Question 1

In gluconeogenesis, the initial reaction converts pyruvate to

Accepted Answer

A)   oxaloacetate
B)   acetyl-CoA
C)   phosphoenolpyruvate
D)   lactate
E)   glucose A

Question 2

The activity of glycogen phosphorylase depends on

Accepted Answer

A)   allosteric control
B)   covalent modification
C)   both of these
D)   neither of these C

Question 3

Glycolysis that starts with glycogen instead of glucose can be considered to have a higher energy yield because:

Accepted Answer

A)   Phosphorolysis reactions cleave bonds with phosphate instead of water.
B)   Phosphorylase is a better enzyme than hexokinase
C)   Phosphorylase produces a glucose phosphate without spending an ATP to do it
D)   All of these
E)   None of these is true because glycolysis starting from glycogen does not have a higher energy yield C

Question 4

What is the average chain length of the branches in glycogen?

Accepted Answer

A)   6 glucose residues
B)   13 glucose residues
C)   25 glucose residues
D)   50 glucose residues
E)   100 glucose residues

Question 5

UDP-glucose pyrophosphorylase works by this mechanism:

Accepted Answer

A)   It adds a phosphate group to glucose from UTP, leaving behind UDP.
B)   It adds a UMP molecule to glucose-1-phosphate by splitting out pyrophosphate.
C)   It adds a pyrophosphate group to glucose, using UTP.
D)   It adds a UDP molecule to glucose by splitting out phosphate.
E)   None of these

Question 6

The regulatory enzymes in gluconeogenesis are

Accepted Answer

A)   hexokinase, phosphofructokinase, and pyruvate kinase
B)   glucose-6-kinase, aldolase, and enolase
C)   glucose-6-phosphatase, fructose-1,6-bisphosphatase, pyruvate carboxylase, and phosphoenolpyruvate carboxykinase
D)   pyruvate carboxylase, aldolase, and phosphofructokinase

Question 7

Glycogen phosphorylase

Accepted Answer

A)   exists in two forms, phosphorylase a and phosphorylase b
B)   responds differently to allosteric effectors in its phosphorylated and dephosphorylated forms
C)   both of these
D)   neither of these

Question 8

Which enzyme cleaves the α(1 → 6) bonds in glycogen?

Accepted Answer

A)   glycogen phosphorylase
B)   debranching enzyme
C)   phosphoglucomutase
D)   glycogen synthase
E)   None of these because there are no α(1 → 6)  bonds in glycogen.

Question 9

Which of the following best describes how liver supplies other tissues with the glucose it releases from its stored glycogen?

Accepted Answer

A)   It releases short chains of glucose residues into the blood.
B)   It releases glucose-1-phosphate into the blood.
C)   It releases glucose-6-phosphate into the blood.
D)   It releases glucose into the blood.
E)   It releases glucose in the form of lipopolysaccharides

Question 10

When glycogen phosphorylase is phosphorylated

Accepted Answer

A)   its activity decreases.
B)   its activity increases.
C)   its activity is unaffected.
D)   none of these because that enzyme doesn't get phosphorylated.

Question 11

What kind of reaction is used to release glucose units from glycogen?

Accepted Answer

A)   hydrolysis
B)   phosphorolysis
C)   dehydration
D)   oxidation
E)   dehydrogenation

Question 12

High concentrations of fructose-2,6-bisphopshate

Accepted Answer

A)   stimulate glycolysis and inhibit gluconeogenesis.
B)   inhibit glycolysis and stimulate gluconeogenesis.
C)   stimulate both glycolysis and gluconeogenesis.
D)   inhibit both glycolysis and gluconeogenesis.
E)   none of these

Question 13

In one normal cycle of the pentose phosphate pathway, the enzyme transaldolase is used twice and the enzyme transketolase is used once.

Accepted Answer

A) True 
 B)False

Question 14

The molecule fructose 2,6-bisphosphate:

Accepted Answer

A)   is an intermediate in glycolysis
B)   is an intermediate of gluconeogenesis but not glycolysis
C)   does not exist
D)   is an important regulatory molecule in the control of carbohydrate metabolism
E)   none of these

Question 15

Hydrolysis of pyrophosphate is an important energy driving force in the synthesis of glycogen.

Accepted Answer

A) True 
 B)False

Question 16

Which nucleotide triphosphate is hydrolyzed in the conversion of oxaloacetate to phosphoenolpyruvate?

Accepted Answer

A)   ATP
B)   GTP
C)   CTP
D)   UTP
E)   No nucleotide triphosphate is hydrolysed.

Question 17

The formation and breakdown of fructose 2,6-bisphosphate

Accepted Answer

A)   is catalyzed by the same protein dependant upon whether it is phosphorylated or not.
B)   is catalyzed by the same protein dependant allosteric regulators.
C)   is catalyzed by different proteins.
D)   none of these

Question 18

In which cellular compartment is pyruvate carboxylase found?

Accepted Answer

A)   cytosol
B)   mitochondria
C)   endoplasmic reticulum
D)   nucleus

Question 19

Which of the following occurs when insulin is released?

Accepted Answer

A)   insulin binds to receptors on cell surfaces
B)   a protein kinase cascade is begun that leads to glycogen synthesis
C)   insulin stimulates the GLUT4 transport protein system in muscle cells
D)   glucose transporters move glucose out of the blood and into the cell
E)   all of these

Question 20

Which of the following happens when epinephrine and glucagon are released

Accepted Answer

A)   glycogen phosophorylase is activated and glycogen synthase is inhibited
B)   glycogen phosphorylase and glycogen synthase are activated
C)   glycogen phosphorylase and glycogen synthase are inhibited
D)   glycogen phosphorylase is inhibited and glycogen synthase is activated
E)   none of these

Exam 18: Storage Mechanisms and Control in Carbohydrate Metabolism