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S3B2 Biochemistry > Glycogen Metabolism > Flashcards

Glycogen Metabolism Flashcards

1
Q

What is the bonding / branching pattern of lycogen?

A

storage form of carbohydrates in animals

alpha 1-4 glucose w/ alpha 1-6 branches

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2
Q

Where is glycogen found & what is its respective function in each of those places?

A
  • liver (and kidney)
    • provide glucose for circulation to other tissues
  • skeletal muscle & heart
    • provide glucose for muscle use
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3
Q

What enzyme adds new glucosyl residues to glycogen?

A

glycogen synthase

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4
Q

What primer is required for glycogen synthesis?

A

glycogenin

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5
Q

What enzyme adds branch points to glycogen?

A

branching enzyne

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6
Q

How are glycosyl residues added to glycogen?

A

one at a time to non-reducing end

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7
Q

In what form can glucose be added to glycogen?

How is this form produced?

A

UDP-glucose (activated glucose)

  • Glu-6-P –> Glu-1-P
    • phosphoglucomutase
  • glu-1-P + UTP –> UDP-glucose
    • UDP-glucose pyrophosphorylase
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8
Q

Whta is the numerical pattern for glycogenesis branch points?

A
  • occurs after a minimum of 11 glycosyl residues have been added
  • the terminal 6-7 are removed as a block & moved to a more interior site
    • attached by alpha 1-6 linkage
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9
Q

How are glucose units removed from glycogen?

This process requires what cofactor?

A

removed one residue at a time from a non-reducing end of glycogen by glycogen phosphorylase

Requires pyridoxical phosphate

hydrolytic reaction – yields glucose NOT glu-P

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10
Q

Pyridoxical phosphate is a derivative of what vitamin?

A

vitamin B6

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11
Q

What enzymes are involved with glycogenolysis?

A
  • Phosphorylase removes glycosyl residues until 4 units remain behind a branch point
  • Debranching enzyme moves a triose from branch point to another branch
    • contains alpha 1-6 glucosidase activity (removes branched glucosyl residue)
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12
Q

What enzymes are reciprocally active due to the tightly regulated & coordinately controlled processes of glycogenesis and glycogenolysis?

A

glycogen synthase

phosphorylase

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13
Q

What hormones exert regulatory contorl over glycogen metabolism?

What are their effects?

A
  • Insulin
    • stimulates glycogenesis
    • inhibits glycogenolysis in liver + muscle
  • Glucagon
    • inhibits glycogenesis
    • stimulates glycogenolysis in liver
  • Epinephrine
    • stimulates glycogenolysis in liver and muscle
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14
Q

What are the two forms of glycogen phosphorylase & what is their differentiating factor?

A
  • phosphorylase-a
    • phosphoryated
    • active
  • phosphorylase-b
    • dephosphorylated
    • inactive
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15
Q

Phosphorylation of glycogen phosphorylase is controlled by what enzyme?

How is it regulated?

A

phosphorylase kinase

activated by Ca2+ & subsequent phosphorylation

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16
Q

What enzyme removes the phosphate from the glycogen phosphorylase?

A

phosphoprotein phosphatase

17
Q

How is glycogen synthase enzyme regulated?

What is the active & inactive forms?

A

via phosphorylation

  • glycogen synthase-a: active & dephosphorylated
  • glycogen synthase-b: inactive and phosphorylated
18
Q

How does glucagon impact cells?

A

increase [cAMP] levels in the liver

19
Q

How does epinephrine impact cellular metabolism?

A
  • increase [cAMP] in liver & muscle cells
    • inhbits glycolysis & stimulates gluconeogenesis in liver
    • stimulates lycolysis in muscle cells
  • increae [Ca2+] in liver
20
Q

How does insulin impact cellular metabolism?

A
  • inhibits glycogenolysis and stimulates glycogenesis in both liver & muscle
  • effects are opposite those of cAMP
21
Q

Glycogen storage diseases are characterized by what features?

A

deposition of abnormal type or quantity of glycoen in tissue

OR

failure to mobilize glycogen

22
Q

Identify the enzyme effected by the provided glycogen storage disorder:

GSD0a

A

liver isozyme of glycogen synthase

glycogen synthase-2 (GYS2)

23
Q

Identify the enzyme affected & mutation associated with the following glycogen storage disease:

Cori / Forbes

A

liver and muscle debranching enzyme

GSD3

24
Q

Identify the enzyme affected & mutation associated with the following glycogen storage disease:

Anderson

A

branching enzyme

GSD4

25
Q

Identify the enzyme affected & mutation associated with the following glycogen storage disease:

McArdle

A

muscle phosphorylase

GSD5

26
Q

Identify the enzyme affected & mutation associated with the following glycogen storage disease:

Hers

A

liver phosphorylase

GSD6

27
Q

Identify the enzyme affected in the following glycogen storage disease:

GSD9a / GSD9b

A

phosphorylase kinase

beta-subunit of PK

S3B2 Biochemistry (9 decks)

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