# Explain the role of the mitochondrial inner membrane in the production of ATP during aerobic cell respiration.

> IB DP Biology Standard Level (2023 syllabus) — C1.2 Cell respiration · Explain · 4 marks

## Mark scheme (4 marks)

1. The inner mitochondrial membrane contains electron carriers / the electron transport chain
2. Electrons are passed along the carrier proteins, releasing energy that is used to actively pump protons (H⁺) from the matrix into the intermembrane space
3. A proton / electrochemical gradient is established across the inner membrane
4. Protons flow back into the matrix through ATP synthase, and this drives the synthesis of ATP from ADP and inorganic phosphate

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