chapter 24

Question 1

1 glycogen contains how many glucose residues

Answer 1

55,000

Question 2

glycogen phosphorylase degrades glycogen from

Answer 2

the non-reducing ends of the molecule

Question 3

glycogen phosphorylase catalyzes a reaction that yields

Answer 3

glucose-1-phosphate

Question 4

glucose-1-phosphate is converted into

Answer 4

glucose 6-phosphate

Question 5

what does phosphoglucomutase do

Answer 5

converts glucose-1-phosphate to glucose 6-phosphate

Question 6

glycogen phosphorylase can only cleave

Answer 6

a-1,4-glycosidic bonds

Question 7

glycogen phosphorylase can not cleave

Answer 7

near branch points

Question 8

what does the transferase do

Answer 8

shifts a small oligosaccharide near the branch point to a nearby chain, removing the branch and making this accessible for the phosphorylase

Question 9

what does the debranching enzyme do

Answer 9

cleaves the a-1,6 bond at the branch point, releasing a free glucose

Question 10

what amino acid is phosphorylated at the active site of phosphoglucomutase

Answer 10

serine

Question 11

what does glucose-6- phosphatase do in the liver

Answer 11

generates a free glucose that is then released into the blood for use by other tissues such as the brain and red blood cells

Question 12

what is the key regulatory enzyme for glycogen degredation

Answer 12

glycogen phosphorylase

Question 13

what are the two states of the phosphorylase

Answer 13

R state and T state

Question 14

what are the two forms of the phosphorylase

Answer 14

a and b form

Question 15

how does the a form differ from the b form

Answer 15

the serine residue is phosphorylated

Question 16

what state is favored in the b form

Answer 16

the t state

Question 17

what state is favored in the a form

Answer 17

the r state

Question 18

what is the default form and state of the liver

Answer 18

the a form in the R state

Question 19

what does the default state of the liver mean in simpler terms

Answer 19

liver phosphorylase is prepared to generate blood glucose unless signaled otherwise

Question 20

what kind of regulator is glucose

Answer 20

a negative regulator because it facilitates the transformation from the r state to the t state

Question 21

what is the default form and state of phosphorylase in muscle

Answer 21

b form in the t state

Question 22

what stabilizes the r state in muscle

Answer 22

the phosphorylase binds AMP

Question 23

what stabilizes the t state in muscle

Answer 23

ATP and glucose 6-phosphate

Question 24

what does phosphorylase kinase do

Answer 24

converts glycogen phosphorylase b to phosphorylase a with the addition of a phosphate

Question 25

what does the conversion from phosphorylase b to a do

Answer 25

makes the enzyme more active

Question 26

what activates phosphorylase kinase

Answer 26

phosphorylation and calcium ions

Question 27

what transmits the signal for glycogen breakdown

Answer 27

G proteins

Question 28

how is glycogen degradation turned off

Answer 28

1. hormones that stimulate glycogen breakdown are no longer present
2. inherent GTPase activity of the Ga subunit inactivates G protein signaling
3. phosphodiesterase converts cAMP into AMP, which does not stimulate protein kinase A
4. protein phosphatase 1 removes phosphoryl groups from phosphorylase kinase and glycogen phosphorylase, inactivating the enzymes