Unit 1: Anaerobic respiration (energy from food without oxygen)

Question 1

what is the NHS daily energy requirement for women and men?

Answer 1

Women= 2000 kCal/ 8400 kJ
Men = 2500 kCal/ 10500 kJ

Question 2

what are glucose transporters?

Answer 2

transmembrane proteins which facilitate diffusion of glucose into cells

Question 3

where are the five types of glucose transporters found and what is their function?

Answer 3

GLUT1: all tissue - basal rate of uptake
GLUT2: liver/ pancreatic- glucose sensor - simulates insulin secretion
GLUT3: all tissue - basl rate of uptake in neurons
GLUT4: muscle/ fat - stimulates insulin secretion which facilitates uptake of glucose during meals
GLUT5: small intestine - fructose uptake

Question 4

what happens in terms of GLUT 4 when you do more exercise?

Answer 4

• expression increases in muscle/fat

- faster response to insluin

Question 5

what type of carrier proteins are glucose transporters and how do they work?

Answer 5

• symporters: transport Na+ and glucose simultaenously

- secondary active transport: use electrochemical gradient

Question 6

what type of cells only use glycolysis as source of ATP and give examples

Answer 6

• cells with no/ few mitochondria

red blood cells/ cornea & lenses of eye/ renal medulla

Question 7

what are the main 4 stages of glycolysis and how many steps in each?

Answer 7

• investment stage (3)
• splitting stage (2)
• yield stage (1)
• substrate level phosphorylation (4)

Question 8

how many ATP are invested to prime glucose metabolism?

Answer 8

2

Question 9

what is the first regulatory step in glycolysis?

Answer 9

• phosphoryl transfer - production of glucose-6-phosphate
  = regulatory enzyme: hexokinase
• allosterically inhibited by its product

Question 10

how does liver contribute to production of glucose 6- phosphate?

Answer 10

liver possess glucokinase which directly converts glycogen into glucose -6 phosphate and is not allosterically inhibited

Question 11

what is the most important regulatory (rate limiting) step also found in the investment stage?

Answer 11

phosphoryl transfer of fructose 6 phosphate to fructose 1,6 phosphate
IRREVERSIBLE REACTION

Question 12

How does the rate limiting step regulate rate of glycolysis?

Answer 12

Adenylate control: PFK allosterically inhibited by ATP - causes conformational change reducing affinity for Fru-6-P so reduces rate of reaction and glycolysis

Question 13

what activates/ inhibits PFK?

Answer 13

AMP = allosterically activates PFK - prevents ATP inhibition

citrate/ pH/ ATP inhibits

Question 14

what molecule is an important allosteric activator of PFK

Answer 14

Fructose 2,6 - biphosphate formed from fru6P by PFK2
- fru 6P accelerates formation of it which activates PFK1 so feed-forward activation occurs (accelerates its own metabolism)

Question 15

how is the first ATP produced in substrate level phosphorylation?

Answer 15

phosphoryl transfer of 1,3bisP-glycerate to 3P-glycerate by enzyme phosphoglycerate kinase

Question 16

how is the second ATP produced in substrate level phosphorylation?

Answer 16

phosphoryl transfer of PEP (phosphoenolpyruvate) to pyruvate by the enzyme pyruvate kinase

Question 17

how is the last regulatory step regulated?

Answer 17

• adenylate control
• down regulation of alanin
• up regulation by fru 1,6 BP

Question 18

how does liver prevent glucose conversion into pyruvate?

Answer 18

isoenzyme regulated by AMP converts glucose into glycogen instead

Question 19

what is the net energy yield of glycolysis?

Answer 19

2 ATP per mole of glucose

Question 20

what is lactic acid fermentation?

Answer 20

reduction of pyruvate by lactate dehydrogenase

Question 21

what is the important of lactate? and what are its physiological effects?

Answer 21

• gets rid of NADH so allows anaerobic respiration to continue
• muscle fatigue to prevent extreme exhaustion/ reduced oxygen-carrying ability

Question 22

where does the substrate cycle occur?

Answer 22

in liver

Question 23

what happens when glucose is abundant in terms of substrate cycle?

Answer 23

Fru 6P (insulin) activates phosphoprotein phosphatase) - dephosphorylates PFK2 catalyses conversion of fru 6P to Fru 2,6 BP upregulates PFK1 (downregulates gluconeogenesis)

Question 24

what happens when glucose is scarce - no insulin present in terms of substrate cycle?

Answer 24

glucagon activates PKA activates FBPase 2 Fru 2.6 BP to Fru 6P (downregulation of glycolysis - upregulation of gluconeogenesis)