Deck 12: Carbohydrate Metabolism: Glycolysis, Gluconeogenesis, Glycogen Metabolism, and the Pentose Phosphate Pathway

Question 1

________ from muscle working anaerobically is released to blood and can be taken up by liver where it is converted to pyruvate by the enzyme lactate dehydrogenase.

Answer 1

Lactate

Question 2

Which of the following types of reaction does NOT occur in glycolysis?

A) Isomerization
B) Nucleophilic attack
C) Aldol condensation
D) Oxidation
E) Dehydration

Answer 2

C

Question 3

Which of the following statements about regulation of phosphofructokinase is FALSE?

A) AMP is an activator.
B) ADP is an activator.
C) Citrate is an inhibitor.
D) Fructose 2,6-bisphosphate is an activator.
E) ATP decreases the apparent Km for fructose-6-phosphate.

Answer 3

E

Question 4

Hexokinase, phosphofructokinase and pyruvate kinase are each subject to ________ control.

Question 5

Flux through the pentose phosphate pathway is controlled mainly by the NADP+/NADPH ratio in the cell.

Question 6

The flux rate through the gluconeogenic pathway is directly proportional to the amount of carbohydrate in the diet.

Question 7

The Pasteur effect describes the observation that yeast-metabolizing glucose anaerobically will dramatically increase their rate of glucose utilization when provided with air.

Question 8

Which of the following cannot be used as a precursor for gluconeogenesis?

A) Glycerol
B) Pyruvate
C) Lactate
D) Leucine
E) Alanine

Question 9

The standard free energy change of the glycolytic pathway to pyruvate is -79.9 kJ/mol, while the standard free energy change associated with gluconeogenesis from pyruvate is -42.7 kJ/mol. What would the standard free energy change be for a direct reversal of the glycolytic pathway.

Question 10

Fructose-1,6-bisphosphate is a feedforward ________ activator of liver pyruvate kinase.

Question 11

Anaerobic glycolysis can produce ATP at a much faster rate than aerobic oxidative phosphorylation.

Question 12

Both glycolysis and gluconeogenesis are controlled by fructose 2,6-bisphosphate in response to hormones.

Question 13

Glycolysis is regulated primarily by:

A) the availability of glucose-6-phosphate.
B) three strongly endergonic, nonequilibrium reactions.
C) three strongly exergonic, nonequilibrium reactions.
D) allosteric effectors of pyruvate kinase.
E) phosphorylation of phosphofructokinase.

Question 14

All of the reactions of both glycolysis and gluconeogenesis occur in the cytosol.

Question 15

Liver pyruvate kinase is activated by dephosphorylation in response to glucagon.

Question 16

Much of the regulation of gluconeogenesis is a result of the inhibition of glycolysis.

Question 17

Pyruvate carboxylase and phosphoenolpyruvate carboxykinase catalyze reactions of gluconeogenesis that bypass the reaction of glycolysis that is catalyzed by ________.

Question 18

The primary gluconeogenic organ in animals is:

A) skeletal muscle.
B) kidney medulla.
C) kidney cortex.
D) liver.
E) heart muscle.

Question 19

Glycogen is a major energy source for skeletal muscle contraction.

Question 20

The oxidation of glucose to lactate has a standard free energy change of approximately -196 kJ/mol. Calculate the efficiency of energy conversion if the standard free energy change for the production of ATP from ADP and inorganic phosphate is +32.2 kJ/mol.

Question 21

The major product from the action of glycogen phosphorylase and the debranching enzyme glucantransferase is ________.

Question 22

Which of the following is NOT involved in glycogen synthesis?

A) UDP-glucose
B) Glycogenin
C) Amylo-(1,4 to 1,6)-transglycosylase
D) Glycogen synthase
E) Glycogen phosphorylase

Question 23

The pentose phosphate pathway provides ________ for reductive biosynthesis and ________ for nucleic acid biosynthesis.

Question 24

Which statement about control of glycogen metabolism is INCORRECT?

A) Epinephrine signals glycogen breakdown in muscle.
B) Glucagon signals glycogen breakdown in liver.
C) Glycogen phosphorylase is activated by phosphorylation.
D) Glycogen synthase is phosphorylated at only one site.
E) Glycogen synthase is activated by dephosphorylation.

Question 25

Phosphorylases and phosphatases catalyze the same reaction, the removal of a phosphate group.

Question 26

Polysaccharide digestion and glycogen breakdown involve sequential cleavage from ________ ends of glucose polymers.