Link, Krebs And ECT

Question 1

What enzyme catalyses the reaction of pyruvate to acetyl coA in the link reaction?

Answer 1

pyruvate dehydrogenase

Question 2

other than acetyl coA, what else is produced in the link reaction?

Answer 2

CO2, NADH

Question 3

Where does link reaction occur?

Answer 3

matrix of mitochondria

Question 4

What would be the result of a pyruvate dehydrogenase deficiency?

Answer 4

lactic acidosis

Question 5

What inhibits and activates pyruvate dehydrogenase?

Answer 5

inhibits:
- ATP
- NADH
- citrate
- acetyl coA
activates:
- AMP
- NAD
- ADP
- insulin
- pyruvate

Question 6

acetyl coA combines with what to create what in the first step of the krebs cycle?

Answer 6

acetyl CoA combines with oxaloacetate to create citrate

Question 7

What enzyme reduces iscocitrate (6C) to a 5C intermediate (a ketogluterate) and what is produced in this reaction?

Answer 7

isocitrate dehydrogenase
CO2
NADH

Question 8

What enzyme converts the 5C intermediate a- ketogluterate to a 4C intermediate with a coA attached and what is produced in this reaction?

Answer 8

a- ketogluterate dehydrogenase

NADH and CO2

Question 9

There are 4, 4C intermediates before oxaloacetate. For each of the 4 reactions, state what is produced.

Answer 9

1st reaction- GTP and coA
2nd- FADH2
3rd- H20
4th- NADH

Question 10

What substances inhibit isocitrate dehydrogenase and a- ketogluterate dehyrdogenase and what activates isocitrate dehyrdogenase?

Answer 10

inihibits- ATP, NADH (succinyl CoA also inhibits aketogluterate dehydrogenase by feedback inihbition)
activates- ADP (isocitrate dehydrogenase only)

Question 11

What the electron carriers in the ECT called?

Answer 11

PTC1,2 and 3 (proton translocator complexes)

Question 12

What is the conc gradient of H+ created by the ETC called?

Answer 12

proton motive force

Question 13

What is the name of the membrane protein that creates ATP from the diffusion of H+ back into the matrix?

Answer 13

proton translocating ATPase or ATPsynthase

Question 14

What type of phosphylation occurs in the ETC?

Answer 14

oxidative phosphorylation

Question 15

Can ATP synthase be used to create a conc graident of H+?

Answer 15

Yes it can reverse to actively transport H+ up a conc gradient

Question 16

How to CN- and CO inhibit the ETC?

Answer 16

They bind to the haem group on the terminal PTC so O2 cannot accept terminal electrons from the ETC

Question 17

How do uncouplers decrease the amount of ATP created by the ETC?

Answer 17

They increase permeability of H+ so H+ can diffuse back into the matrix without passing back through ATPsynthase.

Question 18

Give 2 examples of uncouplers

Answer 18

fatty acids
dinitrophenol (in weightloss tablets, pesticides)
thermogenin (in brown adipose tissue)

Question 19

How does brown fat create more heat when cold or noradrenaline released?

Answer 19

• lipase is activated so fatty acids are produced from triglycerides
• Fatty acids activate thermogenin (UCP1) and increase the ETC
• UCP1 uncouples, H+ moves back without passing through ATPsynthase to create more heat than ATP

Question 20

What are differences between oxidative and substrate level phosphylation?

Answer 20

oxidative:

• uses membrane associated complexes (not soluble)
• uses proton gradient (not direct energy from po4 bond)
• cannot occur w/out O2
• creates most of the ATP