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bioc192 > Lecture 36: STARVATION > Flashcards

Lecture 36: STARVATION Flashcards

1
Q

What is needed for survival during starvation?

A

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

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2
Q

How much fuel does the brain use?

A

120g of glucose per day

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3
Q

What is the fuel for other tissues?

A

Mainly fatty acids

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4
Q

Why does protein need to be conserved?

A

To maintain structure and function

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5
Q

What is the main hormone involved in survival during starvation?

A

GLucagon

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6
Q

Where is glucagon produced?

A

By pancreas alpha cells when blood glucose drops

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7
Q

How much fat is there?

A

At leas 15kg

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8
Q

How much energy does the fat stores give?

A

Enough for at least 40 days of starvation

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9
Q

What stimulates lipolysis?

A

Glucagon

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10
Q

What can fatty acids be used by?

A

All aerobic tissues except the brain

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11
Q

What are TAG’s broken down into?

A

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

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12
Q

What breaks down triacylyglycerols?

A

Hormone sensitive lipase

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13
Q

What stimulates hormone sensitive lipase?

A

Glucagon and adrenaline

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14
Q

What does glycerol do?

A

Enters the blood and goes to the liver

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15
Q

What do free fatty acids do?

A

Go to all aerobic tissues except the brain

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16
Q

How much glucose comes from glycerol?

A

Around 20g

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17
Q

How much glucose is in liver glycogen?

A

About 90-120g (enough for 1 day)

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18
Q

What happens to liver glycogen?

A

It is mobilised back to glucose

19
Q

What is glycogenolysis stimulated by?

A

Glucagon

20
Q

What enzymes are used in glycogenolysis?

A

Glycogen phosphorylase and debranching enzyme

21
Q

What is the first step of glycogenolysis?

A

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

22
Q

What is the second step of glycolysis?

A

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

23
Q

What is the third step of glycgenolysis?

A

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

24
Q

Where does gluconeogenesis occur?

A

Mainly in the liver (also kidney cortex)

25
Q

What is gluconeogenesis?

A

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

26
Q

where is lactate from?

A

Muscle glycogen

27
Q

Where is alanine from?

A

Muscle protein

28
Q

Where is glycerol from?

A

Adipose tissue (TAG)

29
Q

What is gluconeogenesis stimulated by?

A

Glucagon

30
Q

What provides the energy (ATP) required fro gluconeogenesis?

A

Fatty acid oxidaiton

31
Q

What uses most of the glucose from gluconeogenesis?

A

The brain

32
Q

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

A

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

33
Q

How much protein is in the body?

A

10-15kg

34
Q

Is there specific storage proteins?

A

No

35
Q

What must happen with some protein?

A

It must be degraded to amino acids to make glucose

36
Q

What can loss of too much protein cause?

A

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

37
Q

How are ketone bodies synthesised?

A

In the liver from fatty acids

38
Q

What is the process of forming ketone bodies?

A

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

39
Q

What are the ketone bodies?

A

Acetoacetate and beta hydroxybutyrate

40
Q

What are ketone bodies used by?

A

The starving brain as an energy source

41
Q

How much energy comes from ketone bodies?

A

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

42
Q

What can fatty acids be used by?

A

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

43
Q

What are used by the brain?

A

Ketone bodies

44
Q

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

A

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

bioc192 (38 decks)

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