Glucose

Question 1

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

Answer 1

30.5kJ/mol (relatively low energy intermediate)

Question 2

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

Answer 2

220kJ/mol (relatively high energy intermediate)

Question 3

Anaerobic metabolism of glucose provides how many ATP?

Answer 3

2

Question 4

Aerobic metabolism of glucose provides how many ATP?

Answer 4

32

Question 5

What is glycogen?

Answer 5

Fasting reserve of glucose

Question 6

Glucose and galactose are what kind of sugar?

Answer 6

Aldose

Question 7

Fructose is what kind of sugar?

Answer 7

Ketose

Question 8

How does glucose enter cells?

Answer 8

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

Question 9

Red blood cells are obligated to which form of metabolism?

Answer 9

Anaerobic (they have no mitochondria)

Question 10

Anaerobic glycolysis produces

Answer 10

lactate

Question 11

Gluconeogenesis

Answer 11

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

Question 12

Which sugar is correlated with obesity?

Answer 12

High fructose in processed foods

Question 13

What is the cellular substrate for ATPases?

Answer 13

Mg-ATP (more stable)

Question 14

Most of the electrons generated in metabolism are stored in

Answer 14

NADH

Question 15

The general formula for carbohydrates is

Answer 15

Cn(H2O)n

Question 16

Monosaccharides have how many carbons?

Answer 16

3-7

Question 17

Glucose has how many carbons?

Answer 17

6

Question 18

Fructose has how many carbons?

Answer 18

6

Question 19

D sugars in Fischer projections have

Answer 19

-OH of highest chiral carbon on right

Question 20

How is the Fischer projection of glucose remembered?

Answer 20

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

Question 21

Why do fats have more energy than carbohydrates?

Answer 21

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

Question 22

Maltose

Answer 22

2 glucose

Question 23

Where do circulation problems in diabetes arise from?

Answer 23

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

Question 24

Fasting blood glucose

Answer 24

4-5mM

Question 25

What is the renal threshold for glucose?

Answer 25

10mM - beyond this it comes out in urine

Question 26

What is the cause of retinopathy in diabetes?

Answer 26

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

Question 27

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

Answer 27

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

Question 28

GLUT1 are located

Answer 28

ubiquitous

Question 29

GLUT2 are located

Answer 29

liver, pancreatic islets, intestine

Question 30

GLUT4 are located

Answer 30

muscle, fat, heart

Question 31

What is the function of GLUT1 transporters?

Answer 31

Basal glucose uptake

Question 32

What is the function of GLUT2 transporters?

Answer 32

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

Question 33

What is the function of GLUT4 transporters?

Answer 33

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

Question 34

What happens to GLUT4 in diabetes?

Answer 34

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

Question 35

Glucose-6-phosphatase is active only in

Answer 35

liver (mostly) and kidney

Question 36

What is the role of glucose-6-phosphatase?

Answer 36

release of free glucose made from glycogen

Question 37

What determines glucose uptake by GLUT transporters?

Answer 37

insulin:glucagon

Question 38

In starvation mode, the liver

Answer 38

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

Question 39

In the fed state where insulin goes up, the liver

Answer 39

takes up glucose and stores it as glycogen

Question 40

What is the equation for glucose metabolism?

Answer 40

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

Question 41

What are the products of glycolysis?

Answer 41

2pyruvate, 2NADH, 2ATP, 2H20

Question 42

How much energy from glucose is captured as ATP?

Answer 42

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

Question 43

What is the committed step of glycolysis?

Answer 43

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

Question 44

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

Answer 44

phosphocreatine in muscle; produces ATP

Question 45

Endurance activity depends on

Answer 45

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

Question 46

Lactate is converted to glucose in

Answer 46

the liver (Cori cycle)

Question 47

What is the Cori cycle?

Answer 47

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

Question 48

What cells depend on anaerobic glycolysis?

Answer 48

retinal cells, red blood cells

Question 49

Why are there no mitochondria in the retina?

Answer 49

mitochondrial cytochromes absorb light

Question 50

The brain requires how many grams of glucose per day?

Answer 50

120g

Question 51

What are the carbon sources for gluconeogenesis?

Answer 51

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

Question 52

Glycerol undergoes gluconeogenesis in the

Answer 52

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

Question 53

Lactose is made of

Answer 53

glucose and galactose (disaccharide)

Question 54

Utilization of lactose requires

Answer 54

epimerisation of galactose (4-epimer) back to glucose

Question 55

Galactosaemia is the failure of which enzymes?

Answer 55

galactokinase, galactose-1-phosphate uridylytransferase, epimerase

Question 56

Sucrose is made of

Answer 56

glucose and fructose

Question 57

What are the metabolic products of fructose?

Answer 57

dihydroxyacetone phosphate (DHAP) and glyceraldehyde (GAP)

Question 58

What is the action of fructose on insulin?

Answer 58

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

Question 59

What is the action of fructose on leptin?

Answer 59

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

Question 60

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

Answer 60

turning down apetite to control body weight

Question 61

What is the action of fructose on ghrelin?

Answer 61

Does not suppress it ie hunger and appetite stay increased

Question 62

Fructose increases which type of cholesterol?

Answer 62

LDL