Lecture 26 - Glycogen Metabolism I

Question 1

The terminal glucose contains what characteristic feature?
A. A reducing -OH end at C3
B. A reducing -OH and C4
C. A non-reducing -OH at C3
D. A non-reducing -OH at C4

Answer 1

D. A non-reducing -OH at C4

Question 2

The reducing, or C1, end of the glucose monomer is attached to what protein?

Answer 2

Glyocogenin (“generates glycogen)

Question 3

The ____ is manufactured by glycogenin and is important in adding long chains to the core.

Answer 3

primer

Question 4

What co-factor is required for glycogenin function?
A. Co
B. Fe
C. Mg
D. Mn

Answer 4

D. Mn (manganese)

Question 5

What key difference in in function is present between muscle glycogen and liver glycogen in humans?

A. Liver glycogen is in the “a,” phosphorylated active form and maintains basal BGL
B. Liver glycogen is in the “b,” dephosphorylated inactive form and responds only to low BGL

Answer 5

A. Liver glycogen is in the “a,” phosphorylated active form and maintains basal BGL

Question 6

Cleaves glucose-1-P from glycogen
A. Glycogen phosphorylase
B. Phosphoglucomutase
C. Glucose-6-Phosphatase
D. Enolase

Answer 6

A Glycogen phosphorylase

Question 7

What co-factors if required for glycogen phosphorylase?

Answer 7

Pyridoxyl phosphate (Vit. B6)

Question 8

Phosphorlysis of glycogen occurs until _____ point.

a. a-1,6 branch point
b. b-1,6 branch point
c. a-2,6 branch point
d. a-2,6 branch point

Answer 8

a. alpha-1,6 branch point

Question 9

Cleaves 3 of 4 glucose molecules before a-1,6 branch point.

a. hexokinase
b. glycogen phosphorylase
c. transferase
d. glucokinase

Answer 9

c. transferase (moves them to end of non-reducing end of main chain, forming a new a-1,4 bond)

Question 10

Cleaves remaining glucose after transferase removes 3 glucose prior to a-1,6 branch point.

a. transferase
b. glucokinase
c. hexokinase
d. debranching (“a-1,6 glucosidase”) enzyme

Answer 10

D. debranching (“a-1,6 glucosidase”) enzyme

Question 11

Cleaved glucose-1-P is changed to \_\_\_ by \_\_\_\_\_, allowing it to be further processed.
A. G-6-P; phosphoglucomutase
B. 3-GP; phosphoenolase
C. DHAP; triose aldehyde isomerase
D.

Answer 11

A. G-6-P; phosphoglucomutase

Question 12

Describe the overall structure of glycogen.
A. Long chains of a-1,4 glucose with branch points of a-1,6
B. Long chains of a-1,6 glucose with branch points of a-1,4
C. Long chains of B-1,4 glucose with branch points of a-1,4

Answer 12

A. Long chains of a-1,4 glucose with a-1,6 branch points

Question 13

Liver glycogen phosphorylase is \_\_\_\_\_\_ by addition of glucose during high energy states.
A. inactivated/changed to R-state
B. activated/changed to T-state
C. inactivated/changed to T-state
D. activated/changed to R-state

Answer 13

C. inactivated/changed to T-state

Question 14

Inactivation of GP by high glucose levels causes a(n) (decrease/increase) in glycogen breakdown.

Answer 14

decrease; high BGL = no need to cleave glycogen

Question 15

ATP and G-6-P cause a switch in muscle glycogen phosphorylase to the ___ form.

Answer 15

inactive “b” form, no need to cleave glycogen

Question 16

Phosphorylation of ____ residue converts glycogen phosphorylase to the active form.

Answer 16

serine

Question 17

Conversion of GP from the ‘b’ to phosphorylated “a” form is carried out by _____.

A. GSK
B. PK
C. PP1
D. GPK

Answer 17

B. Phosphorylase kinase - adds a Pi to glycogen phosphorylase

Question 18

Epinephrine is secreted by active muscle, and glucagon is released in response to low BGL. Through second messenger systems, how is glycogen phosphorylase DIRECTLY activated?

A. By phosphorylase kinase
B. By production of cAMP from adenylate cyclase
C. By protein kinase A
D. By dimerization of the adrenergic receptor

Answer 18

A. By phosphorylase kinase

Question 19

PK is important in the activation of GP. In addition to Ca2+, what other step is important in activation of PK?

A. Conversion of GP to the T-form
B. Addition of another co-factor
C. Dephosphorylation by PP1
D. Phosphorylation by PKA

Answer 19

D. Phosphorylation by PKA