metabolic pathways and ATP production

Question 1

where does oxidative decarboxylation (link reaction) occur

Answer 1

mitochondria

Question 2

oxidative decarboxylation reaction

Answer 2

pyruvate + HSCoA → acetyl CoA + CO2; NAD+ → NADH + H+

Question 3

pyruvate dehydrogenase complex: enzymes

Answer 3

pyruvate decarboxylase, lipoamide reductase-transacetylase, dihydrolipoyl dehydrogenase

Question 4

pyruvate dehydrogenase complex: cofactors

Answer 4

[1] TPP (from vitamin B1 thiamine; bound to pyruvate decarboxylase), [2] lipoamide (bound to lipoamide reductase-transacetylase), [3] FAD (bound to dihydrolipoyl dehydrogenase), [4] CoA, [5] NAD+

Question 5

oxidative decarboxylation pathway

Answer 5

pyruvate → hydroxyethyl TPP + CO2 [1]; hydroxyethyl TPP → acetylipoamide [2]; acetyl + CoA → acetyl CoA [4]; regenerate oxidised lipoamide (+FADH2) [3]; regenerate oxidised FAD (+NADH) [5]

Question 6

where does the TCA cycle occur

Answer 6

mitochondrial matrix

Question 7

is TCA aerobic or anaerobic

Answer 7

aerobic - NAD+ is only regenerated in oxidative phosphorylation

Question 8

structure of acetyl CoA

Answer 8

high energy C-S (thioester) bond, acetyl, adenine and ribose groups

Question 9

TCA intermediates (can I keep selling sex for money officer)

Answer 9

citrate, isocitrate, a-ketoglutarate, succinyl CoA, succinate, fumarate, malate, oxaloacetate

Question 10

TCA: first step

Answer 10

oxaloacetate + acetyl CoA → citrate; transfer acetyl by hydrolysing C-S bond; catalysed by citrate synthase

Question 11

TCA: second and third steps

Answer 11

isomerised to isocitrate then oxidised to a-ketoglutarate by isocitrate dehydrogenase (NAD+ → NADH + H+); + CO2

Question 12

TCA: fourth step

Answer 12

converted to succinyl CoA by addition of HSCoA (similar to PDH complex); catalysed by a-ketoglutarate dehydrogenase (NAD+ + NADH + H+); + CO2

Question 13

TCA: fifth step

Answer 13

hydration to succinate where CoA is displaced by PO4 3- by succinyl CoA synthetase; GDP + Pi → GTP (substrate-level phosphorylation)

Question 14

TCA: sixth step

Answer 14

oxidation to fumarate by succinate dehydrogenase in membrane (for e- transport; FAD → FADH2)

Question 15

TCA: seventh and eighth steps

Answer 15

hydration to form malate then oxidised to form oxaloacetate by malate dehydrogenase (NAD+ → NADH + H+)

Question 16

what is GTP used for

Answer 16

used in signal transduction

Question 17

where is ATP used instead

Answer 17

skeletal and cardiac muscle

Question 18

net yield of TCA

Answer 18

3 NADH, 1 FADH2, 1 GTP

Question 19

diagram of TCA cycle

Answer 19

diagram from metabolism 4

Question 20

what is the maximum yield of ATP

Answer 20

12 - 3 ATP per NADH (so 9); 2 ATP per FADH2 (so 2) and 1 GTP

Question 21

products of amino acid degradation

Answer 21

amino → urea, carbon → produce glucose

Question 22

glucogenic amino acids

Answer 22

enter TCA to become glucose

Question 23

ketogenic

Answer 23

become acetyl CoA

Question 24

transamination general formula

Answer 24

keto acid 1 + amino acid 1 → amino acid 2 + keto acid 2

Question 25

transamination with alanine as an example

Answer 25

a-ketoglutarate + alanine → glutamate + pyruvate

Question 26

what enzyme catalysed alanine transamination

Answer 26

alanine aminotransferase

Question 27

fate of pyruvate

Answer 27

becomes acetyl CoA by PDH

Question 28

fate of glutamate

Answer 28

a-ketoglutamate and NH4+ (converted to urea)

Question 29

high levels of alanine transferase is a marker for which disease

Answer 29

hepatitis C

Question 30

why do catabolic reactions use NADH and anabolic reactions use NADPH

Answer 30

to seperate electron transport