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GI I > Glycogen metabolism > Flashcards

Glycogen metabolism Flashcards

1
Q

Where is glycogen mainly found?

A

Liver and muscle

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2
Q

What prevents muscle glycogen from being used as a source of glucose for the body?

A

Lack of glucose-6-phosphatase

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3
Q

What are the major enzymes of glycogenesis?

A

Glycogen synthase
Branching enzyme

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4
Q

What are the two options needed to start the chain of glycogen?

A

UDP-glucose as a primer
Glycogenin

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5
Q

How does the branching enzyme work?

A

Removes 6-8 glucosyl residues from a chain of 10-11 and reattaches it by an alpha(1–>6) linkage

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6
Q

How does G6P become the G1P used in glycogenesis?

A

Phosphoglucomutase

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7
Q

How does G1P become UDP glucose used by glycogen synthase?

A

UDPG pyrophosphorylase using UTP and producing PPi

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8
Q

What are the major enzymes of glycogenolysis?

A

Glycogen phosphorylase
Debranching enzyme

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9
Q

What are the 2 enzymatic subunits of the debranching enzyme?

A

Oligo (1-4) to (1-4) glucan transferase
Amylo (1-6) glucosidase

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10
Q

What is the coenzyme required by glycogen phosphorylase?

A

PLP

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11
Q

How many residues remain before a branch after glycogen phosphorylase is finished?

A

4

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12
Q

What is the main product of glycogenolysis?

A

Glucose-1P

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12
Q

What is the function of the debranching enzyme?

A

Removes three glucosyl residues and reattaches them to main chain.
Cleaves (1-6) bond freeing last glucose-1P

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13
Q

What disease is characterized by accumulation of glycogen in lysosomes?

A

GSD type II - Pompe disease

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14
Q

What is the deficiency seen in Pompe disease?

A

acid maltase deficiency

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15
Q

How does phosphorylation affect glycogen synthase?

A

Inactivates it

16
Q

How does phosphorylation affect glycogen phosphorylase?

A

Activates it

17
Q

How does insulin regulate glycogenesis?

A

Promotes dephosphorylation of glycogen synthase by decreasing cAMP by activating phosphodiesterase

18
Q

How do glucagon and epinephrine inhibit glycogenesis?

A

Promote phosphorylation of glycogen synthase by increasing cAMP by activating adenylate cyclase

19
Q

What promotes glycogenolysis in muscles?

A

Epinephrine only

20
Q

How does calcium influence glycogen metabolism?

A

Released by nerve impulses during muscle contraction. It will bind with calmodulin that activates muscle phosphorylase kinase, thereby activating glycogen phosphorylase

Increases glycogenolysis in muscles

21
Q

What are the inheritances patterns for GSDs I - VI?

A

Autosomal recessive

22
Q

What enzyme is deficient in Von Gierke’s disease (GSD Ia)?

A

Glucose-6-phosphatase

23
Q

What enzyme is deficienct in Cori disease (GSD III)?

A

Debranching enzyme

24
Q

What enzyme is deficient in Anderson disease (GSD IV)?

A

Branching enzyme

25
Q

What enzyme is deficient in McArdle disease (GSD V)?

A

Muscle phosphorylase

26
Q

What enzyme is deficient in Hers’ disease (GSD VI)?

A

Hepatic glycogen phosphorylase

27
Q

What enzyme is deficient in GSD Ib?

A

Glucose-6P translocase

28
Q

What are the signs of Von Gierke’s disease?

A

Hepato- and reno-megaly
Fasting hypoglycemia
Severe lactic acidemia - affects Cori cycle
Ketosis
Hyperlipidemia
Fatty liver
Hyperuricemia

29
Q

What are physical features in children with Von Gierke’s disease?

A

Doll-like face
Protruding abdomen

30
Q

What is the most severe GSD?

A

Pompe disease - type II

31
Q

What are signs of Pompe disease in children?

A

Muscle hypotonia
Muscle weakness
Death from cardiac failure by age 2

32
Q

What are signs of Pompe disease in adults?

A

Muscle dystrophy

33
Q

What are signs of Cori disease?

A

Fasting hypoglycemia
Hepatomegaly in infants
Accumulation of abnormal glycogen with shorter then normal branches

34
Q

What are other names for Cori disease (GSD III)?

A

Forbe disease
Limit dextrinosis

35
Q

What are signs of Anderson disease?

A

Accumulation of abnormal glycogen with few branch points and longer branches
Hepatosplenomegaly
Death from heart or liver failure by 2

36
Q

What are signs of McArdle syndrome?

A

Poor exercise tolerance - muscle cramping and early fatigue
Normal liver enzymes
No rise in blood lactate after exercises
Glycogen with normal structure accumulation in muscles
Myoglobinemia
Myoglobinuria

GI I (19 decks)

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