Ions pile up on the side the pump sends them to
- The idea
- Predict
- See it
- Why
- Check
The idea
“The electron transport chain pumps H+ into the matrix, so that's where H+ collects.”
The matrix is where the citric acid cycle makes NADH, so it seems like the place H+ would gather. The chain sends H+ out of it.
The short version
The mistake: The electron transport chain pumps H+ into the matrix, so that's where H+ collects.
What's actually true: The chain pumps H+ out of the matrix into the intermembrane space, which ends up with more H+ and a lower pH.
- A pump spends energy to move an ion against its gradient. The ion piles up on the side the pump sends it to.
- The chain pumps H+ from the matrix into the intermembrane space. In chloroplasts, a similar chain pumps H+ from the stroma into the thylakoid lumen.
- ATP synthase is the way back. H+ flows down its gradient through it, and that flow makes ATP.
On the exam: Ask where the pump sends the ion. That side gets crowded.