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Metabolism > Glucose > Flashcards

Glucose Flashcards

1
Q

What is the energy of ATP (hydrolysed to ADP)?

A

30.5kJ/mol (relatively low energy intermediate)

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2
Q

What is the energy of NADH (oxidized to NAD+)?

A

220kJ/mol (relatively high energy intermediate)

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3
Q

Anaerobic metabolism of glucose provides how many ATP?

A

2

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4
Q

Aerobic metabolism of glucose provides how many ATP?

A

32

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5
Q

What is glycogen?

A

Fasting reserve of glucose

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6
Q

Glucose and galactose are what kind of sugar?

A

Aldose

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7
Q

Fructose is what kind of sugar?

A

Ketose

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8
Q

How does glucose enter cells?

A

GLUT transporters: 1 (universal), 2 (liver and pancreas), 4 (muscle and adipose; insulin responsive)

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9
Q

Red blood cells are obligated to which form of metabolism?

A

Anaerobic (they have no mitochondria)

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10
Q

Anaerobic glycolysis produces

A

lactate

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11
Q

Gluconeogenesis

A

generates new glucose from glycerol or amino acids, NEVER FROM FAT

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12
Q

Which sugar is correlated with obesity?

A

High fructose in processed foods

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13
Q

What is the cellular substrate for ATPases?

A

Mg-ATP (more stable)

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14
Q

Most of the electrons generated in metabolism are stored in

A

NADH

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15
Q

The general formula for carbohydrates is

A

Cn(H2O)n

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16
Q

Monosaccharides have how many carbons?

A

3-7

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17
Q

Glucose has how many carbons?

A

6

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18
Q

Fructose has how many carbons?

A

6

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19
Q

D sugars in Fischer projections have

A

-OH of highest chiral carbon on right

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20
Q

How is the Fischer projection of glucose remembered?

A

All D except for 3 - all -OH groups are on the right except at carbon 3 (carbon 1 = aldehyde)

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21
Q

Why do fats have more energy than carbohydrates?

A

Carbohydrates contain O and tf are partially hydrated/oxidized reducing the amount of energy we get from burning them

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22
Q

Maltose

A

2 glucose

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23
Q

Where do circulation problems in diabetes arise from?

A

Glycation of blood vessels - amino groups in protein are susceptible to glycation by glucose, generating fructosamine. this makes vessels brittle and prone to clots, leading to blindness and gangrene requiring amputation

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24
Q

Fasting blood glucose

A

4-5mM

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25
Q

What is the renal threshold for glucose?

A

10mM - beyond this it comes out in urine

26
Q

What is the cause of retinopathy in diabetes?

A

When blood glucose is elevated it damages the retinal capillary beds, causing aneurysms and haemorrhage that can cause blindness

27
Q

What is the diagnostic indicator of glycation/uncontrolled high glucose levels in blood?

A

Hb-A1C = glycosylated red Hb; normally 3-5% of Hb but ~15%+ in diabetes

28
Q

GLUT1 are located

A

ubiquitous

29
Q

GLUT2 are located

A

liver, pancreatic islets, intestine

30
Q

GLUT4 are located

A

muscle, fat, heart

31
Q

What is the function of GLUT1 transporters?

A

Basal glucose uptake

32
Q

What is the function of GLUT2 transporters?

A

liver and pancreas response to glucose: formation of glycogen and release of insulin, respectively

33
Q

What is the function of GLUT4 transporters?

A

insulin signal tells GLUT4 (inactive precursor) to migrate to the cell membrane and let in glucose; if you become resistant to insulin or insulin depletes, GLUT4 stays within the cell starving it of glucose while glucose causes damage because it can’t get into cells

34
Q

What happens to GLUT4 in diabetes?

A

low insulin or insulin resistance means there is no insulin signal to muscle, fat, heart cells that triggers movement of GLUT4 to the membrane to let glucose in - the cells are starved of glucose; glucose causes damage because it can’t get into cells

35
Q

Glucose-6-phosphatase is active only in

A

liver (mostly) and kidney

36
Q

What is the role of glucose-6-phosphatase?

A

release of free glucose made from glycogen

37
Q

What determines glucose uptake by GLUT transporters?

A

insulin:glucagon

38
Q

In starvation mode, the liver

A

takes stored glycogen and metabolises it to glucose, released by G6Pase

39
Q

In the fed state where insulin goes up, the liver

A

takes up glucose and stores it as glycogen

40
Q

What is the equation for glucose metabolism?

A

glucose + 2NAD+ +2ADP + 2Pi –> 2pyruvate + 2NADH + 2ATP + 2H20

41
Q

What are the products of glycolysis?

A

2pyruvate, 2NADH, 2ATP, 2H20

42
Q

How much energy from glucose is captured as ATP?

A

2.1% = 61kJ out of a total of 2.8MJ per mole of glucose

43
Q

What is the committed step of glycolysis?

A

fructose-6-phosphate to fructose-1,6-biphosphate by PFK; PFK is only active when cells have low [ATP] because this step is energetically irreversible

44
Q

What energy store is used for short-term bursts of activity (eg first ~5s of 100m dash)

A

phosphocreatine in muscle; produces ATP

45
Q

Endurance activity depends on

A

fatty acids, ketone bodies, blood glucose (aerobic metabolism)

46
Q

Lactate is converted to glucose in

A

the liver (Cori cycle)

47
Q

What is the Cori cycle?

A

carbon cycling between glycogen in muscle and lactate, converted back to glucose in the liver

48
Q

What cells depend on anaerobic glycolysis?

A

retinal cells, red blood cells

49
Q

Why are there no mitochondria in the retina?

A

mitochondrial cytochromes absorb light

50
Q

The brain requires how many grams of glucose per day?

A

120g

51
Q

What are the carbon sources for gluconeogenesis?

A

lactate (post-exercise or anaerobic tissue eg RBCs), amino acids from protein breakdown, glycerol from mobilisation of triacylglycerides in adipose tissue (starvation)

52
Q

Glycerol undergoes gluconeogenesis in the

A

liver; adipose tissue lacks glycerol kinase tf glycerol circulates to the liver

53
Q

Lactose is made of

A

glucose and galactose (disaccharide)

54
Q

Utilization of lactose requires

A

epimerisation of galactose (4-epimer) back to glucose

55
Q

Galactosaemia is the failure of which enzymes?

A

galactokinase, galactose-1-phosphate uridylytransferase, epimerase

56
Q

Sucrose is made of

A

glucose and fructose

57
Q

What are the metabolic products of fructose?

A

dihydroxyacetone phosphate (DHAP) and glyceraldehyde (GAP)

58
Q

What is the action of fructose on insulin?

A

none - it is an isomer of glucose that does not stimulate insulin release from the pancreas

59
Q

What is the action of fructose on leptin?

A

none - it does not increase the production of leptin from fat cells

60
Q

What are the general roles of insulin and leptin suppressed by fructose?

A

turning down apetite to control body weight

61
Q

What is the action of fructose on ghrelin?

A

Does not suppress it ie hunger and appetite stay increased

62
Q

Fructose increases which type of cholesterol?

A

LDL

Metabolism (16 decks)

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