Lecture 26 - Glycogen Metabolism I Flashcards
(19 cards)
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
D. A non-reducing -OH at C4
The reducing, or C1, end of the glucose monomer is attached to what protein?
Glyocogenin (“generates glycogen)
The ____ is manufactured by glycogenin and is important in adding long chains to the core.
primer
What co-factor is required for glycogenin function? A. Co B. Fe C. Mg D. Mn
D. Mn (manganese)
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
A. Liver glycogen is in the “a,” phosphorylated active form and maintains basal BGL
Cleaves glucose-1-P from glycogen A. Glycogen phosphorylase B. Phosphoglucomutase C. Glucose-6-Phosphatase D. Enolase
A Glycogen phosphorylase
What co-factors if required for glycogen phosphorylase?
Pyridoxyl phosphate (Vit. B6)
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
a. alpha-1,6 branch point
Cleaves 3 of 4 glucose molecules before a-1,6 branch point.
a. hexokinase
b. glycogen phosphorylase
c. transferase
d. glucokinase
c. transferase (moves them to end of non-reducing end of main chain, forming a new a-1,4 bond)
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
D. debranching (“a-1,6 glucosidase”) enzyme
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.
A. G-6-P; phosphoglucomutase
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
A. Long chains of a-1,4 glucose with a-1,6 branch points
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
C. inactivated/changed to T-state
Inactivation of GP by high glucose levels causes a(n) (decrease/increase) in glycogen breakdown.
decrease; high BGL = no need to cleave glycogen
ATP and G-6-P cause a switch in muscle glycogen phosphorylase to the ___ form.
inactive “b” form, no need to cleave glycogen
Phosphorylation of ____ residue converts glycogen phosphorylase to the active form.
serine
Conversion of GP from the ‘b’ to phosphorylated “a” form is carried out by _____.
A. GSK
B. PK
C. PP1
D. GPK
B. Phosphorylase kinase - adds a Pi to glycogen phosphorylase
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
A. By phosphorylase kinase
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
D. Phosphorylation by PKA
