Lecture 36: STARVATION

Question 1

What is needed for survival during starvation?

Answer 1

supply the brain with fuels, supply other tissues with fuels and conserve as much protein as possible

Question 2

How much fuel does the brain use?

Answer 2

120g of glucose per day

Question 3

What is the fuel for other tissues?

Answer 3

Mainly fatty acids

Question 4

Why does protein need to be conserved?

Answer 4

To maintain structure and function

Question 5

What is the main hormone involved in survival during starvation?

Answer 5

GLucagon

Question 6

Where is glucagon produced?

Answer 6

By pancreas alpha cells when blood glucose drops

Question 7

How much fat is there?

Answer 7

At leas 15kg

Question 8

How much energy does the fat stores give?

Answer 8

Enough for at least 40 days of starvation

Question 9

What stimulates lipolysis?

Answer 9

Glucagon

Question 10

What can fatty acids be used by?

Answer 10

All aerobic tissues except the brain

Question 11

What are TAG’s broken down into?

Answer 11

glycerol and free fatty acids (complexed to albumin in blood)

Question 12

What breaks down triacylyglycerols?

Answer 12

Hormone sensitive lipase

Question 13

What stimulates hormone sensitive lipase?

Answer 13

Glucagon and adrenaline

Question 14

What does glycerol do?

Answer 14

Enters the blood and goes to the liver

Question 15

What do free fatty acids do?

Answer 15

Go to all aerobic tissues except the brain

Question 16

How much glucose comes from glycerol?

Answer 16

Around 20g

Question 17

How much glucose is in liver glycogen?

Answer 17

About 90-120g (enough for 1 day)

Question 18

What happens to liver glycogen?

Answer 18

It is mobilised back to glucose

Question 19

What is glycogenolysis stimulated by?

Answer 19

Glucagon

Question 20

What enzymes are used in glycogenolysis?

Answer 20

Glycogen phosphorylase and debranching enzyme

Question 21

What is the first step of glycogenolysis?

Answer 21

Glycogen + Pi > glucose-1-phosphate catalysed by phosphorylase

Question 22

What is the second step of glycolysis?

Answer 22

Glucose-1-phosphate <> glucose-6-phosphate catalysed by mutase

Question 23

What is the third step of glycgenolysis?

Answer 23

Glucose-6-phosphate + H2O > glucose + Pi catalysed by glucose-6-phosphatase

Question 24

Where does gluconeogenesis occur?

Answer 24

Mainly in the liver (also kidney cortex)

Question 25

What is gluconeogenesis?

Answer 25

The synthesis of glucose from lactate, alanine and glycerol (3 carbon compounds)

Question 26

where is lactate from?

Answer 26

Muscle glycogen

Question 27

Where is alanine from?

Answer 27

Muscle protein

Question 28

Where is glycerol from?

Answer 28

Adipose tissue (TAG)

Question 29

What is gluconeogenesis stimulated by?

Answer 29

Glucagon

Question 30

What provides the energy (ATP) required fro gluconeogenesis?

Answer 30

Fatty acid oxidaiton

Question 31

What uses most of the glucose from gluconeogenesis?

Answer 31

The brain

Question 32

Can fatty acids (acetyl CoA) be used to make glucose?

Answer 32

No, because they are 2C compounds but can via beta oxidation provide ATP and NADH for gluconeogenesis

Question 33

How much protein is in the body?

Answer 33

10-15kg

Question 34

Is there specific storage proteins?

Answer 34

No

Question 35

What must happen with some protein?

Answer 35

It must be degraded to amino acids to make glucose

Question 36

What can loss of too much protein cause?

Answer 36

Structural and functional damage so proteins must be conserved as much as possible

Question 37

How are ketone bodies synthesised?

Answer 37

In the liver from fatty acids

Question 38

What is the process of forming ketone bodies?

Answer 38

mobilisation of TAG's from adipose tissue > fatty acids > 2acetyl-CoA via beta oxidation > acetoacetate via ketogenesis <> beta hydroxybutyrate

Question 39

What are the ketone bodies?

Answer 39

Acetoacetate and beta hydroxybutyrate

Question 40

What are ketone bodies used by?

Answer 40

The starving brain as an energy source

Question 41

How much energy comes from ketone bodies?

Answer 41

50g/day (still need 50g of alanine)

Question 42

What can fatty acids be used by?

Answer 42

Essentially all aerobic tissues (except brain); essentially unlimited supply from TAG's

Question 43

What are used by the brain?

Answer 43

Ketone bodies

Question 44

What happens as a result of the brain using ketone bodies?

Answer 44

It needs less glucose (only about 50g/day) so muscle degradation can slow down (not so many amino acids needed for gluconeogenesis) and the body can survive for longer