Lecture 35: RECEPTORS AND CELL SIGNALLING

Question 1

Why do we need fuel stores?

Answer 1

Because the body cannot store ATP

Question 2

What must happen because the body cannot store ATP?

Answer 2

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

Question 3

What are the reasons for storing fuel?

Answer 3

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

Question 4

What is fat stored as?

Answer 4

Triacylclycerols as fat droplets

Question 5

Where is fat stored?

Answer 5

In adipose tissue

Question 6

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

Answer 6

It can be converted to stored fat

Question 7

What is there an unlimited amount of?

Answer 7

Fat stores

Question 8

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

Answer 8

Chylomicrons

Question 9

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

Answer 9

Glucose

Question 10

What are fatty acids activated to?

Answer 10

Fatty acyl-CoA

Question 11

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

Answer 11

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

Question 12

What is synthesis of TAG’s stimulated by?

Answer 12

Insulin

Question 13

What does lipoprotein lipase do?

Answer 13

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

Question 14

What is the pathway for fat to TAG’s?

Answer 14

Fat> chylomicrons> fatty acids > TAG

Question 15

What is the pathway for glucose to TAG?

Answer 15

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

Question 16

What happens in fatty acid activation?

Answer 16

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

Question 17

What molecule begins conversion to glycogen?

Answer 17

dihydroxyacetone phosphate

Question 18

What is dihydroxyacetone phosphate converted to?

Answer 18

Glycerol phosphate by glycerol-3-phosphate dehydrogenase

Question 19

What is glycerol-phosphate converted to?

Answer 19

glycerol to triacylglycerol which requires several steps

Question 20

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

Answer 20

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

Question 21

What happens in mobilisation of TAG’s?

Answer 21

Hydrolysis of TAG’s

Question 22

What is hydrolysis of TAG’s catalysed by?

Answer 22

Hormone-sensitive lipase

Question 23

What is hormone sensitive lipase stimulated by?

Answer 23

Adrenaline and glucagon

Question 24

What is the result of hydrolysis of TAG’s ?

Answer 24

Release of free fatty acids and glycerol

Question 25

What is glycogen?

Answer 25

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

Question 26

Where is glycogen stored?

Answer 26

In the liver and as granules in the cytoplasm

Question 27

Where does glycogen synthesis occur?

Answer 27

Mainly in the liver and muscle immediately after a meal

Question 28

What does glycogen synthesis require?

Answer 28

Energy inputs (ATP and UTP)

Question 29

What is the activated high energy precursor for glycogen synthesis?

Answer 29

UDP-glucose

Question 30

What enzymes are required for glycogen synthesis?

Answer 30

Glycogen synthase and branching enzyme

Question 31

What is glycogen synthesis stimulated by?

Answer 31

Insulin

Question 32

What is the steps of glycogen synthesis?

Answer 32

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)

Question 33

What catalyses the first step of glycogen synthesis?

Answer 33

hexokinase

Question 34

What happens in the first step of glycogen synthesis?

Answer 34

Trapping in cell

Question 35

What catalyses the second step of glycogen synthesis?

Answer 35

Mutase

Question 36

What happens in the second step of glycogen synthesis?

Answer 36

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

Question 37

What is the last step of glycogen synthesis catalysed by?

Answer 37

Glycogen synthase which is stimulated by insulin

Question 38

What is there only so much space for?

Answer 38

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

Question 39

How is glycogen degraded?

Answer 39

By glycogenolysis

Question 40

What happens with liver glycogen?

Answer 40

It is released into the blood for the brain

Question 41

What happens with muscle glycogen?

Answer 41

It releases fuel for glycolysis within muscle cells

Question 42

What can happen with excess glucose carbon?

Answer 42

It can be converted to fatty acids

Question 43

Where does glucose > fatty acids occur?

Answer 43

Mainly in the liver

Question 44

How is the glucose > fatty acids process described?

Answer 44

Complex, energy requiring

Question 45

How are the fatty acids from glucose exported?

Answer 45

As TAG's in VLDL

Question 46

What is glucose > fatty acids stimulated by?

Answer 46

Insulin

Question 47

What is the enzyme which converts glucose to fatty acids?

Answer 47

Fatty acid synthase complex

Question 48

What are the features of fatty acid synthase complex?

Answer 48

7 activities (catalytic sites)

Question 49

What does the fatty acid synthase complex need?

Answer 49

NADPH

Question 50

What does the fatty acid synthase complex make?

Answer 50

Palmitic acid

Question 51

What is the main fuel for the brain?

Answer 51

Glucose (can't use fatty acids)

Question 52

What is the main fuel for RBC's?

Answer 52

Glucose

Question 53

What is the main fuel for the liver?

Answer 53

Mostly fatty acids

Question 54

What is the main fuel for the heart?

Answer 54

mostly fatty acids

Question 55

What is the main fuel for resting muscle?

Answer 55

Mostly fatty acids

Question 56

What is the main fuel for marathon muscle?

Answer 56

Mix of fatty acids and glucose