TCA cycle and ETC

Question 1

what is the pyruvate dehydrogenase complex made up of?

Answer 1

it’s made up of 3 different enzymes

E1, E2. E3

Question 2

what is enzyme E1?

Answer 2

pyruvate dehydrogenase

Question 3

what reaction is catalysed by E1?

Answer 3

TPP being added to pyruvate to make acyl-TPP

Question 4

what is enzyme E2?

Answer 4

dihyrolipoamide acyltransferase

Question 5

what reaction is catalysed by E2?

Answer 5

lipoamide arm replaces the TPP to form acyl-lipoate

Question 6

what is enzyme E3?

Answer 6

Dihydrolipoyl dehydrogenase

Question 7

what reaction is catalysed by E3?

Answer 7

Regenerate lipoamide arm through the reduction of FAD to FADH

Question 8

what vitamin is TPP derived from?

Answer 8

vitamin B1

Question 9

what is PDC controlled by?

Answer 9

feedback inhibition - when acetyl coA and NADH levels are high, the enzyme is inhibited
covalent modification - phosphorylation

Question 10

what effect does phosphorylation have on PDC?

Answer 10

activates it

Question 11

what effect does insulin have on PDC?

Answer 11

dephosphorylation - activates glucose metabolism

Question 12

where does the TCA cycle occur?

Answer 12

mitochondrial matrix

Question 13

what process forms GTP in the TCA cycle?

Answer 13

substrate level phosphorylation

Question 14

what are reduced coenzymes used for?

Answer 14

oxidised and feed electrons into the ETC
ETC uses these electrons to pump protons across the mitochondrial membrane
produces ATP

Question 15

explain what each of the 4 complexes does in the ETC?

Answer 15

1 - 2 electrons removed from NADH to UQ
2 - FADH2 - electrons transferred to UQ
3 - UQ to cytochrome C
4 - electrons removed from cytochrome C to combine with O2 –> H2O

Question 16

what substances inhibit the ETC

Answer 16

carbon monoxide

cyanide

Question 17

what complex do CO and cyanide inhibit and what effect does this have?

Answer 17

complex 4 - causes a backlog of electrons

Question 18

what is coupling?

Answer 18

using the proton gradient to make ATP

how the ETC and oxidative phosphorylation are coupled by a proton gradient across the inner mitochondrial membrane

Question 19

what is uncoupling?

Answer 19

using the energy from the ETC in other processes

Question 20

how can uncoupling occur?

Answer 20

removing the proton gradient

equalising the charges on either side –> removing the charge gradient

Question 21

what is non-shivering thermogenesis?

Answer 21

process by which babies keep warm and how we keep warm without shivering

Question 22

what is thermogenin?

Answer 22

uncoupling protein 1 - membrane channel

Question 23

how does non-shivering thermogenesis work?

Answer 23

thermogenin allows protons to flow through it and produce heat rather than ATP

Question 24

explain how Gramicidin works?

Answer 24

forms 2 half channels – neutralises the charge gradient and kills the bacteria

Question 25

explain how Nigericin works?

Answer 25

neutralises charge gradient and kills bacteria | protons can permeate the membrane

Question 26

explain how valinomycin works?

Answer 26

allows for dissipation of charge through movement of K+ across the membrane

Question 27

what is valinomycin used clinically?

Answer 27

eye drops

Question 28

what makes dinitro-phenol membrane soluble?

Answer 28

its negative charge is spread throughout the molecule

Question 29

what does dinitro-phenol do?

Answer 29

acts as a proton carrier across the mitochondrial membrane and neutralises the charge releases the energy as heat - makes you feel hot

Question 30

what are the problems with dinitro-phenol?

Answer 30

has a very close therapeutic between weight loss and death lethal dose not allowed

Question 31

what are the intermediates of the TCA used to make?

Answer 31

amino acids fatty acids steroids nucleotides

Question 32

how can the citrate of the TCA cycle be used?

Answer 32

turned into oxaloacetate and acetyl coA --> fatty acids and cholesterol

Question 33

what does the TCA rate depend on?

Answer 33

NAD+ availability --> depends on ETC rate --> linked to ATP:ADP ratio

Question 34

in muscle, what are dehydrogenases stimulated by?

Answer 34

calcium

Question 35

wat causes hypoxia?

Answer 35

altitude trauma exercise too much

Question 36

what complex of the ETC does hypoxia block?

Answer 36

complex 4

Question 37

how are ROS formed?

Answer 37

electrons flow near the surface of complex 1 when they build up, alternative electron routes start occurring ROS formed

Question 38

why are ROS bad for the cell?

Answer 38

react with things in the cell and damage them

Question 39

how can body limit the damage by ROS?

Answer 39

limit ATP by switching off non-essential cell functions improve anaerobic ATP production efficiency limit oxidative stress - providing protection against ischaemia

Question 40

explain what happens to HIF1a in normal and hypoxic conditions?

Answer 40

normal - HIF1a subunit is degraded | hypoxia - stabilised and binds to upstream elements of promoters

Question 41

what does HIF do and how does this reduce damage by ROS?

Answer 41

downregulates mitochondria respiration during hypoxia – promotes loss of mitochondria (autophagy) and suppresses biogenesis reduce no of mitochondria --> reduce no of ETC --> lower oxygen demand --> fewer ROS