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JL Gastrointestinal > Biochemistry > Flashcards

Flashcards in Biochemistry Deck (313)
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1

What is glycogenolysis?

The breakdown of glycogen to form glucose. It is accomplished by phosphorylis.

2

What is the main storage form of glucose in the liver and muscle cells?

Glycogen

3

When is liver glycogen broken down?

In between meals

4

What is liver glycogen released to maintain?

Blood glucose levels for red blood cells and the brain

5

What type of glycogen can only be consumed within the muscle cells?

Muscle glycogen

6

Where can muscle cells not release glycogen into?

The blood stream

7

What provides energy via glycolysis and the TCA cycle during bursts of physical activity?

Muscle glycogen

8

What does glycogenolysis fluctuate depending upon?

Meal times

9

What is the name of the pathway which generates new glucose from non-carbohydrate precursors?

Gluconeogenesis

10

What is the primary source of glucose overnight when hepatic glycogen is depleted?

Gluconeogenesis

11

What is a polymer consisting of single glucose molecules linked together to form chains?

Glycogen

12

What are glycogen molecules joined by?

An alpha 1-4 glycosidic link.

13

What are the branches of glycogen introduced by?

Alpha 1-6- glycosidic link.

14

How are new molecules added, and old molecules cleaved off from glycogen?

Free glucose joins onot the ends and glucose molecules are cleaved off the ends

15

What can glucose residues only be added to?

An existing glycogen chain.

16

What protein is found in the centre of glycogen?

Glycogenin

17

What substance has a catalytic activity which adds small number of glucose molecules to itself?

Glycogenin

18

What is the enzyme which synthesises glycogen?

Glycogensythase

19

What is a glycogen primer containing at least 4 glucose residues covalantly attached to?

Glycogenin

20

What has to first happen to glucose before it can be used for any further metabolic pathways?

It has to be phosphorylated

21

What is glucose phosphorylated to?

Glucose-6-phosphate

22

What, in the initial pathway of glycogen synthesis, traps the glucose in the cell?

Phosphorylation of glucose to glucose-6-phosphate

23

Once glucose has been trapped in the cell, by phosphorylation of glucose to glucose-6-phosphate - what two choices does the cell have?

If cell needs energy it can breakdown glucose-6-phosphate in glycolysis, however if plenty of glucose is present then glucose-6-phosphate can be used for the synthesis of glycogen.

24

Once it has been decided that glucose-6-phosphate will synthesise glycogen, what is the initial step?

Glucose-6-phosphate has to be converted to glucose-1-phosphate

25

What catalyses glucose-6-phosphate to glucose-1-phosphate?

Phosphoglucomutase

26

In the synthesis of glycogen, once glucose-6-phosphate is converted to glucose-1-phosphate by phosphoglucomutase, what then happens to the glucose-1-phosphate?

It has to be activated to form UDP-glucose

27

What can be considered an actived form of glucose and acts as a substrate for glycogen synthase?

UDP-glucose

28

In the synthesis of glycogen, once UDP-glucose is activated, what does glycogen synthase do to it?

Takes the glucose part of UDP-glucose and covalently bonds it ontop hte ends of existing glycogen.

29

In glycogen synthesis, what happens to the UDP that is left over, once glycogen synthase has taken the glucose part away from it?

It is phosphorylated again to form UTP

30

How much ATP does the phosphorylation of UDP to UTP consume?

1 ATP