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Flashcards in Glucose Deck (62):
1

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

30.5kJ/mol (relatively low energy intermediate)

2

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

220kJ/mol (relatively high energy intermediate)

3

Anaerobic metabolism of glucose provides how many ATP?

2

4

Aerobic metabolism of glucose provides how many ATP?

32

5

What is glycogen?

Fasting reserve of glucose

6

Glucose and galactose are what kind of sugar?

Aldose

7

Fructose is what kind of sugar?

Ketose

8

How does glucose enter cells?

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

9

Red blood cells are obligated to which form of metabolism?

Anaerobic (they have no mitochondria)

10

Anaerobic glycolysis produces

lactate

11

Gluconeogenesis

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

12

Which sugar is correlated with obesity?

High fructose in processed foods

13

What is the cellular substrate for ATPases?

Mg-ATP (more stable)

14

Most of the electrons generated in metabolism are stored in

NADH

15

The general formula for carbohydrates is

Cn(H2O)n

16

Monosaccharides have how many carbons?

3-7

17

Glucose has how many carbons?

6

18

Fructose has how many carbons?

6

19

D sugars in Fischer projections have

-OH of highest chiral carbon on right

20

How is the Fischer projection of glucose remembered?

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

21

Why do fats have more energy than carbohydrates?

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

22

Maltose

2 glucose

23

Where do circulation problems in diabetes arise from?

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

24

Fasting blood glucose

4-5mM

25

What is the renal threshold for glucose?

10mM - beyond this it comes out in urine

26

What is the cause of retinopathy in diabetes?

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

27

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

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

28

GLUT1 are located

ubiquitous

29

GLUT2 are located

liver, pancreatic islets, intestine

30

GLUT4 are located

muscle, fat, heart

31

What is the function of GLUT1 transporters?

Basal glucose uptake

32

What is the function of GLUT2 transporters?

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

33

What is the function of GLUT4 transporters?

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

What happens to GLUT4 in diabetes?

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

Glucose-6-phosphatase is active only in

liver (mostly) and kidney

36

What is the role of glucose-6-phosphatase?

release of free glucose made from glycogen

37

What determines glucose uptake by GLUT transporters?

insulin:glucagon

38

In starvation mode, the liver

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

39

In the fed state where insulin goes up, the liver

takes up glucose and stores it as glycogen

40

What is the equation for glucose metabolism?

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

41

What are the products of glycolysis?

2pyruvate, 2NADH, 2ATP, 2H20

42

How much energy from glucose is captured as ATP?

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

43

What is the committed step of glycolysis?

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

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

phosphocreatine in muscle; produces ATP

45

Endurance activity depends on

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

46

Lactate is converted to glucose in

the liver (Cori cycle)

47

What is the Cori cycle?

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

48

What cells depend on anaerobic glycolysis?

retinal cells, red blood cells

49

Why are there no mitochondria in the retina?

mitochondrial cytochromes absorb light

50

The brain requires how many grams of glucose per day?

120g

51

What are the carbon sources for gluconeogenesis?

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

52

Glycerol undergoes gluconeogenesis in the

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

53

Lactose is made of

glucose and galactose (disaccharide)

54

Utilization of lactose requires

epimerisation of galactose (4-epimer) back to glucose

55

Galactosaemia is the failure of which enzymes?

galactokinase, galactose-1-phosphate uridylytransferase, epimerase

56

Sucrose is made of

glucose and fructose

57

What are the metabolic products of fructose?

dihydroxyacetone phosphate (DHAP) and glyceraldehyde (GAP)

58

What is the action of fructose on insulin?

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

59

What is the action of fructose on leptin?

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

60

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

turning down apetite to control body weight

61

What is the action of fructose on ghrelin?

Does not suppress it ie hunger and appetite stay increased

62

Fructose increases which type of cholesterol?

LDL