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Flashcards in Biochemistry Deck (74)
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1

What is glycogenesis?

Synthesis of glycogen from glucose

2

What is glycogenolysis?

Breakdown of glycogen to form glucose

3

Glycogenolysis occurs by hydrolysis. True/False?

False
Occurs by phosphorolysis

4

Where is glycogen stored in the body?

Liver
Muscle cells

5

What is the role of muscle glycogen?

Not used to maintain blood glucose; provides energy via glycolysis and TCA cycle during physical activity

6

Which bonds link glucose molecules to form glycogen?

Alpha-1,4-glycosidic bonds

7

Which bonds create branches in the glycogen chain?

Alpha-1,6-glycosidic bonds

8

Glycogen formation can be started by two glucose monomers joining together. True/False?

False
Glucose residues can only be added to an existing glycogen chain

9

What is required to begin glycogen formation?

Glycogenin

10

What is Glycogenin?

A glycogen primer containing 4 glucose monomers

11

Which enzyme effectively adds glucose monomers to Glycogenin to produce glycogen?

Glycogen synthase

12

When enough glucose is present, glycogen synthesis begins: glucose-6-phosphate is converted to what?

Glucose-1-phosphate

13

What is formed from glucose-1-phosphate in glycogen synthesis?

UDP-glucose

14

What is UDP-glucose?

Essentially an active form of glucose

15

Glycogen synthase adds only one glucose at a time to UDP-glucose to ultimately form glycogen. True/False?

True

16

How often are branches introduced into the glycogen chain?

Every 10 glucose molecules

17

When does glycogenolysis occur?

Between meals to maintain blood glucose levels

18

Which enzyme catalyses glycogenolysis?

Glycogen phosphorylase

19

Glycogen phosphorylase cleaves off only one glucose at a time from glycogen. True/False?

True

20

What are the 2 regulatory actions of insulin upon glycogen synthesis?

Stimulates glycogen synthesis
Inhibits glycogen phosphorylase

21

What are the 2 regulatory actions of glucagon upon glycogenolysis?

Stimulates glycogen breakdown
Inhibits glycogen synthase

22

What is gluconeogenesis? When does it occur?

Synthesis of glucose from non-carbohydrate precursors
Occurs when glycogen stores are completely depleted

23

Where does gluconeogenesis mainly occur?

Liver

24

Name the 3 main precursors for gluconeogenesis

Lactate (lactic acid)
Amino acids
Glycerol

25

Which TCA cycle intermediate is needed for gluconeogenesis? Why is it needed?

Oxaloacetate (4C)
Accepts acetyl groups from fat breakdown

26

Describe the Cori Cycle

Blood transports lactate to liver
Liver converts lactate to glucose
Glucose is released into blood

27

Which type of amino acids can be used to synthesise new glucose?

Glucogenic amino acids

28

Which type of amino acids cannot be used to synthesise new glucose?

Ketogenic amino acids

29

What effect do insulin and glucagon have on gluconeogenesis?

Insulin inhibits gluconeogenesis
Glucagon stimulates gluconeogenesis

30

Does ATP stimulate gluconeogenesis?

Yes