Metabolism 05 - Glycogen

Question 1

what are the two tissues that have highest amount of glycogen?

Answer 1

Muscle glycogen, liver glycogen

Question 2

Different roles of muscle vs liver glycogen

Answer 2

liver provides for body

muscle provides for muscle

Question 3

What will happen if there is impaired hepatic muscle glycogen degradation on blood glucose levels?

Answer 3

Blood glucose levels will plummet during fasting periods

Question 4

What will happen if there is impaired muscle glycogen degradation on glucose levels and on abiility to exercise

Answer 4

There is impaired glucose levels in the cell itself but not body wide; ability to exercise will be severely impaired

Question 5

Impact of impaired liver or muscle glycogen degradation on the concentration of glycogen in that tissue?

Answer 5

Glycogen will build up

Question 6

glycogen synthase and branching enzyme

Answer 6

Synthase- adds glucose in alpha 1,4 straight line units

branching - adds glucose at a branch point 1,6 linkage

Question 7

Enzymes required to break down glycogen

Answer 7

Debranching enzyme
transferases
glycogen phosphorylase
glucose 6 phosphatase

Question 8

Glycogen phosphorylase is active when (phosphorylated, unphosphoryalted)

Answer 8

phosphorylated

Question 9

When will glycogen phosphorylase be active? What is the protein involved?

Answer 9

When phosphorylase kinase phosphorylates the glycogen phosphorylase

Question 10

What hormone prevents glycogen phosphorylase kinase from activating glycogen phosphorylase?

Answer 10

insulin

Question 11

When is the phosphorylase kinase active (what covalent modification is or is not present)

Answer 11

must be phosphorylated

Question 12

activating factors for phosphorylase kinase

Answer 12

cyclic AMP , calcium

Question 13

What proteins will make the phosphorylase kinase for glycogen phosphorylase active?

Answer 13

glucagon and epinephrine

Question 14

Can insulin have a direct effect on the phosphoprotein phosphatase for glycogen phosphorylase?

Answer 14

Yes, it will activate it (allosteric effect); cAMP can deactivate it (also allosteric)

Question 15

AMP effect on glycogen phosphorylase

Answer 15

can override the unactivated form to activate it

Question 16

Glucose and ATP affect on glycogen phosphorylase

Answer 16

Can override the activated form to deactivate it

Question 17

Glycogen synthase is active when (phosphorylated, dephosphorylated)

Answer 17

dephosphorylated

Question 18

3 second messenger systems involved in regulation of glycogen metabolism

Answer 18

IP3/DAG, Ca, cAMP (also insulin –> GSK3)

Question 19

Reciprocal regulation of glycogen syntahse and glycogen phosphorylase at the level of the second messenger systems and hormonal systems

Answer 19

Phosphorylation events are going to be reciprocal so that insulin will activate the synthase and inhibit the phosphorylase for example, and glucagon and epinephrine will have the opposite overall effect.

Question 20

What will elevated glucose 6 phosphate do to glycogen synthesis?

Answer 20

Promote glycogen synthesis by overriding the inhibited state of glycogen synthase

Question 21

What will elevated AMP do to glycogen synthesis

Answer 21

Inhibit glycogen synthesis / promote breakdown

Question 22

Type 1 glycogen storage disease (von gierke)

Answer 22

Glucose 6 phosphatase deficiency, happens in liver and kidney –> enlarged glycogen and normal structure, individuals have enlarged liver, failure to thrive, severe hypoglycermia, hyperuricemia, hyperlipidemia, cognitive deficits

Question 23

Type II glycogen storage disease (Pompe)

Answer 23

1,4 glucosidase (lysosomal) is fucked – happens to affect all organs, get massive increase in glycogen of nomal structure and end up with cardiorespiratory failure,d eath, hypotonia and cardiomegaly

Question 24

Type III glycogen storage disease (Cori’s disease)

Answer 24

Amylo 1,6 debranching enzyme fucked, happens in muscle and liver, increased short outer glycogen appearance, this is like type I but milder

Question 25

Type IV glycogen storage disease (Anderson’s disease)

Answer 25

Branching enzyme is fucked
Happens in liver and spleen
Glycogen is in normal quantities but has long branches
Progressive cirrhosis of the liver, liver failure cuauses death before age 2

Question 26

Type V glycogen storage disease (McArdle)

Answer 26

Phosphorylase is fucked, happens in muscle
Glycogen is in moderate amount, but with normal structure. However there is limited ability to perform strenuous exercise, and painful muscle cramps

Question 27

Type VI glycogen storage disease (Hers’ Disease)

Answer 27

Phosphorylase is fucked, happens in liver
Glycogen is in increased amount
this is like tpe I (enlarged liver, fialure to thrive, hypoglycemia and hyperuricemia, hyperlipidemia, cognitive deficits) but milder

Question 28

Glycogen storage disease type VII

Answer 28

PFK1 is fucked up
happens in muscle
increased amount of glycogen
limited ability to perform strenuous exercise and painful muscle cramps

Question 29

Glycogen storage disease type VIII

Answer 29

phosphorylase kinase is fucked, liver is location
increased amount of glycogen, normal morphology
Mild liver enlargement, mild hypoglycemia

Question 30

Glycogen storage disease type 0

Answer 30

Glycogen synthase is fucked, happens in liver
glycogen is decreased
hypoglycemia, postprandial lactic acidemia, fasting ketosis

Question 31

Glucagon and epinephrine promote homeostasis in what 6 ways?

Answer 31

1. raise blood glucose levels
2. promote hepatic gluconeogenesis
3. promote hepatic glycogen degradation
4. block hepatic utilization of glucose
5. inhibit hepatic glycolysis
6. inhibit hepatic glycogen synthesis

Question 32

Glucagon and epinephrine inhibit hepatic glycolysis by affecting what enzymes

Answer 32

Inhibit PFK2 so you do not get F26BP – therefore this blocks PFK1 indirectly
Inhibit pyruvate kinase directly

Question 33

Ribose 5 phosphate is important for what?

Answer 33

DNA and RNA synthesis

Question 34

Pentose phosphate pathway generates what 2 important intermediates

Answer 34

NADPH

Ribose 5 phosphate

Question 35

Rate limiting enzyme in pentose phosphate pathway

Answer 35

Glucose 6 phosphate dehydrogense

Question 36

potential uses of NADPH

Answer 36

Relief of oxidative damage – glutathione uses NADH to get back to reduced state so it can handle oxidative stress