metabolic pathways and ATP production

Question 1

name 4 blood-borne hormones that act as metabolic regulators for glucose

Answer 1

insulin, glucagon, adrenaline, corticosteroids

Question 2

effect of insulin

Answer 2

secreted if glucose levels rise, stimulating uptake and use of glucose (and storage in glycogen/fat)

Question 3

effect of glucagon

Answer 3

secreted if glucose levels fall, stimulating gluconeogenesis and glycogenolysis

Question 4

effect of adrenaline

Answer 4

strong and fast metabolic effects to mobilise glucose (fight or flight)

Question 5

effect of corticosteroids

Answer 5

steroid hormones that increase synthesis of metabolic enzymes

Question 6

what is diabetes mellitus a disorder of

Answer 6

insulin release and signalling

Question 7

describe type 1 diabetes

Answer 7

failure to secrete enough insulin due to B-cell dysfunction

Question 8

describe type 2 diabetes

Answer 8

failure to respond appropriately to insulin levels

Question 9

4 complications of diabetes mellitus

Answer 9

hyperglycaemia (progressive tissue damage), increase in plasma fatty acids and lipoprotein levels (cardiovascular complications), increase in ketone bodies (acidosis), hypoglycaemia (if imperfectly controlled leading to coma)

Question 10

function of hexokinase

Answer 10

converts glucose into glucose-6-phosphate in glycolysis

Question 11

isoforms of hexokinase

Answer 11

different in liver and muscle

Question 12

function of glucose-6-phosphatase

Answer 12

converts glucose-6-phosphate into glucose in gluconeogenesis

Question 13

liver isoform of hexokinase

Answer 13

HKIV (higher Km); low affinity for glucose and not inhibited by glucose-6-phosphatase

Question 14

muscle isoform of hexokinase

Answer 14

HKI (lower Km); high affinity for glucose but readily inhibited by glucose-6-phosphatase; if TCA stops in anaerobic conditions, glucose-6-phosphate builds up so hexokinase activity slows down

Question 15

why do the different isoforms of hexokinase exist

Answer 15

if high [glucose-6-phosphate], HKI inhibited and HKIV is not, so more glucose converted to glucose-6-phosphate in liver, lowering [blood glucose]

Question 16

diagram of glucose metabolism by hexokinase isoforms in muscle, blood and liver

Answer 16

diagram

Question 17

graphs of liver and muscle hexokinase isoforms and corresponding glucose affinities

Answer 17

graphs