Evaluating The Evidence For Chemiosmosis

Question 0

Explain why no ATP is made in mitoblasts (mitochondria stripped of outer membrane)

Answer 0

• there is no inter membrane space so H+ ions/protons are not trapped so they do not build up
• so there is no gradient formed and a gradient is needed to make ATP

Question 1

Explain why there is a lower pH in the intermembrane space

Answer 1

• inner membrane is impermeable as H+ ions are accumulating
• there is a potential difference across the membrane and the matrix as a loss of H+ from the matrix makes it more negative, a gain of H+ in the intermembrane space makes it more positive

Question 2

Explain why there is no ATP made in the presence of oligomycin (binds to ATP synthase, blocking the channel)

Answer 2

• H+ ions cannot flow down the gradient through the ATP synthase channel
• so they cannot produce a proton motive force –> this showed that the flow of H+ ions through ATP synthase was needed to make ATP

Question 3

Explain why no ATP is made of the head pieces are removed from the stalked particles

Answer 3

• if there is no heads the cannot rotate under proton motive force to phosphorylate ADP + Pi –> heads make ATP