Glycogen Catabolism

Question 1

What is glycogen ?

Answer 1

A storage polysaccharide.
A very large polymer of glucose (alpha 1-4) and (alpha 1-6 linkage)
55,000 glucose residues - developing large alpha rosettes of glycogen granules

Question 2

Who made major discoveries on glycogen metabolism?

Answer 2

The Coris

Question 3

Where are large alpha rosettes found?

Answer 3

In the liver and in muscle cells.

Question 4

What does glycogen do?

Answer 4

• stored during meals ‘metered out’ during day.
• mobilised storage form of glucose.
• controlling blood glucose

Question 5

What is the main catabolic enzyme in glycogen catabolism?

Answer 5

Glycogen phosphorylase - very highly regulated.

Question 6

What is the role of glycogen phosphorylase enzyme?

Answer 6

It removes the terminal glucose residues from non-reducing end by phosphorolysis.
Adds a phosphoryl group.
Creates lots of glucose 1-phosphate.

Question 7

Describe the debranching enzyme in the role of glycogen catabolism?

Answer 7

Glycogen phosphorylase acts until it meets the alpha 1-6 branch and stops working 4 residues before end.
Transferase activity - ‘debranching enzyme’ removes 3 glucose residues before branch to another tier.
Alpha 1-6 glucosidase activity of debranching enzyme cuts off glucose and continues on branch,

Question 8

What is the final product of glycogen catabolism?

Answer 8

Lots of glucose 1 - phosphate which phosphoglucomutase converts to glucose 6-phosphate.

Question 9

Describe the role of glucose 6-phosphate to becoming energy in the body/glycolysis? In liver?

Answer 9

In liver = glucose 6-phosphatase
Becomes glucose - blood
Transports to tissues = glycolysis.

Question 10

Describe the role of glucose 6-phosphate to becoming energy in the body/glycolysis? In the muscle cells?

Answer 10

In muscle = glycolysis step 2 (anaerobic/aerobic)

= energy

Question 11

What is the test for newborns for metabolic diseases?

Answer 11

The heel prick test, tests for rare usually inherited in autosomal recessive manner.

Question 12

What are the 3 enzymes in which genetic mutations occur in glycogen storage?

Answer 12

glycogen phosphorylase
glycogen debranching enzyme
glycogen 6-phosphatase

Question 13

What are some of the results and treatments for glycogen storage diseases?

Answer 13

big liver, myopathy, metabolic problems.

Treatment = low glucose/monitored carb diet.