Chapter 9.5

Question 1

Where is glycogen stored in cells

Answer 1

• it is stored in the cytoplasm in granules
• if it is linear and not branched
• > then there is the highest density of glucose in glycogen near the core of the granule
• if it is branched
• > then there is the highest density of glucose in glycogen near the periphery of the granule
• > being in the periphery allows for more rapid release of glucose

Question 2

What is the difference between glycogen stored in the liver and that stored in the muscle

Answer 2

Liver

• > used as a source of glucose
• > used between meals to prevent low glucose levels

Muscle
->used for muscle contraction

Question 3

What is the rate limiting step in glycogen synthesis

Answer 3

-glycogen synthase is the rate-limiting enzyme of glycogen synthesis

Question 4

What is the function of glycogen synthase

Answer 4

• it forms the alpha-1,4-glycosidic bonds found in linerar glucose chains of the granule
• > stimulated by glucose-6-phosphate and insulin
• > inhibited by epinepherine and glucagon

Question 5

What is the purpose of the branching enzyme

Answer 5

• it hydrolyzes one of the alpha-1,4-glycosidic bonds to release a block of oligoglucose
• > then forms an alpha-1,6 bond to create a branch

Question 6

What is the rate-limiting enzyme of glycogenolysis

Answer 6

• it is glycogen phosphorylase

- >forms glucose-1-phosphate

Question 7

What is the glycogen phosphorylase activated and inhibited by

Answer 7

• it is activated by glucagon in the liver, epinepherine/AMP in skeletal muscle
• > it is inhibited by ATP

Question 8

What are glycogen store diseases. What is the result of this disease?

Answer 8

• when different isoforms of the glycogen enzymes are present
• > this results in accumulation or a lack of glycogen in one or more tissues

Question 9

What does glycogenesis begin with

Answer 9

-it begins with a core protein called glycogenin

Question 10

How is phosphorylase different from hydrolase

Answer 10

• phosphorylase breaks bonds using an inorganic phosphate instead of water
• hydrolase uses water to break bonds

Question 11

What are debranching enzymes process

Answer 11

• breaks an alpha 1,4 bond adjacent to the branch point and moves the small oligoglucose chain that is released to the exposed chain at the other end
• forms a new alpha 1, 4 bond
• then the last step is hydrolyzation of a alpha-1,6 bond, releasing a single residue at the branch point as free glucose