Where each stage of respiration happens
- The idea
- Predict
- See it
- Why
- Check
The idea
“The Krebs cycle happens between the two mitochondrial membranes, where all the protons are.”
The proton gradient builds between the membranes, so it's easy to think the main stages run there too. And four compartments are easy to mix up.
The short version
The mistake: The Krebs cycle happens between the two mitochondrial membranes, where all the protons are.
What's actually true: In eukaryotes, glycolysis runs in the cytosol, Krebs in the matrix, and the ETC and ATP synthase in the inner membrane.
- Glycolysis needs no mitochondria, so red blood cells, which have none, still run it.
- The matrix is the fluid inside the inner membrane. The Krebs cycle there loads electrons onto NADH and FADH2.
- The inner membrane, folded into cristae, holds both the electron transport chain and ATP synthase.
On the exam: Glycolysis is in the cytosol, Krebs in the matrix, the ETC and ATP synthase in the inner membrane.