Energy and Metabolism

ID #1083

Was the reason the H ions don't diffuse into the cytoplasm from the proton gradient because it's more basic inside the matrix, so they want to come back in? I was confused on how the cytoplasm acts as a buffer.

Actually, some of the protons DO go from the intermembrane space (IMS) into the cytoplasm. But you're right about what they'd "rather" do. Because of the uneven concentration, a given proton would like to come back into the matrix. My point about the "buffering" effect of the cytoplasm was to explain why the pH of the IMS doesn't keep getting lower and lower as the ETC moves more and more protons. Because some of those protons can float out into the cytoplasm, and others can float in, the pH of the IMS isn't going to drop noticeably compared to the pH of the cytoplasm. Instead, the pH of the matrix increases.

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