Deck 24: Glycogen Degradation

Question 1

The hydrolysis catalyzed by α-1,6-glucosidase releases a(n) ______________ molecule.

Answer 1

free glucose

Question 2

______________ markedly stimulates glycogen breakdown in muscle by initiating a cAMP signal-transduction cascade.

Answer 2

epinephrine, adrenalin

Question 3

Which GTP binding protein is activated by epinephrine binding to the adrenergic 7TM receptor?

Answer 3

Gαs

Question 4

Use the following to answer questions
Choose the correct answer from the list below. Not all of the answers will be used.
a) reducing
b) ɑ-1,6-glycosidic
c) phosphorylase kinase
d) ɑ-1,4-glycoside
e) nonreducing
f) phosphorylase a
g) glucose 6-phosphatase
h) UTP-glucose
i) calmodulin
j) phosphorolysis
k) epinephrine
l) glucagon
The ____________ enzyme catalyzes the phosphorylation of glycogen phosphorylase.

Question 5

Use the following to answer questions
Choose the correct answer from the list below. Not all of the answers will be used.
a) reducing
b) ɑ-1,6-glycosidic
c) phosphorylase kinase
d) ɑ-1,4-glycoside
e) nonreducing
f) phosphorylase a
g) glucose 6-phosphatase
h) UTP-glucose
i) calmodulin
j) phosphorolysis
k) epinephrine
l) glucagon
In order to degrade branches in glycogen, two enzymes are required: a transferase and ______________.

Question 6

Use the following to answer questions
Choose the correct answer from the list below. Not all of the answers will be used.
a) reducing
b) ɑ-1,6-glycosidic
c) phosphorylase kinase
d) ɑ-1,4-glycoside
e) nonreducing
f) phosphorylase a
g) glucose 6-phosphatase
h) UTP-glucose
i) calmodulin
j) phosphorolysis
k) epinephrine
l) glucagon
The hormone ____________ signifies the starved state.

Question 7

Use the following to answer questions
Choose the correct answer from the list below. Not all of the answers will be used.
a) reducing
b) ɑ-1,6-glycosidic
c) phosphorylase kinase
d) ɑ-1,4-glycoside
e) nonreducing
f) phosphorylase a
g) glucose 6-phosphatase
h) UTP-glucose
i) calmodulin
j) phosphorolysis
k) epinephrine
l) glucagon
The protein ____________ is the δ subunit of phosphorylase kinase.

Question 8

Use the following to answer questions
Choose the correct answer from the list below. Not all of the answers will be used.
a) reducing
b) ɑ-1,6-glycosidic
c) phosphorylase kinase
d) ɑ-1,4-glycoside
e) nonreducing
f) phosphorylase a
g) glucose 6-phosphatase
h) UTP-glucose
i) calmodulin
j) phosphorolysis
k) epinephrine
l) glucagon
The process by which a bond is cleaved by the addition of orthophosphate is ____________.

Question 9

Use the following to answer questions
Choose the correct answer from the list below. Not all of the answers will be used.
a) reducing
b) ɑ-1,6-glycosidic
c) phosphorylase kinase
d) ɑ-1,4-glycoside
e) nonreducing
f) phosphorylase a
g) glucose 6-phosphatase
h) UTP-glucose
i) calmodulin
j) phosphorolysis
k) epinephrine
l) glucagon
____________: Most of the glucose residues in glycogen are linked by this type of bond.

Question 10

Use the following to answer questions
Choose the correct answer from the list below. Not all of the answers will be used.
a) reducing
b) ɑ-1,6-glycosidic
c) phosphorylase kinase
d) ɑ-1,4-glycoside
e) nonreducing
f) phosphorylase a
g) glucose 6-phosphatase
h) UTP-glucose
i) calmodulin
j) phosphorolysis
k) epinephrine
l) glucagon
The ____________ enzyme serves as the glucose "sensor" enzyme in liver cells.

Question 11

Use the following to answer questions
Choose the correct answer from the list below. Not all of the answers will be used.
a) reducing
b) ɑ-1,6-glycosidic
c) phosphorylase kinase
d) ɑ-1,4-glycoside
e) nonreducing
f) phosphorylase a
g) glucose 6-phosphatase
h) UTP-glucose
i) calmodulin
j) phosphorolysis
k) epinephrine
l) glucagon
____________ takes place instead of hydrolysis in glycogen breakdown.

Question 12

Use the following to answer questions
Choose the correct answer from the list below. Not all of the answers will be used.
a) reducing
b) ɑ-1,6-glycosidic
c) phosphorylase kinase
d) ɑ-1,4-glycoside
e) nonreducing
f) phosphorylase a
g) glucose 6-phosphatase
h) UTP-glucose
i) calmodulin
j) phosphorolysis
k) epinephrine
l) glucagon
____________ is the liver enzyme that cleaves the phosphate from glucose 6-phosphate.

Question 13

Use the following to answer questions
Choose the correct answer from the list below. Not all of the answers will be used.
a) reducing
b) ɑ-1,6-glycosidic
c) phosphorylase kinase
d) ɑ-1,4-glycoside
e) nonreducing
f) phosphorylase a
g) glucose 6-phosphatase
h) UTP-glucose
i) calmodulin
j) phosphorolysis
k) epinephrine
l) glucagon
In skeletal muscle, the binding of ______________ stabilizes phosphorylation b into the active form.

Question 14

Use the following to answer questions
Choose the correct answer from the list below. Not all of the answers will be used.
a) reducing
b) ɑ-1,6-glycosidic
c) phosphorylase kinase
d) ɑ-1,4-glycoside
e) nonreducing
f) phosphorylase a
g) glucose 6-phosphatase
h) UTP-glucose
i) calmodulin
j) phosphorolysis
k) epinephrine
l) glucagon
Phosphoglucomutase requires the intermediate ______________ for the interconversion of glucose 1-phosphate and glucose 6-phosphate.

Question 15

The transferase enzyme shifts a block of ______________ glycosyl units.

Question 16

In the liver, glycogen synthesis and degradation are regulated to maintain levels of ______________ in the blood.

Question 17

One mechanism for turning off glycogen degradation involves the removal of a phosphate group from glycogen phorphorylase by the enzyme ____________.

Question 18

Use the following to answer questions
Choose the correct answer from the list below. Not all of the answers will be used.
a) reducing
b) ɑ-1,6-glycosidic
c) phosphorylase kinase
d) ɑ-1,4-glycoside
e) nonreducing
f) phosphorylase a
g) glucose 6-phosphatase
h) UTP-glucose
i) calmodulin
j) phosphorolysis
k) epinephrine
l) glucagon
____________ is the end of glycogen where interconversion between the open and closed conformation of the anomeric carbon is possible

Question 19

Use the following to answer questions
Choose the correct answer from the list below. Not all of the answers will be used.
a) reducing
b) ɑ-1,6-glycosidic
c) phosphorylase kinase
d) ɑ-1,4-glycoside
e) nonreducing
f) phosphorylase a
g) glucose 6-phosphatase
h) UTP-glucose
i) calmodulin
j) phosphorolysis
k) epinephrine
l) glucagon
The type of bond that is located at the branch points in glycogen is ____________.

Question 20

Phosphorylase kinase becomes fully active by being phosphorylated and binding ___________.

Question 21

The major site(s) of glycogen storage is (are):

A) adipose tissue.
B) liver.
C) skeletal muscle.
D) B and C.
E) A, B, and C.

Question 22

Which molecule(s) must be excluded from the active site of glycogen phosphorylase?

A) glucose
B) glucose 1-phosphate
C) water
D) All of the above.
E) None of the above.

Question 23

Why does the liver possess a specific enzyme that can cleave glucose 6-phosphate to form glucose and orthophosphate?

Question 24

What are some of the advantages of having glycogen as a readily available glucose source?

Question 25

What physiological conditions render phosphorylase b less active?

A) high ATP, high AMP, and glucose 6-phosphate levels
B) high ATP and low calcium ion levels
C) high ATP and high glucose 6-phosphate levels
D) All of the above.
E) None of the above.

Question 26

Muscle phosphorylase is mostly inactive when:

A) the enzyme is in the b conformation
B) in the R state.
C) bound to AMP.
D) All of the above.
E) None of the above.

Question 27

Two critical hormones that signal for glycogen breakdown are:

A) insulin and epinephrine.
B) glucagon and epinephrine.
C) glucagon and insulin.
D) All of the above.
E) None of the above.

Question 28

Why is the formation of glucose 1-phosphate advantageous?

Question 29

What is required to remove branches in glycogen?

A) a debranching enzyme
B) a transferase enzyme
C) a glycosidase enzyme.
D) A and C
E) All of the above.

Question 30

Draw a structure showing the most common linkage between glucose units found in glycogen.

Question 31

Why is the T state of glycogen phosphorylase less active?

A) The adjacent amino acids are not phosphorylated; thus the catalysis cannot be carried out.
B) The active site is partially blocked.
C) ATP cannot be bound by the T state.
D) All of the above.
E) None of the above.

Question 32

Why must glycogen control be manifested differently in muscle and liver?

Question 33

Which liver enzyme is deficient in Hers disease?

A) phosphorylase
B) transferase
C) glucosidase
D) phosphoglucomutase
E) None of the above.

Question 34

The key enzyme in glycogen degradation is:

A) glycogen phosphatase.
B) glycogen phosphorylase.
C) glucose 1-phosphate synthase.
D) All of the above.
E) None of the above.

Question 35

What is the function of liver glycogen degradation?

A) to export glucose to other tissues when glucose levels are low
B) to maintain glucose levels after a large meal
C) to provide for the large energy needs of the liver
D) All of the above.
E) None of the above.

Question 36

Why can't the glucose 1-phosphate diffuse out of the cell?

Question 37

What are the three steps in glycogen degradation?

Question 38

Conversion of glucose 1-phosphate to glucose 6-phosphate is carried out by the enzyme:

A) phosphoglucomutase.
B) kinase 1-P.
C) phosphoglycerate mutase.
D) All of the above.
E) None of the above.

Question 39

Calcium binds and leads to the activation of which enzyme in glycogen degradation?

A) phosphorylase
B) phosphoglucomutase
C) protein kinase C
D) phosphorylase kinase
E) glycogen phosphorylase

Question 40

How is phosphorylase b converted into phosphorylase a?

A) through the addition of a phosphate to a serine residue
B) through dimerization, which forms the active-site pocket
C) through cleavage of 10 amino acids from the N-terminal end of the protein
D) All of the above.
E) None of the above.

Question 41

What path, in addition to the cAMP-induced signal transduction, is used in the liver to stimulate glycogen breakdown by epinephrine?

Question 42

What are the two regulatory controls for phosphorylase kinase?

Question 43

Phosphorylase a and b both exist in equilibrium between R and T states. Which are the most active and least active combinations?

Question 44

How does epinephrine stimulate glycogen breakdown in muscle? (Describe the series of events.)