Glycogen Metabolism Flashcards

1
Q

What is the name of the sugar-nucleotide used in glycogen synthesis?

A

UDP - Glucose

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2
Q

What does the formation of UDP-Glucose allow?

Where is the UDP group added?

A
  • It activates the sugar for transfer
  • Added to reducing end of sugar
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3
Q

In a growing glycogen chain, where are new monosaccharides added?

A

To the non-reducing end

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4
Q

A growing chain of glycogen is elongated:

A) 1 sugar at a time

B) 2 sugars at a time

C) By joining linear polysaccharide chains together

A

A

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5
Q

Describe how branching enzyme creates branches in the growing glycogen chain.

A

The enzyme removes a section of the chain and relocates it to an internal sugar and forms an alpha 1–>6 linkage

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6
Q

Why is branching advantageous for the structure of glycogen?

A

When glycogen is degraded, it is done at the non-reducing end. If the molecule is linear, the only 1 glucose molecule will be released at a time. If the molecule is branched, multiple non-reducing ends are available to be released resulting in greater glucose availability.

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7
Q

_____ is the primer used for glycogen synthesis.

A) Glucogenin

B) Glucouridine

C) Glycogenin

D) Glycosamine

A

C

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8
Q

Describe the process of glycogenin initiation of glycogen synthesis.

A

Glycogenin is a protein. It has a specific tyrosine residue that self glucates (reacts with 8 monomers of UDP-glucose) non-enzymatically to form a preliminary glucose chain. Once glucated, glycogen synthase and branching enzyme act on the primed glycogenin to create glycogen.

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9
Q

Describe the structure of mature glycogen

A
  • Glycogenin core
  • 12 tiers of glycogen polymers
  • Each tier has 12-14 glucose and 2 branches
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10
Q

Glycogen phosphorylase is responsible for breaking down glycogen. Describe this process.

A

Enzyme adds inorganic phosphate across the glycosidic bond to generate glucose - 1 - phosphate. This occurs at the terminal glucose monomer in glycogen chains/branches.

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11
Q

How can glucose metabolism regulate glycogen phosphorylase?

A

If glycogen breakdown outpaces glucose utilization, the glucose monomers can feedback and inhibit glycogen phosphorylase to inhibit further production of glucose and breakdown of glycogen.

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12
Q

What is the isoform of glycogen phosphorylase in the muscle cells called?

A

Myophosphorylase

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