REVIEWER

Glycolysis, Gluconeogenesis and Krebs Cycle

1. The entry point into the citric acid cycle for isoleucine, valine, and
the product of odd-chain fatty acids is Succinyl CoA
2. The reactions of glycolysis occur in this eukaryotic cell
compartment Cytoplasm
3. All the following are allosteric effectors regulating key irreversible
enzymes of the glycolytic pathway except Ans. Glucose

4. Which one of the following enzymes is common to both glycolysis

and gluconeogenesis? Ans. Phosphoglycerate kinase

5. The following reactions all occur during oxidative decarboxylation

of pyruvate, except Ans. Oxidation of an acetate group

6. The citric acid cycle is considered to be the central metabolic

pathway for all the following reasons, except Ans. It links anaerobic
metabolism to aerobic metabolism.

7. Which enzyme catalyzes the conversion of succinyl-CoA into

succinate? Ans. Succinyl-CoA synthetase

8. Which group of small molecules best fit the boxes associated with
the reaction shown?

Ans. (a) NAD+ (b) NADH

9. Among the many molecules of high-energy phosphate compounds

formed as a result of the functioning of the citric acid cycle, one
molecule is synthesized at the substrate level. In which of the
following reactions does this occur? Ans. Alpha-ketoglutarate to
succinate

10. Which one of the following reactions is unique to

gluconeogenesis? Ans. Oxaloacetate → phosphoenolpyruvate
 11. Which one of the following enzymes catalyzes high-energy
phosphorylation of substrates during glycolysis? Ans.
Glyceraldehydes-3-phosphate dehydrogenase

12. How many ATPs (per glucose) are made via substrate-level
phosphorylation during glycolysis? Ans. 4

13. In the pathway, ATP is produced between Ans. G – H

14. Which enzyme catalyzes a reaction that is a major control point

for glycolysis? Ans. Phosphofructokinase

15. Which enzyme catalyzes the reaction shown? Ans. an isomerase

16. Which one of the following compounds is common to both the

oxidative branch and the non-oxidative branch of the pentose
phosphate pathway? Ans. Ribulose-5-phoshate
17. The order of compounds and intermediates found in the citric acid
cycle is as follows: Ans. Isocitrate --> aconitate --> α-ketoglutarate -->
fumarate --> malate --> oxaloacetate

18. Enzymes with the following name types are used in isomerization
reactions None of these

19. The synthesis of glucose from pyruvate by gluconeogenesis: Ans.

Requires the participation of biotin.

20. Which one of the following statements concerning glycolysis is

correct? Ans. The regulated reactions are also the irreversible
reactions.
 21. Which of the following occurs to fructose during catabolism? Ans.
It is phosphorylated in the first step.

22. In the figure, fructose-1,6-diphosphate is located at point. Ans. C

23. Reduction of which one of the following substrates leads to a

reducing equivalent in a step of the citric acid cycle? Ans. Malate

24. Compared with the resting state, vigorously contracting skeletal

muscle shows: Ans. an increased conversion of pyruvate to lactate.
25. The following enzyme catalyzed breaking fructose bisphosphate
into two 3-carbon units: Ans. Aldolase

26. All the following events occur during formation of

phosphoenolpyruvate from pyruvate during gluconeogenesis except
Ans. CoA is required

27. Which one of the following statements concerning

gluconeogenesis is correct? Ans. It is important in maintaining blood
glucose during the normal overnight fast.

28. The activity of pyruvate carboxylase is dependent upon the

positive allosteric effector Ans. Acetyl CoA

29. Which one of the following conditions decreases the oxidation of

acetyl CoA by the citric acid cycle? Ans. A low NAD+/NADH ratio

30. An enzyme that transfers a phosphate group from ATP to a

substrate is usually called Ans. a kinase

31. Which group of small molecules best fit the boxes associated with
the reaction shown? Ans. (a) FAD (b) FADH2
32. Familial galactosemia is toxic because Galactose is converted to
the toxic substance galactitol

33. An enzyme that involves substrate-level phosphorylation is Ans.

Succinyl-CoA to succinate

34. Which of enzyme catalyzes the reaction shown? Ans. Pyruvate

kinase

35. Which enzymes in the citric acid cycle catalyze oxidative

decarboxylation reactions? Ans. Isocitrate dehydrogenase and the α-
ketoglutarate dehydrogenase complex

36. Which one of the following reactions constitutes an isomerization?

Ans. Glucose-6-phosphate fructose-6-phosphate

37. Major metabolic pathways are considered to be either mainly

anabolic or catabolic. Which of the following pathways is most
correctly considered to be amphibolic? Ans. Citric acid cycle

38. These vitamins and enzyme cofactors are all used by the pyruvate
dehydrogenase complex during oxidative decarboxylation, except
Ans. All of these are used during oxidative decarboxylation.

39. Which of the following enzymes of the glycolytic pathway is

particularly sensitive to inhibition by fluoride ions? Ans. Enolase

40. Acetyl-CoA is arguably the most important intermediate in

metabolism, since it can be used for all of the following, except Ans.
Breakdown of CO2 and water, yielding much energy.

41. Control of the citric acid cycle is exercised by each of the following
enzymes, except for Ans. Aconitase

42. The conversion of pyruvate to acetyl CoA and CO2: Ans. involves
the participation of lipoic acid.
 43. Citrate has a positive allosteric effect on which one of the
following enzymes? Ans. Acetyl CoA carboxylase

44. In the normal resting state of humans, most of the blood glucose
burned as fuel is consumed by Ans. the brain

45. Which one of the following enzymes catalyzes phosphorylation

with the use of inorganic phosphate? Ans. Glyceraldehydes-3-
phosphate dehydrogenase

Quiz on Glycogenesis, Glycogenolysis, Fatty acid synthesis, Fatty acid breakdown

1. Which of these polysaccharides does not function as structural
components of organisms? Ans. Glycogen
2. During the breakdown of glycogen, free glucose is formed from
which of the following? Ans. Glucose residues at alpha(1 - 6)
linkage
3. Which of the following does not occur when a single glucose
molecule is transferred from UDP-glucose to a growing glycogen?
Ans. The glucose can be attached to a #6 carbon atom in the
glycogen molecule, by a branching enzyme
4. Consider the case of an athlete who has just completed a work
out. At this point, the athlete consumes a sports drink, which
contains a large amount of glucose, which enters the circulation.
Glycogen degradation is inhibited in the liver under these
conditions, prior to insulin release, due to allosteric inhibition of
which of the following enzymes? Ans. Phosphorylase a
5. Which of the following best differentiates glycogenolysis? Ans.
Glycogenesis requires energy to start the reaction; glycogenolysis
releases energy
6. The hormone that opposes the actions of insulin: Ans. Glucagon
7. All of the following describe β-oxidation EXCEPT Ans. The 2-
carbon groups are eliminated from the methyl end of the fatty
acid
8. After a well-rounded breakfast, all the following would be
expected to occur except Ans. Increased rate of glycogenolysis
9. Which happens during the conversion of pyruvate to glucose in
gluconeogenesis? Ans. Biotin is required.
10. An individual is taking a serene walk in the park when he spots an
escaped alligator from the zoo. The individual runs away as fast as
he can. Glycogen degradation is occurring to supply glycolysis with
a substrate even before epinephrine has reached the muscle. This
is due to which of the following? Ans. Increase in sarcoplasmic
calcium levels
11. The active carrier of glucose units into the glycogen primer: Ans.
Glucose-1-phosphate
12. Which one of the following activities is simultaneously stimulated
by epinephrine in muscle and inhibited by epinephrine in liver?
Ans. Glycolysis
13. It is called as the debranching enzyme that is needed during
glycogen breakdown which removes α1-6 branches Ans. Amylo-
(1-->6) glucosidase
14. Glucose-6-phosphate is a substrate or product in all the following
pathways except Ans. Oxidative phosphorylation
15. Which of these hormones causes elevation of the level of glucose
in the blood? Ans. Glucagon and epinephrine
16. Glycogen synthetase, the enzyme involved in the biosynthesis of
glycogen, may Ans. be more specifically defined as UDP-glucose-
glycogen glucosyl transferase
17. All the following statements about the structure of glycogen are
true EXCEPT Ans. It is a copolymer of glucose and galactose
18. Reduction reactions during fatty acid synthesis utilize the following
Ans. NADPH
19. The enzyme glucose-6-phosphatase is only found in cells which
have the Ans. Ability to replenish the levels of glucose in the
blood
20. The active form of glucose in glycogenesis Ans. UDP-Glucose
21. The beta-oxidation of palmitic acid results in the formation of
approximately this many ATP? Ans. 129
22. The first product of glycogenolysis: Ans. Glucose-1-phosphate

23. The reactions involved in beta-oxidation of fatty acids include the

following: The correct answer is: III, II, IV, I

(I) Cleavage of acetyl CoA from the fatty acid

(II) Hydration of a double bond
(III) Formation of a C–C double bond
(IV) Oxidation of an alcohol
23. Going back to the individual who continues to run from the
alligator, the muscle begins to import glucose from the circulation.
This occurs due to which of the following? Ans. Increase in
intracellular AMP levels
24. Pathways common to many tissues include all the following
EXCEPT Ans. Ketogenesis
25. The hormones, epinephrine and glucagon have which one of the
following effects on glycogen metabolism in the liver?
Ans.
Glycogen phosphorylase is phosphorylated and active, whereas
glycogen synthase is phosphorylated and inactive.
26. The key regulatory enzyme of the pentose phosphate pathway is
positively regulated by Ans. NADP+
27. Which one of the following is an obligatory intermediate in the
conversion of ribose-5-phosphate to glucose-6-phosphate?
Ans. Xylulose-5-phosphate
28. Most of the reducing equivalents utilized for synthesis of fatty
acids can be generated from Ans. the pentose phosphate
pathway
29. All the following are needed to store blood glucose as glycogen
following a meal EXCEPT Ans. Glucose-6-phosphatase
30. A researcher is studying the HMP shunt pathway in extracts of red
blood cells, in the absence of NADP+, and in which PFK-1 has been
chemically inactivated. Which carbon substrates are required to
generate ribose-5-phosphate in this system? Ans. Fructose-6-
phosphate and glyceraldehyde-3-phosphate
31. How many NADPH are oxidized in the synthesis of palmitoyl-CoA
from eight molecules of acetyl CoA? Ans. 14
32. An individual has been eating a large number of oranges during
the winter months to protect against getting a cold. The excess
carbons of citrate can be used to produce glycogen in the liver.
Which one of the following liver enzymes is required for this
conversion to occur?
Ans. α-ketoglutarate dehydrogenase
33. A patient is a marathon runner and has visited his doctor to ask
about carbohydrate loading to increase his performance during a
race. For a full week prior to a race, he eats three meals a day of
pancakes, potatoes, brown rice, and pasta and does not exercise
at all. He has not noticed any success with this regimen. Which of
the following answers best explains why he is getting no benefit
from his “carb loading”?
Ans. He is not depleting glycogen stores prior to loading
34. During an overnight fast, the major source of blood glucose is
Ans. Hepatic glycogenolysis
35. The first three reactions of the β-oxidation pathway are analogous
to which reactions in the other pathways
Ans. Succinate → fumarate → malate → oxaloacetate

36. The compound uridinediphosphate glucose (UDPG) plays a role in

Ans. Glycogen synthesis
37. Positive signals for glycogen breakdown include increases in all the
following except Ans. Blood glucose

38. Which of the following mechanism control the activity of glycogen

phosphorylase? Ans. I and II

I. Covalent modification
 II. Inhibition of glycogen product
III. Allosteric changes caused by effector molecules

38. Advantages of fatty acids as a form of energy storage include all

the following, except Ans. Storage of fats in muscle tissues
makes it readily available for use during activity.
39. It serves as the glycogen primer in glycogen synthesis Ans.
Glycogenin
40. This branching enzyme is important during glycogen synthesis
wherein it brakes one of the α1-4 bond and transfers a block of
residues (usually about seven) to a more interior site in the
glycogen molecule, reattaching these by creating an α1-6 bond.
Ans. Amylo-(1-->4)-(1-->6) transglucosidase
41. A woman with nonclassical galactosemia is considering becoming
pregnant and is concerned that she will be unable to synthesize
lactose in order to breast-feed her child. Her physician, who recalls
her biochemistry, tells her this should not be a problem, and that
she will be able to synthesize lactose at the appropriate time. This
is true due to the presence of which of the following? Ans.
Phosphoglucomutase

42. Which of the following explains the advantages of fatty acids as

form of storage energy? Ans. I and II

(I) Fatty acids contain less oxygen than carbohydrates

(II) Their hydrophobic nature allows close packing in adipose tissues
(III) Storage of fats in muscles makes it readily available for use during
activity.

42. In which pathway involving carbohydrates requires activation of

glucose using uridine triphosphate? Ans. Glycogenesis

Quiz on PPP, Glycogenesis, and Glycogenolysis

1. A patient is a marathon runner and has visited his doctor to ask

about carbohydrate loading to increase his performance during a
race. For a full week prior to a race, he eats three meals a day of
pancakes, potatoes, brown rice, and pasta and does not exercise at
all. He has not noticed any success with this regimen. Which of the
following answers best explains why he is getting no benefit from his
“carb loading”? Ans. He is not depleting glycogen stores prior to
loading
2. The key regulatory enzyme of the pentose phosphate pathway is
positively regulated by Ans. NADP+

3. All the following are needed to store blood glucose as glycogen

following a meal EXCEPT Ans. Glucose-6-phosphatase

4. Which one of the following activities is simultaneously stimulated

by epinephrine in muscle and inhibited by epinephrine in liver? Ans.
Glycolysis

5. After a well-rounded breakfast, all the following would be expected

to occur except Ans. Increased rate of glycogenolysis

6. Glucose-6-phosphate is a substrate or product in all the following

pathways except Ans. Oxidative phosphorylation

7. Most of the reducing equivalents utilized for synthesis of fatty acids

can be generated from Ans. Pentose phosphate pathway

8. It is called as the debranching enzyme that is needed during

glycogen breakdown which removes α1-6 branches Ans. Amylo-(1--
>6) glucosidase

9. Pathways common to many tissues include all the following EXCEPT

Ans. Ketogenesis

10. All the following statements about the structure of glycogen are
true EXCEPT Ans. It is a copolymer of glucose and galactose

11. It serves as the glycogen primer in glycogen synthesis Ans.

Glycogenin

12. An individual has been eating a large number of oranges during

the winter months to protect against getting a cold. The excess
carbons of citrate can be used to produce glycogen in the liver. Which
one of the following liver enzymes is required for this conversion to
occur? Ans. α-ketoglutarate dehydrogenase

13. A woman with nonclassical galactosemia is considering becoming

pregnant and is concerned that she will be unable to synthesize
lactose in order to breast-feed her child. Her physician, who recalls
her biochemistry, tells her this should not be a problem, and that she
will be able to synthesize lactose at the appropriate time. This is true
due to the presence of which of the following? Ans.
Phosphoglucomutase

14. The hormones, epinephrine and glucagon have which one of the
following effects on glycogen metabolism in the liver?
Ans. Glycogen phosphorylase is phosphorylated and active, whereas
glycogen synthase is phosphorylated and inactive.

15. An individual is taking a serene walk in the park when he spots an

escaped alligator from the zoo. The individual runs away as fast as he
can. Glycogen degradation is occurring to supply glycolysis with a
substrate even before epinephrine has reached the muscle. This is
due to which of the following? Ans. Increase in sarcoplasmic calcium
levels

16. Consider the case of an athlete who has just completed a work
out. At this point, the athlete consumes a sports drink, which contains
a large amount of glucose, which enters the circulation. Glycogen
degradation is inhibited in the liver under these conditions, prior to
insulin release, due to allosteric inhibition of which of the following
enzymes? Ans. Phosphorylase a

17. Glycogen synthetase, the enzyme involved in the biosynthesis of

glycogen, may Ans. be more specifically defined as UDP-glucose-
glycogen glucosyl transferase

18. The compound uridinediphosphate glucose (UDPG) plays a role in

Ans. Glycogen synthesis

19. The active form of glucose in glycogenesis Ans. UDP-Glucose

20. This branching enzyme is important during glycogen synthesis

wherein it brakes one of the α1-4 bond and transfers a block of
residues (usually about seven) to a more interior site in the glycogen
molecule, reattaching these by creating an α1-6 bond. Ans. Amylo-
(1-->4)-(1-->6) transglucosidase

21. Positive signals for glycogen breakdown include increases in all the
following except Ans. Blood glucose

22. The active carrier of glucose units into the glycogen primer:
Ans. Glucose-1-phosphate

23. Gong back to the individual who continues to run from the
alligator, the muscle begins to import glucose from the circulation.
This occurs due to which of the following? Ans. Increase in
intracellular AMP levels

24. The hormone that opposes the actions of insulin: Ans. Glucagon

25. The first product of glycogenolysis: Ans. Glucose-1-phosphate

26. During an overnight fast, the major source of blood glucose is
Ans. Hepatic glycogenolysis

27. Which one of the following is an obligatory intermediate in the

conversion of ribose-5-phosphate to glucose-6-phosphate?
Ans. Xylulose-5-phosphate