A scientist treats chloroplasts with a chemical that makes the thylakoid membrane leak protons…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A scientist treats chloroplasts with a chemical that makes the thylakoid membrane leak protons. Light still falls on them, and electrons still move along the chain. (a) What happens to the proton gradient? (b) What happens to the making of ATP, and why? (c) On which side of the membrane is ATP normally made? (d) Which part of ATP synthase makes it?
Need a reminder? The key ideaShow
Chemiosmosis: a membrane, a proton pump, a proton gradient and ATP synthase. Protons collect in the lumen (water splitting, the carrier that moves protons across, and NADP reductase using stroma protons). ATP synthase: CF0 is a channel in the membrane, CF1 sticks into the stroma and makes ATP. Each pH unit is a factor of ten in the proton concentration. The ATP and NADPH go to the stroma.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. The gradient. The protons leak back across the membrane, so the gradient cannot build up.
Step 2. The ATP. ATP is made by the flow of protons through ATP synthase. When protons leak by another way, the flow through CF0 falls and less ATP is made, even though the electrons still move.
Step 3. The side. ATP is made on the stroma side.
Step 4. The part. The part that makes ATP is CF1, the head that sticks into the stroma.
Answer: (a) it is lost; (b) ATP making falls, because no gradient drives ATP synthase; (c) the stroma side; (d) CF1.
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