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MFM > Glycogen metabolism > Flashcards

Glycogen metabolism Flashcards

1
Q

where do you find most glycogen stores

A

cytosol of liver and skeletal muscle

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2
Q

how is glucose linked

A

alpha 1,4-glucosidic bond in the main and branched alpha 1,6 linkages

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3
Q

what happens to glucose arising from glycogen breakdown in skeletal and heart muscles

A

remains in the muscle cells and is used to provide energy for muscle work

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4
Q

occurs during fasting and is stimulated by glucagon in liver

A

glycogenolysis

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5
Q

after a meal what enzymes are active

A

glycogen synthase and 4:6 transferase (branching enzyme)

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6
Q

during fasting what enzymes are active

A

debrancher enzyme and glycogen phophorylase

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7
Q

insulin is up, glycogen synthesis active or inactive

A

active

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8
Q

how is futile (energy wasting) controlled during glycogen synthesis

A

breakdown and formation are not active at same time

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9
Q

glycogen synthesis requires

A

ATP and UTP

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10
Q

Glucose 1-P and UTP synthesize

A

UDP-glucose

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11
Q

UDP-glucose adds glucosyl residues to glycogen core (glycogenin) by

A

glycogen synthase

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12
Q

reattaches 6-8 residues in alpha-1,6-bond after chain reaches about 11 residues in length

A

branching enzyme

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13
Q

glycogen synthesis and glycogenolysis are regulated by

A

hormonal changes (insulin and glucagon)

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14
Q

key regulatory enzyme for degradation?

A

glycogen phosphorylase

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15
Q

during fasting _____ elevates in liver

A

glucagon

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16
Q

during exercise, _____ and ____ elevate

A

AMP and epinephrine

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17
Q

____ are partially degraded during exercise or fasting

A

glycogen molecules

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18
Q

glycogen phosphorylase catalyzes the cleavage of ______ bond releasing ______

A

alpha 1,4 glycosidic bond releasing glucose 1-P

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19
Q

hydrolyzes alpha 1,6 glycosidic bond

A

debranching enzyme

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20
Q

glucose 1-P converted to ______ and catabolized for energy in muscle

A

Glucose 6-P

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21
Q

In liver what happens to glucose 1-P

A

converted to glucose 6-P then to glucose by glucose 6-phosphatase and released from the liver as free glucose

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22
Q

glucose 6-phosphatase is found where

A

liver cell’s lumen of ER

23
Q

muscle cells do not need to convert ____ to glucose for usage

A

glucose 6-P

24
Q

liver glycogenesis inhibitors and activators include

A 
- = glucagon, epinephrine, and Ca 2+
\+ = insulin, glucose 6-P
25
Q

liver glycogenolysis inhibitors and activators

A 
- = glucose, insulin, glucose 6-P, ATP
\+ = glucagon, epinephrine, Ca2+
26
Q

muscle glycogenesis inhibitors and activators

A 
- = epinephrine
\+ = insulin, Glc 6-P
27
Q

muscle glycogenolysis inhibitors and activators

A 
- = insulin, Glc-6P, ATP
\+ = epinephrine, AMP, Ca2+
28
Q

insulin binds to what enzyme to dephosphorylate

A

protein phosphatase 1 (PP1)

29
Q

activation of PP1 does what in general and does what to glycogen synthase and phophorylase

A

dephosphorylates

activates glycogen synthase and inactivates glycogen phosphorylase

30
Q

glucagon only affects

A

liver

31
Q

Glucagon does what in liver cells

A
  1. binds G protein coupled receptors on hepatocytes
  2. cAMP from glucagon activated adenylate cyclase increases protein kinase A activity (PKA)
  3. PKA phosphorylates glycogen synthase making it inactive and phosphorylates glycogen phosphorylase making it active
32
Q

muscle glycogen degradation increased with

A

exercise and epinephrine signaling

33
Q

exercise activates muscle glycogenolysis how?

A
  1. muscle contration that produces AMP which is activator of glycogen phosphorylase
  2. nerve signal which increase Ca2+ which binds calmodulin which activates phosphorylase kinase
  3. epinephrine through PKA activates same phosphorylase kinase
34
Q

exercise results in:

A

active glycogen phosphorylase

35
Q

does epinephrine signaling initiate liver glycogen degradation?

A

yes

36
Q

epinephrine binds to what in hepatocytes and what occurs

A

alpha1 adrenergic receptors which are Q’s which activate phospholipase C

37
Q

how does phospholipase C do its job?

A
  1. hydrolyzes PIP2 to DAG and IP3.
  2. IP3 stimulates release of Ca2+ form ER
  3. Ca2+ binds to calmodulin which activates calmodulin-dependent protein kinase and phosphorylase kinase (both Ca2+ and DAG activate PKC)
  4. these 3 kinases phosphorylate glycogen synthase making it inactive. Phosphorylase kinase phosphorylates glycogen phosphorylase making it active
38
Q

how does neonatal hypoglycemia become relevant

A

mother is uncontrolled diabetic

39
Q

who is at most risk for life threatening hypoglycemia?

A

babies that are born prematurely

40
Q

fetal exposure to high levels of glucose results in

A

high glycogen stores and increased insulin levels in fetus

41
Q

______ may develop life threatening hypoglycemia with new borns

A

hyperinsulinemia

42
Q

GSD 1 is called what and what happens with it

A

von Gierke disease
glucose 6-P
severe fasting hypoglycemia, lactic acidosis, hyperuricemia, increase in FA/cholesterol by increase in glucagon signal

43
Q

GSD 2 is called what and what happens with it

A

Pompe disease
Lysosomal alpha glucosidase
leads to cardiac failure and myopathy

44
Q

GSD 3 is called what and what happens with it

A

Cori disease
issue with amylo-1,6-glucosidase (debrancher)
ketolytic hypoglycemia, increase in beta oxidation. glycogen deposits have short outer branches

45
Q

GSD 4 is called what and what happens with it

A

Anderson disease
issue with amylo-4,6-glucosidase (brancher)
hepatosplenomegaly

46
Q

GSD 5 is called what and what happens with it

A

McArdle disease (muscle)
muscle glycogen phosphorylase
exercise induced muscle pains, cramps, and weakness

47
Q

GSD 6 is called what and what happens with it

A

Hers disease (hepatocyte)
liver glycogen phosphorylase
hepatomegaly, good prognosis

48
Q

Pompe disease involves what organ(s)

A

all organs with lysosomes

49
Q

von Gierke disease involves what organ(s)

A

liver

50
Q

Andersens disease involves what organ(s)

A

liver

51
Q

Cori disease involves what organ(s)

A

liver, skeletal muscle, heart

52
Q

McArdle disease involves what organ(s)

A

skeletal muscle

53
Q

Hers disease involves what organ(s)

A

liver (hepatocytes)

MFM (6 decks)

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