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BIOC192 > Lecture 35: RECEPTORS AND CELL SIGNALLING > Flashcards

Lecture 35: RECEPTORS AND CELL SIGNALLING Flashcards

1
Q

Why do we need fuel stores?

A

Because the body cannot store ATP

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2
Q

What must happen because the body cannot store ATP?

A

ATP must be made in the cell at the time it is needed, at the rate it is needed by oxidising fuels

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3
Q

What are the reasons for storing fuel?

A

to maintain a supply of glucose between meals, to provide immediate fuel for increased activity and for long periods of time when food intake may be inadequate

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4
Q

What is fat stored as?

A

Triacylclycerols as fat droplets

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5
Q

Where is fat stored?

A

In adipose tissue

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6
Q

What can be done with excess fat and carbohydrate from the diet?

A

It can be converted to stored fat

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7
Q

What is there an unlimited amount of?

A

Fat stores

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8
Q

Where do the fatty acids for synthesis of TAG’s come from?

A

Chylomicrons

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9
Q

Where does the glycerol backbone fro synthesis of TAG’s come from?

A

Glucose

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10
Q

What are fatty acids activated to?

A

Fatty acyl-CoA

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11
Q

What happens after of activation of fatty acids to acyl-CoA?

A

Esterification of acyl groups to glycerol-3-phosphate (FA’s attached)

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12
Q

What is synthesis of TAG’s stimulated by?

A

Insulin

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13
Q

What does lipoprotein lipase do?

A

Releases fatty acids from VLDL’s (glucose) and chylomicrons (fat) and is stimulated by insulin

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14
Q

What is the pathway for fat to TAG’s?

A

Fat> chylomicrons> fatty acids > TAG

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15
Q

What is the pathway for glucose to TAG?

A

Glucose > glucose > Glucose > acetyl-CoA> FA > TAG > VLDL > VLDL > FA > TAG

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16
Q

What happens in fatty acid activation?

A

Fatty acid (R-COOH) + CoA-SH + ATP > Fatty acyl CoA (R-CO.SCoA) + AMP + PPi catalysed by fatty acylCoA synthetase

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17
Q

What molecule begins conversion to glycogen?

A

dihydroxyacetone phosphate

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18
Q

What is dihydroxyacetone phosphate converted to?

A

Glycerol phosphate by glycerol-3-phosphate dehydrogenase

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19
Q

What is glycerol-phosphate converted to?

A

glycerol to triacylglycerol which requires several steps

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20
Q

What are the enzymes involved in formation of glycerol from glycolysis?

A

Glycerol-3-phosphate acyltransferase and phosphatidate phosphatase followed by diacylglycerol acyltransferase

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21
Q

What happens in mobilisation of TAG’s?

A

Hydrolysis of TAG’s

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22
Q

What is hydrolysis of TAG’s catalysed by?

A

Hormone-sensitive lipase

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23
Q

What is hormone sensitive lipase stimulated by?

A

Adrenaline and glucagon

24
Q

What is the result of hydrolysis of TAG’s ?

A

Release of free fatty acids and glycerol

25
Q

What is glycogen?

A

A branched polysaccharide of alpha-1,4 and alpha-1,6 glycosidic bonds

26
Q

Where is glycogen stored?

A

In the liver and as granules in the cytoplasm

27
Q

Where does glycogen synthesis occur?

A

Mainly in the liver and muscle immediately after a meal

28
Q

What does glycogen synthesis require?

A

Energy inputs (ATP and UTP)

29
Q

What is the activated high energy precursor for glycogen synthesis?

A

UDP-glucose

30
Q

What enzymes are required for glycogen synthesis?

A

Glycogen synthase and branching enzyme

31
Q

What is glycogen synthesis stimulated by?

A

Insulin

32
Q

What is the steps of glycogen synthesis?

A
  1. Glucose + ATP > ADP + glucose-6-phosphate
  2. Glucose-6-phosphate > glucose-1-phosphate
  3. Glucose-1-phosphate + UTP > UPD-glucose + PPi
  4. UPD-glucose + glycogen(n) > UPD + glycogen (n+1)
33
Q

What catalyses the first step of glycogen synthesis?

A

hexokinase

34
Q

What happens in the first step of glycogen synthesis?

A

Trapping in cell

35
Q

What catalyses the second step of glycogen synthesis?

A

Mutase

36
Q

What happens in the second step of glycogen synthesis?

A

A phosphate is transferred to commit to glycogen synthesis and diverge from glycolysis

37
Q

What is the last step of glycogen synthesis catalysed by?

A

Glycogen synthase which is stimulated by insulin

38
Q

What is there only so much space for?

A

Glycogen; excess glucose is converted to acetyl-CoA and then to fatty acids by the fatty acid synthase complex in liver cytosol

39
Q

How is glycogen degraded?

A

By glycogenolysis

40
Q

What happens with liver glycogen?

A

It is released into the blood for the brain

41
Q

What happens with muscle glycogen?

A

It releases fuel for glycolysis within muscle cells

42
Q

What can happen with excess glucose carbon?

A

It can be converted to fatty acids

43
Q

Where does glucose > fatty acids occur?

A

Mainly in the liver

44
Q

How is the glucose > fatty acids process described?

A

Complex, energy requiring

45
Q

How are the fatty acids from glucose exported?

A

As TAG’s in VLDL

46
Q

What is glucose > fatty acids stimulated by?

A

Insulin

47
Q

What is the enzyme which converts glucose to fatty acids?

A

Fatty acid synthase complex

48
Q

What are the features of fatty acid synthase complex?

A

7 activities (catalytic sites)

49
Q

What does the fatty acid synthase complex need?

A

NADPH

50
Q

What does the fatty acid synthase complex make?

A

Palmitic acid

51
Q

What is the main fuel for the brain?

A

Glucose (can’t use fatty acids)

52
Q

What is the main fuel for RBC’s?

A

Glucose

53
Q

What is the main fuel for the liver?

A

Mostly fatty acids

54
Q

What is the main fuel for the heart?

A

mostly fatty acids

55
Q

What is the main fuel for resting muscle?

A

Mostly fatty acids

56
Q

What is the main fuel for marathon muscle?

A

Mix of fatty acids and glucose

BIOC192 (38 decks)

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