysis to pyruvate labeled in:

Answer

A and C.
all three carbons.
its carbonyl carbon.
its carboxyl carbon.
its methyl carbon.

Question 13

Question

If glucose labeled with 14C at C-1 (the aldehyde carbon) were metabolized in the liver, the first radioactive pyruvate formed would be labeled in:

Answer

all three carbons.
both A and C.
its carbonyl carbon.
its carboxyl carbon.
its methyl carbon.

Question 14

Question

In an anaerobic muscle preparation, lactate formed from glucose labeled in C-2 would be labeled in:

Answer

all three carbon atoms.
only the carbon atom carrying the OH.
only the carboxyl carbon atom.
only the methyl carbon atom.
the methyl and carboxyl carbon atoms.

Question 15

Question

If glucose labeled with 14C in C-3 is metabolized to lactate via fermentation, the lactate will contain 14C in:

Answer

all three carbon atoms.
only the carbon atom carrying the OH.
only the carboxyl carbon atom.
only the methyl carbon atom.
the methyl and carboxyl carbon atoms.

Question 16

Question

Which of these cofactors participates directly in most of the oxidation-reduction reactions in the fermentation of glucose to lactate?

Answer

ADP
ATP
FAD/FADH2
Glyceraldehyde 3-phosphate
NAD+/NADH

Question 17

Question

In comparison with the resting state, actively contracting human muscle tissue has a:

Answer

higher concentration of ATP.
higher rate of lactate formation.
lower consumption of glucose.
lower rate of consumption of oxygen
lower ratio of NADH to NAD+.

Question 18

Question

The steps of glycolysis between glyceraldehyde 3-phosphate and 3-phosphoglycerate involve all of the following except:

Answer

ATP synthesis.
catalysis by phosphoglycerate kinase.
oxidation of NADH to NAD+.
the formation of 1,3-bisphosphoglycerate.
utilization of Pi.

Question 19

Question

The first reaction in glycolysis that results in the formation of an energy-rich compound (i.e., a compound whose hydrolysis has a highly negative ΔG'°) is catalyzed by:

Answer

glyceraldehyde 3-phosphate dehydrogenase.
hexokinase.
phosphofructokinase-1.
phosphoglycerate kinase.
triose phosphate isomerase.

Question 20

Question

Which of the following is a cofactor in the reaction catalyzed by glyceraldehyde 3-phosphate dehydrogenase?

Answer

ATP
Cu2+
heme
NAD+
NADP+

Question 21

Question

In the phosphoglycerate mutase reaction, the side chain of which amino acid in the enzyme is transiently phosphorylated as part of the reaction?

Answer

serine
threonine
tyrosine
histidine
arginine

Question 22

Question

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?

Answer

2-phosphoglycerate
Glucose
Glyoxylate
Phosphoenolpyruvate
Pyruvate

Question 23

Question

Glycogen is converted to monosaccharide units by:

Answer

glucokinase.
glucose-6-phosphatase
glycogen phosphorylase.
glycogen synthase.
glycogenase.

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