As per chemiosmotic coupling hypothesis, in mitochondria, protons accumulate in the

Options

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

Explanation

### Step-by-Step Text Solution:

1. **Understanding the Chemiosmotic Coupling Hypothesis**: The chemiosmotic coupling hypothesis was proposed by Peter Mitchell, who won the Nobel Prize for this work. It explains how ATP is produced in mitochondria.

2. **Role of NADH and FADH2**: During cellular respiration, NADH and FADH2 are produced from glycolysis and the Krebs cycle. These molecules are crucial as they enter the electron transport chain (ETC) in the mitochondria.

3. **Proton Transport**: In the electron transport chain, NADH and FADH2 donate electrons, which leads to the pumping of protons (H⁺ ions) from the mitochondrial matrix across the inner mitochondrial membrane into the intermembrane space. This creates a proton gradient.

4. **Accumulation of Protons**: As protons are pumped into the intermembrane space, they accumulate there, creating a higher concentration of protons compared to the matrix.

5. **ATP Formation**: The protons then flow back into the matrix through ATP synthase (F0 complex), which is embedded in the inner mitochondrial membrane. This flow of protons drives the synthesis of ATP from ADP and inorganic phosphate (Pi).

6. **Conclusion**: Therefore, according to the chemiosmotic coupling hypothesis, protons accumulate in the **intermembrane space** of the mitochondria.

### Final Answer:
Protons accumulate in the **intermembrane space** of the mitochondria.

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