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Flashcards in Metabolism - Energy Storage Deck (12):
0

What are the steps of glycogen synthesis and the enzymes used?

Glucose + ATP ---> ADP + G6P
Hexo/glucokinase

G6P ---> G1P
Phosphoglucomutase

G1P + UTP + H2O ---> UDPGlucose + Pi

UDPGlucose + glycogen ---> more glycogen + UDP
Glycogen synthase/branching enzyme

1

How is glycogen synthesis and breakdown regulated?

Insulin dephosphorylates and therefore stimulates glycogen synthase, and inhibits glycogen phosphorylase

Glucagon and adrenaline phosphorylate and therefore inhibits glycogen synthase, and stimulates glycogen phosphorylase.

2

When does glycogen degradation occur in the skeletal muscle and liver?

Liver during fasting or stress

Skeletal muscle during intense exercise

3

What are the steps of glycogen degradation?

Glycogen + Pi ---> G1P + less glycogen
Glycogen phosphorylase/debranching enzyme

G1P ---> G6P
Phosphoglucomutase

IN MUSCLE
G6P enters glycolysis

IN LIVER
G6P + H2O ---> Glucose + Pi
Glucose-6-phosphatase
(Glucose enters bloodstream)

4

What is Von Gierkes disease?

A deficiency in glucose-6-phosphatase
= excess glycogen stored in liver = liver damage

5

How may disorders diminishing glycogen stores result?

Hypoglycaemia

6

Around what hour after eating does gluconeogenesis begin?

After 8h

7

What enzymes are required for gluconeogenesis?

PEPCK
Fructose-1,6-bisphosphatase

8

What can be fed into gluconeogenesis?

Galactose
Fructose
Glycerol (derived from fat metabolism)
Lactate
Gluconeogeneic amino acids

9

Why can fatty acids not be converted directly into glucose?

Because they form acetyl CoA first, and step 10 in glycolysis is irreversible = can't work back.

10

Where does gluconeogenesis occur and what is its purpose?

In liver and kidney cortex in extreme conditions (as it is highly metabolically active so is desperate for glucose)

It produces new glucose from non carbohydrate precursors.

11

How is gluconeogenesis regulated?

Insulin dephosphorylates and inhibits PEPCK and fructose-1,6-bisphosphate.

Glucagon/adrenaline phosphorylate and stimulate PEPCK and fructose-1,6-bisphosphate.