Oxidative phosphorylation (L4)

Question 1

How many protons are translocated into the intermembrane space from the matrix per 2 e^-?

Answer 1

10H⁺

Question 2

What are the 3 major ETC complexes and rxns are they involved in?

Answer 2

Complex I: NADH-CoQ reductase (releases 4H⁺)

NADH→NAD as CoQ→CoQH₂

Complex III: cytochrome c reductase (4H+)

CoQH2→CoQ as cyto c(Fe³⁺)→cyto c(Fe²⁺)

Complex IV: cytocrome c oxidase (2H+)

cyto c(Fe²⁺)→cyto c(Fe³⁺) as 1/2O₂→H₂O

Question 3

What are 3 complexes that transfer electons to CoQ without transloacting protons?

Answer 3

Complex II: Succinate DH (no H+)

Succinate→fumarate as CoQ→CoQH2

Fatty acylCoA DH (ß oxidation)

E-FADH₂→E-FAD as CoQ→CoQH2

**Glycerol 3 P DH (shuttle) **

Glycerol-3-P→DHAP as CoQ→CoQH2

NOTE: These are all located before complexes III&IV so 6H⁺ are transloacted b/c of those 2 complexes. ALSO The first 2 are located on the matrix side of the inner membrane while Glycerol3PDH is located on intermembrane space side of the inner membrane

Question 4

NADH yields _ translocated protons and _ ATP.

FADH₂ yields _ translocated protons and _ ATP.

Answer 4

10, about 3 ATP;

6, about 2 ATP

Question 5

What does ADP/ATP translocase do?

What inhibits this transporter protein?

Answer 5

It translocates an ATP^-3 to the intermembrane space while it translocates an ADP^-2 to the matrix. By doing this it consumes the equivalent of 1 H⁺ of the gradient across the membrane.

Thus the energy required for ATP translocation reduces the overal ATP yield.

Atractyloside inhibits.

Question 6

Name the respiratory chain inhibitors, and an ATP synthase inhibitor.

Answer 6

I NADH-CoQ reducase: rotenome, amytal, metformin

II cytocrome c reductase: antimycin A

IV: cytochrome oxidase: cyanide, carbon monoxide

ATP synthase: oligomycin (not used clinically)