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Year 1 Summative 1 > BMS07-1026 Glucose & Glycogen Metabolism > Flashcards

BMS07-1026 Glucose & Glycogen Metabolism Flashcards

1
Q

Draw the structure of glucose

A

https://www.bing.com/images/search?view=detailV2&id=73B0212C46A6461A6248F9312A062378306EC52A&thid=OIP.nDAaAj8WAe2ZBLNasQtLQAHaFB&mediaurl=http%3A%2F%2Fbakerpedia.com%2Fwp-content%2Fuploads%2F2013%2F02%2Fglucose.jpg&exph=1687&expw=2486&q=glucose&selectedindex=1&ajaxhist=0&vt=0&eim=1,6

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2
Q

Draw the structure of glycogen

A

https://www.bing.com/images/search?view=detailV2&id=73844F136417289B23F4E1B7C5757D29F066A791&thid=OIP.npcE8pucrEssKRNQZiwB2wHaCn&mediaurl=http%3A%2F%2Fwww.celebritydiagnosis.com%2Fwp-content%2Fuploads%2F2010%2F01%2FGlycogen.jpg&exph=530&expw=1503&q=glycogen&selectedindex=0&ajaxhist=0&vt=0&eim=1,6

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3
Q

What is the difference between glucose and glycogen?

A

Glycogen is a polysaccharide of glucose

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4
Q

What is gluconeogenesis?

A

Glucose from AA or FA

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5
Q

How is glycogen used in the liver?

A

It’s converted to glucose-6-phosphate and then looses a Pi to form glucose

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6
Q

How is glucose-6-phosphate converted to glucose?

A

hydrolyses glucose-6-phopshate so a Pi is released, forming glucose

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7
Q

Why do the final products of glycogenolysis differ in the liver and muscle?

A

In the muscle the end product is glucose-6-phosphate not just glucose as it has to enter the glycolysis pathway

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8
Q

What is glycogenolysis?

A

Glucose from glycogen

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9
Q

Describe glycogen breakdown in the liver and kidney

A

Glycogen is converted to glucose-1-phosphate using the enzyme glycogen phosphorylase (stimulated by insulin) and a debranching enzyme, by adding a Pi

Glucose-1-phosphate is converted to glucose-6-phosphate using the enzyme phosphoglucomutase

Glucose-6-phosphate is then converted to glucose using the enzyme glucose-6-phosphatase and adding a water

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10
Q

Describe the osmolarity of glucose and glycogen

A

Glucose is osmotically active while glycogen has a low osmolarity

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11
Q

What stimulates glycogenolysis in the muscle and liver?

A

in the liver insulin and glucagon stimulate it while in the muscle AMP, ATP, Ca and adrenaline stimulate it

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12
Q

Describe the activation of glucose

A

Glucose is converted to glucose-6-phosphate by converting ATP to ADP

Glucose-6-phosphate is converted to glucose-1-phosphate by the enzyme phosphoglucomutase

Glucose-1-phosphate is converted to UDP glucose through the conversion of UTP to PPi and the use of the UDP glucose pyrophosphorylase enzyme

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13
Q

How does glucose activation differ in the liver and muscle?

A

In the muscle hexokinase is the protein kinase at work while in the muscle it’s glucokinase

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14
Q

What is UDP glucose?

A

This is the active form of glucose

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15
Q

Why do we activate glucose?

A

This allows us to reform glycogen

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16
Q

How is glycogen reformed?

A

UDP glucose and a glycogen primer join using the enzyme glycogen synthase (which is activated by insulin) to and a branching enzyme to form glycogen

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17
Q

What are the 4 stages of the glycolysis pathway?

A

Activation- using ATP
Splitting the 6C sugar in half
Oxidation (removing 2H)
ATP synthesis

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18
Q

Which reactions are involved in the activation stage?

A

Reactions 1, 2 and 3

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19
Q

Describe reaction 1

A

D glucose is converted to glucose-6-phosphate
ATP is converted to ADP
Hexokinase or glucokinase catalyses this

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20
Q

Describe reaction 2

A

Glucose-6-phosphate is converted to fructose-6-phosphate

It is catalysed by phosphohexose isomerase

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21
Q

Describe reaction 3

A

Fructose-6-phosphate is converted to fructose-1,6-bisphophate using the enzyme phosphofructokinase
ATP is converted to ADP

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22
Q

Describe reaction 6

A

Glyceraldehyde-3-phosphate is converted to 1,3-bisphosphoglycerate
The enzyme glyceraldehyde-3-phosphate dehydrogenase is used
NAD + Pi is converted to NADH + H

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23
Q

Which step is the oxidation step?

A

Reaction 6

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24
Q

Which step is the activation step?

A

Reaction 1, 2 and 3

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25
Q

Which step is the splitting step?

A

Reaction 4 and 5

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26
Q

Describe reaction 4

A

Fructose-1,6-bisphosphate is converted to glyceraldehyde-3-phosphate and dihydroxyacetone phosphate

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27
Q

Which product from reaction 4 is taken forwards in the reaction chain?

A

Glyceraldehyde-3-phosphate

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28
Q

Describe reaction 5

A

The conversion of dihydroxyacetone phosphate to glyceraldehyde-3-phosphate using the triose phosphate isomerase enzyme

29
Q

What is significant about reaction 6?

A

It swaps a H on glyceraldehyde-3-phosphate to OP which is a high energy bond

30
Q

Which reactions are in the ATP synthesis stage?

A

Reaction 7, 8, 9 and 10

31
Q

What kind of reaction is reaction 7?

A

Substrate level phosphorylation

32
Q

Describe reaction 7

A

1,3-bisphosphoglycerate to 3-phosphohlycerate
This is catalysed by phophoglycerate kinase
ADP is converted to ATP

33
Q

What kind of reaction is reaction 8?

A

Isomerisation

34
Q

Describe reaction 8

A

3-phosphoglycerate is converted to 2-phosphoglycerate using the enzyme phosphoglycerate mutase

35
Q

What changes during reaction 8?

A

The OP group swaps places with the OH group from the reactant to the product

36
Q

Describe reaction 9

A

2-phosphoglycerate is converted to phosphoenol pyruvate
Enolase catalyses this
Water is released

37
Q

What is significant about reaction 9?

A

A high energy phosphate bond is formed

38
Q

What kind of reaction is reaction 10?

A

Substrate level phosphorylation

39
Q

Describe reaction 10

A

Phosphoenolpyruvate is converted to pyruvate
Pyruvate kinase catalyses this
ADP is converted to ATP

40
Q

What is the ATP yield from glycolysis?

A

The early stages use 2 ATP but the later ones make 4 ATP so there is a net yield of 2 ATP

41
Q

What happens during anaerobic glycolysis?

A

Instead of pyruvate being metabolised to carbon dioxide it’s converted to lactate to regenerate NAD from NADH + H

42
Q

Describe the conversion of pyruvate to lactate in the liver and muscle

A

In the muscle lactate dehydrogenase catalyses the conversion forming NAD from NADH + H
In the liver the reverse of this reaction occurs

43
Q

How do microorganisms use pyruvate?

A

To form ethanol in fermentation regenerating NAD for glycolysis

44
Q

Other than forming lactate and ethanol, what is another metabolic fate of pyruvate? (4)

A

Form acetyl coenzyme A which is converted to fatty acids when there is an excessive calorie intake

Form acetyl coenzyme A which is used in the citric acid cycle to form carbon dioxide

Form alanine by transamination

To oxaloacetate and then glucose 6 phosphate which can be converted back to pyruvate

45
Q

How is glycolysis used in the body?

A

In skeletal muscle during intense exercise
In RBC
In the brain

46
Q

Where does glycolysis occur

A

In the cytosol

47
Q

Why isn’t the synthesis and breakdown of glycogen direct reversals of eachother?

A

So independent regulation can occur and there isn’t a futile cycle

48
Q

What is special about glycolysis?

A

It can occur in aerobic and anaerobic conditions

49
Q

How is glycolysis linked to the citric acid cycle?

A

Pyruvate can enter it

50
Q

How is glycogen adapted for glycolysis?

A

Has many branches so it breaks down quickly

51
Q

What is special about muscle cells?

A

They can use glucose-6-phosphate directly it doesn’t need to be converted to glucose

52
Q

Why is UTP energetically favourable?

A

UTP breaks down leaving PPI, PPI instantly breaks down into 2 Pi so the reaction is pulled forwards

53
Q

What is present in most tissues glucokinase or hexokinase?

A

Hexokinase

54
Q

What’s the difference between bis and bi in chemical names?

A

Bi means they are attached while bis means they aren’t

55
Q

Discuss the speed of reaction 5?

A

It happens quickly as glyceraldehyde-3-phosphate is removed very quickly pushing the reaction forwards

56
Q

What is substrate level phosphorylation?

A

Adding a Pi to ADP to form ATP

57
Q

What are the 2 fates of lactate?

A

Converted straight to glucose or put back into the blood stream

58
Q

What is allosteric inhibition?

A

Covalent alteration

59
Q

Which reactions are irreversible?

A

Reaction 1, 10 and 3

60
Q

How is reaction 3 regulated?

A

Phosphofructokinase needs ATP to bind at one site, but when it binds at the other the reaction is slowed.

Insulin activates phosphatase to remove to Pi making it inactive

61
Q

How is reaction 1 regulated? (5)

A

Glucagon activates the GPCR, the alpha units runs off as GDP turns to GTP, this activates adenylyl cyclase, this increases cAMP, this activates protein kinase A, this adds a Pi to glycogen phosphorylase, activating it

Insulin activates phosphodiesterase, converting cAMP to AMP and activates protein phosphatase which dephosphorlyses glycogen phosphorylase

Hexokinase is inhibited by it’s product

Glucagon stops the synthesis of glucokinase

Insulin causes the synthesis of glucokinase

62
Q

How is reaction 10 regulated?

A

A Pi is added to glycogen synthase turning it off

63
Q

How does glycogen regulate glycolysis?

A

It binds to the GPCR causing a conformational change so the alpha subunit is released and converts ATP to cAMP and Pi, cAMP activates hexo/glucokinase which phosphorylyses glycogen phosphorylase to turn the enzyme on

64
Q

What’s the difference between hexokinase and glucokinase?

A

Glucokinase has a higher km so can catalyse the reaction at a faster rate

65
Q

How can pyruvate be formed?

A

From many amino acids

66
Q

How is the irreversible reaction of glycolysis bypassed?

A

Oxloacetate is converted to phosphoenolpyruvate

67
Q

How is the synthesis of oxaloacetate enhanced?

A

Acetyl coenzyme A activates pyruvate carboxylase so more is made

68
Q

What chemicals regulate glycogen phosphorylase?

A

ATP and glucose-6-phosphate

69
Q

How is pyruvate kinase regulated? (3)

A

Fructose 1,6-bisphosphate and ATP activates it

Glucagon phosphorylates it making it inactive by a cAMP dependant protein kinase

Insulin activates phosphatase removes a Pi activating it

Year 1 Summative 1 (56 decks)

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