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:
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.
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2 mol of ATP.
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2 mol of NADH.
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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
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dihydroxyacetone phosphate → glycerol 3-phosphate
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glucose 6-phosphate → fructose 6-phosphate
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isocitrate → α-ketoglutarate
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oxaloacetate → malate
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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
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In C-1 of ethanol and CO2
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In C-1 of ethanol only
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In C-2 (methyl group) of ethanol only
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In C-2 of ethanol and CO2
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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.
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1 mol of NADH and 1 mol of ATP.
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2 mol of NAD+ and 4 mol of ATP.
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2 mol of NADH and 2 mol of ATP.
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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.
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only the carbon atom carrying the OH.
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only the carboxyl carbon atom.
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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.
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It is an endergonic process.
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It results in net synthesis of ATP.
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It results in synthesis of NADH.
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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
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glycolysis does not occur to significant extent under aerobic conditions.
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muscle is metabolically less active under aerobic than anaerobic conditions.
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the lactic acid generated is rapidly incorporated into lipids under aerobic conditions.
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under aerobic conditions in muscle, the major energy-yielding pathway is the pentose phosphate pathway, which does not produce lactate.
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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.
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ethanol.
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glucose.
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hemoglobin.
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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
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
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If the concentrations of the two products are high relative to that of fructose 1,6-bisphosphate.
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The reaction will not go to the right spontaneously under any conditions because the ΔG'° is positive.
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Under standard conditions, enough energy is released to drive the reaction to the right.
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When there is a high concentration of fructose 1,6-bisphosphate relative to the concentration of products.
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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.
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all three carbons.
-
its carbonyl carbon.
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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.
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both A and C.
-
its carbonyl carbon.
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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.
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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?
Question 17
Question
In comparison with the resting state, actively contracting human muscle tissue has a:
Answer
-
higher concentration of ATP.
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higher rate of lactate formation.
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lower consumption of glucose.
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lower rate of consumption of oxygen
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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
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ATP synthesis.
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catalysis by phosphoglycerate kinase.
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oxidation of NADH to NAD+.
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the formation of 1,3-bisphosphoglycerate.
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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:
Question 20
Question
Which of the following is a cofactor in the reaction catalyzed by glyceraldehyde 3-phosphate dehydrogenase?
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
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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
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Phosphoenolpyruvate
-
Pyruvate
Question 23
Question
Glycogen is converted to monosaccharide units by:
Answer
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glucokinase.
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glucose-6-phosphatase
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glycogen phosphorylase.
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glycogen synthase.
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glycogenase.