Krebs

Question 1

Reaction 1 of Krebs

1) what is it?
2) catalysed by?
3) highly exergonic or endo? and why?
4) How does the enzyme work in this reaction
5) reversble or ire?

Answer 1

1) Acetyl CoA and Oxaloacetate —> Citrate
2) Citrate synthase
3) Highly exergonic because a high energy thio-ester is hydrolysed
4) Oxaloacetate induces a large conformational change in the enzyme. This change allows the acetyl Co-A to then bind
5) irreversible

Question 2

Reaction 2 of Krebs

1) what is it?
2) how many steps?
3) catalysed by what?
4) reversible or irre?
5) the reaction favours what
6) what makes it go forward though?

Answer 2

1) Citrate to Isocitrate
2) 2 steps. Citrate to Cis Aconitate to Isocitrate
3) Aconitase
4) Reversible
5) Favours the formation of citrate, so the backward reaction
6) Isocitrate is consumed rapidly by the cycle so the forward reaction is driven

Question 3

Reaction 3 of Krebs

1) what is it?
2) catalysed by?
3) what are the byproducts?
4) what cofactor?
5) what is formed that is equal to 2.5ATP
6) The enzyme serves as what for the citric acid cycle

Answer 3

1) isocitrate to alpha-ketoglutarate
2) isocitrate dehydrogenase
3) NADH + H+ + CO2
4) Mn2+
5) NADH
6) 2nd control point

Question 4

Reaction 4 of Krebs

1) what is it
2) catalysed by what?
3) what does the answer from 2 mirror?
4) serves as what for the cycle?
5) Uses what?
6) byproducts?

Answer 4

1) Alpha Ketoglutarate –> Succinyl-CoA
2) Alpha ketoglutarate dehydrogenase complex
3) Mirrors the PDH complex in that it catalyses a 3,4,5 reaction
4) 3rd and final control point
5) CoA, NAD+
6) NADH and CO2

Question 5

Reaction 5 of Krebs

1) What is it?
2) Catalysed by what?
3) energy is released how and this is used to drive synthesis of what?

Answer 5

1) Succinyl-CoA to Succinate
2) Succinyl-CoA Synthetase
3) Energy release in the form of hydrolysis of a thioester bond that is used to drive the synthesis of GTP

Question 6

Reaction 6 of Krebs

1) What is it
2) catalysed by what?
3) utilises what as a cofactor so what does it also produce
4) the thing produced in 3 is equivalent to what?

Answer 6

1) Succinate to Fumarate
2) Succinate dehydrogenase
3) FAD as a cofactor so produces FADH2
4) 1.5 ATP

Question 7

Reaction 7 of Krebs

1) what is it?
2) catalysed by ?
3) what is the intermediate
4) what makes this enzyme very specific?

Answer 7

1) Fumarate to L-Malate via an intermediate
2) Fumarase
3) Carbanion transition state
4) Highly stereospecific so cannot bind or react with cis isomer of fumarate or the D malate isomer

Question 8

Reaction 8 of Krebs

1) What is it?
2) Catalysed by?
3) produces what and this is equivalent to?

Answer 8

1) L-malate to oxaloacetate
2) Malate dehydrogenase
3) NADH = 2.5ATP

Question 9

Look at overall ting on lecture 12

Answer 9

skeen