836 - 863 Carbohydrate metabolism

Question 1

Identify the missing ‘S’ intermediate

Select one:
a. Glucose
b. Galactose
c. Fucose
d. Glucose-1-phosphate
e. 1,3-bisphosphoglycerate

Answer 1

a. Glucose

Question 2

Identify the missing ‘S’ intermediate.

Select one:
a. Glucose-6-phosphate
b. Glucose-1-phosphate
c. Galactolactone
d. Glucose-3-phosphate
e. 3-phosphoglycerate

Answer 2

a. Glucose-6-phosphate

Question 3

Identify the missing ‘S’ intermediate.

Select one:
a. 6-Phosphogluconolactone
b. Glucose-1-phosphate
c. Glyceraldehyde
d. 1-phosphogluconolactone
e. 6-hydroxy-gluconolactone

Answer 3

a. 6-Phosphogluconolactone

Question 4

Identify the missing ‘X’ cofactor.

Select one:
a. ATP, Mg2+
b. AMP, Mg2+
c. PPi, Mg2+
d. NAD
e. FAD

Answer 4

a. ATP, Mg2+

Question 5

Identify the missing ‘X’ cofactor.

Select one:
a. ADP, Mg2+
b. ATP, Mg2+
c. AMP, Mg2+
d. NADPH + H
e. FAD

Answer 5

a. ADP, Mg2+

Question 6

Identify the missing ‘X’ cofactor.

Select one:
a. NADP+
b. ATP
c. ADP
d. FADH + H+
e. NADH

Answer 6

a. NADP+

Question 7

Identify the missing ‘X’ cofactor.

Select one:
a. NADPH + H+
b. ATP, Mg2+
c. ADP, Mg2+
d. NADH + H+
e. Glucose

Answer 7

a. NADPH + H+

Question 8

Identify the missing ‘E’ enzyme.

Select one:
a. Hexokinase
b. Phosphatase
c. Lactone kinase
d. Hexophosphorylase
e. Phosphokinase

Answer 8

a. Hexokinase

Question 9

Identify the missing ‘E’ enzyme.

Select one:
a. Glucose-6-phosphate dehydrogenase
b. Glucose-3-phosphate dehydrogenase c
. Glucose-6-phosphate deacetylase
d. Hexophosphatase
e. Pyruvate kinase

Answer 9

a. Glucose-6-phosphate dehydrogenase

Question 10

Which of the following is a definition of glycemic index?

Select one:
a. The decrease in the blood concentration of glucagon after consuming the food compared with an equivalent amount 
of white bread.
b. The increase in the blood concentration of glucose after 
consuming the food.
c. The increase in the blood concentration of glucose after 
consuming the food compared with an equivalent amount of white bread.
d. The increase in the blood concentration of insulin after 
consuming the food.
e. The increase in the blood concentration of insulin after 
consuming the food compared with an equivalent amount of white bread.

Answer 10

c. The increase in the blood concentration of glucose after 
consuming the food compared with an equivalent amount of white bread.

Question 11

Which of the following will have the lowest glycemic index?

Select one:
a. baked apple
b. A baked potato
c. An uncooked apple
d. An uncooked potato
e. Apple juice

Answer 11

d. An uncooked potato

Question 12

Which of the following will have the highest glycaemic index?

Select one:
a. A baked apple
b. A baked potato
c. An uncooked apple
d. An uncooked potato
e. Apple juice

Answer 12

e. Apple juice

Question 13

A blood sample is taken from a 50-year-old woman after an overnight fast. Which one of the following will be at a higher concentration than after she had eaten a meal?

Select one:
a. Glucose
b. Insulin
c. Ketone bodies
d. Nonesterified fatty acids
e. Triacylglycerol

Answer 13

d. Nonesterified fatty acids

Question 14

A blood sample is taken from a 25-year-old man after he has eaten three slices of toast and a boiled egg. Which one of the following will be at a higher concentration than if the blood sample had been taken after an overnight fast?

Select one:
a. Alanine
b. Glucagon
c. Glucose
d. Ketone bodies
e. Nonesterified fatty acids

Answer 14

c. Glucose

Question 15

A blood sample is taken from a 40-year-old man has been fasting completely for a week, drinking only water. Which of the following will be at a higher concentration than after a normal overnight fast?

Select one:
a. Glucose
b. Insulin
c. Ketone bodies
d. Nonesterified fatty acids
e. Triacylglycerol

Answer 15

c. Ketone bodies

Question 16

Which one of following statements about the fed and fasting metabolic states is correct?


Select one:
a. In the fasting state glucagon acts to increase the activity of lipoprotein lipase in adipose tissue.
b. In the fasting state, glucagon acts to increase the synthesis of glycogen from glucose.
c. In the fed state insulin acts to increase the breakdown of glycogen to maintain blood glucose.
d. Ketone bodies are synthesized in liver in the fasting state, and the amount synthesized increase as fasting extends into starvation.
e. In the fed state there is decreased secretion of insulin in response to increased glucose in the portal blood.

Answer 16

d. Ketone bodies are synthesized in liver in the fasting state, and the amount synthesized increase as fasting extends into starvation.§

Question 17

Which one of following statements about the fed and fasting metabolic states is correct?


Select one:
a. In the fed state muscle can take up glucose for use as a metabolic fuel because glucose transport in muscle is stimulated in response to glucagon.
b. In the fed state there is decreased secretion of glucagon in response to increased glucose in the portal blood.
c. In the fed state, glucagon acts to increase the synthesis of glycogen from glucose.
d. Plasma glucose is maintained in starvation and prolonged fasting by gluconeogenesis from ketone bodies.
e. There is an increase in metabolic rate in the fasting state.

Answer 17

b. In the fed state there is decreased secretion of glucagon in response to increased glucose in the portal blood.

Question 18

Which one of following statements about the fed and fasting metabolic states is correct?

Select one:
a. In the fasting state muscle synthesizes glucose from amino acids.
b. In the fed state adipose tissue can take up glucose for synthesis of triacylglycerol because glucose transport in adipose tissue is stimulated in response to insulin.
c. Ketone bodies are synthesized in muscle in the fasting state, and the amount synthesized increases as fasting extends into starvation.
d. Ketone bodies provide an alternative fuel for red blood cells in the fasting state.
e. Plasma glucose is maintained in starvation and prolonged fasting by gluconeogenesis from fatty acids.

Answer 18

b. In the fed state adipose tissue can take up glucose for synthesis of triacylglycerol because glucose transport in adipose tissue is stimulated in response to insulin.

Question 19

Which one of following statements about the fed and fasting metabolic states is correct?

Select one:
a. In the fasting state adipose tissue synthesizes glucose from 
the glycerol released by the breakdown of triacylglycerol.
b. In the fasting state adipose tissue synthesizes ketone bodies.
c. In the fasting state the main fuel for red blood cells is fatty 
acids released from adipose tissue.
d. Ketone bodies provide the main fuel for the central nervous 
system in the fasting state.
e. Plasma glucose is maintained in starvation and prolonged fasting by gluconeogenesis in the liver from the amino acids released by the breakdown of muscle protein.

Answer 19

e. Plasma glucose is maintained in starvation and prolonged fasting by gluconeogenesis in the liver from the amino acids released by the breakdown of muscle protein.

Question 20

Which one of following statements about the fed and fasting metabolic states is correct?

Select one:
a. Fatty acids and triacylglycerol are synthesized in the liver in 
the fasting state.
b. In the fasting state the main fuel for the central nervous 
system is fatty acids released from adipose tissue.
c. In the fasting state the main metabolic fuel for most tissues 
comes from fatty acids released from adipose tissue.
d. In the fed state muscle cannot take up glucose for use as a 
metabolic fuel because glucose transport in muscle is 
stimulated in response to glucagon.
e. Plasma glucose is maintained in starvation and prolonged 
fasting by gluconeogenesis in adipose tissue from the glycerol released from triacylglycerol.

Answer 20

c. In the fasting state the main metabolic fuel for most tissues 
comes from fatty acids released from adipose tissue.

Question 21

A 25-year-old man visits his GP complaining of abdominal cramps and diarrhea after drinking milk. What is the most likely cause of his problem?

Select one:
a. Bacterial and yeast overgrowth in the large intestine
b. Infection with the intestinal parasite Giardia lamblia
c. Lack of pancreatic amylase
d. Lack of small intestinal lactase
e. Lack of small intestinal sucrase-isomaltase

Answer 21

d. Lack of small intestinal lactase

Question 22

Which one of following statements about glycolysis and gluconeogenesis is correct?

Select one:
a. All the reactions of glycolysis are freely reversible for 
gluconeogenesis.
b. Fructose cannot be used for gluconeogenesis in the liver 
because it cannot be phosphorylated to fructose-6- 
phosphate.
c. Glycolysis can proceed in the absence of oxygen only if 
pyruvate is formed from lactate in muscle.
d. Red blood cells only metabolize glucose by anaerobic 
glycolysis (and the pentose phosphate pathway).
e. The reverse of glycolysis is the pathway for gluconeogenesis 
in skeletal muscle.

Answer 22

d. Red blood cells only metabolize glucose by anaerobic 
glycolysis (and the pentose phosphate pathway).

Question 23

Which one of following statements about the step in glycolysis catalyzed by hexokinase and in gluconeogenesis by glucose 6-phosphatase is correct?

Select one:
a. Because hexokinase has a low Km its activity in liver 
increases as the concentration of glucose in the portal 
blood increases.
b. Glucose-6-phosphatase is mainly active in muscle in the 
fasting state.
c. If hexokinase and glucose-6-phosphatase are both equally 
active at the same time there is net formation of ATP from 
ADP and phosphate.
d. Liver contains an isoenzyme of hexokinase, glucokinase, 
which is especially important in the fed state
e. Muscle can release glucose into the circulation from its 
glycogen reserves in the fasting state.

Answer 23

d. Liver contains an isoenzyme of hexokinase, glucokinase, 
which is especially important in the fed state

Question 24

Which one of following statements about this step in glycolysis catalyzed by phosphofructokinase and in gluconeogenesis by fructose 1,6-bisphosphatase is correct?

Select one:
a. Fructose 1,6-bisphosphatase is mainly active in the liver in the fed state.
b. If phosphofructokinase and fructose 1,6-bisphosphatase are both equally active at the same time, there is a net formation of ATP from ADP and phosphate.
c. Phosphofructokinase is inhibited more or less completely by physiological concentrations of ATP.
d. Phosphofructokinase is mainly active in the liver in the fasting state.

Answer 24

c. Phosphofructokinase is inhibited more or less completely by physiological concentrations of ATP.

Question 25

Which one of the following statements about glucose metabolism in maximum exertion is correct?

Select one:
a. Gluconeogenesis from lactate requires less ATP than is formed during anerobic glycolysis.
b. In maximum exertion pyruvate is oxidized to lactate in muscle.
c. Oxygen debt is caused by the need to exhale carbon dioxide produced in response to acidosis.
d. Oxygen debt reflects the need to replace oxygen that has been used in muscle during vigorous exercise.
e. There is metabolic acidosis as a result of vigorous exercise

Answer 25

e. There is metabolic acidosis as a result of vigorous exercise

Question 26

Which one of following statements about glycogen metabolism is correct?

Select one:
a. Glycogen is synthesized in the liver in the fed state, then exported to other tissues in low density lipoproteins.
b. Glycogen reserves in liver and muscle will meet energy requirements for several days in prolonged fasting.
c. Liver synthesizes more glycogen when the hepatic portal blood concentration of glucose is high because of the activity of glucokinase in the liver.
d. Muscle synthesizes glycogen in the fed state because glycogen phosphorylase is activated in response to insulin.
e. The plasma concentration of glycogen increases in the fed state.

Answer 26

c. Liver synthesizes more glycogen when the hepatic portal blood concentration of glucose is high because of the activity of glucokinase in the liver.

Question 27

Which one of following statements about glucose metabolism is correct?

Select one:
a. Glucagon increases the rate of glycolysis.
b. Glycolysis requires NADP+.
c. In glycolysis, glucose is cleaved into two three carbon compounds.
d. Substrate level phosphorylation takes place in the electron transport system.
e. The main product of glycolysis in red blood cells is pyruvate.

Answer 27

c. In glycolysis, glucose is cleaved into two three carbon compounds.

Question 28

Which one of following statements about glycogen metabolism is correct?

Select one:
a. Glycogen synthase activity is increased by glucagon.
b. Glycogen phosphorylase is an enzyme that can be activated by phosphorylation of serine residues.
c. Glycogen phosphorylase cannot be activated by calcium ions.
d. cAMP activates glycogen synthesis.
e. Glycogen phosphorylase breaks the α1-4 glycosidic bonds by hydrolysis.

Answer 28

b. Glycogen phosphorylase is an enzyme that can be activated by phosphorylation of serine residues.