Question

In mitochondria, protons accumulate in _________.

• A. outer membrane
• B. inner membrane
• C. intermembrane space
• D. matrix

Answer 1

The correct option is C intermembrane space

During cellular respiration, protons accumulate in the intermembrane space of mitochondria.

The carriers i.e., $NADH+H^{+}$ and $FAD{H}_2$ get oxidised and release electrons which get transferred to the electron transport chain which in turn transfers electrons to oxygen through a series of electron carriers. The energy available in the electrons is used to pump the protons from the matrix to the intermembrane space. These protons get accumulated in the intermembrane space. This increases the concentration of protons in the intermembrane space as compared to the matrix.

During chemiosmosis, these protons return to the matrix through the ATP synthase complex. The energy in protons is utilised by ATP synthase to combine ADP and inorganic phosphate and thus ATP is formed.