Lecture 31: Oxidative phosphorylation

Question 1

How much ATP is made for every 4 protons pumped?

How much NADH is made from 10 protons pumped?

How much FAH2 is made form 6 protons pumped?

Answer 1

= 1 ATP made for every 4 protons pumped

NADH = 10 protons pumped, 2.5 ATP made
FADH2 = 6 protons pumped, 1.5 ATP made

Question 2

How does ATP synthase work?

- describe ATP synthase

Answer 2

• the rotor subunits turn
• the stator subunits do not turn
• proton flow drives rotor movement
• rotor movement causes conformation changes in the stator that drives ATP synthase
  F1 is in the matrix
  FO is in the IMM

Question 3

What is proton motive force?

Answer 3

• a chemical gradient or pH gradient as a result of different H+ concentrations on either side of the membrane
• an electrical gradient as a result of the charge difference across the membrane

The ETC produces a proton gradient used by ATP synthase to make ATP

Question 4

What is the chemiosmotic theory?

• what are its main features

Answer 4

• inner membrane is impermeable to protons
• the ECT pumps protons out of the matrix
• the proton gradient created drives ATP synthesis

Question 5

What is the main evidence that supports the chemiosmotic theory?

Answer 5

• Treat mitochondria with detergent to remove outer membrane - the ETC still works but no ATP generation as there is no gradient
• ATP can also be made by an artificial liposome with a light-inducible proton pump and an ATP synthase but no ETC

Question 6

What is the role of “uncouplers” in oxidative phosphorylation?

Answer 6

Uncouplers can stop ATP synthesis - but the ETC is unaffected
- Dinitrophenol DNP can shuttle H+ from the inter membrane space to the matrix this dissipating the proton gradient
= proton gradient is required to make ATP
= the proton motive force is necessary for ATP synthesis