During passage of electron over ETC.

Options

A. Electron undergoes resonance
B. Electron undergoes fluorescence
C. Electron undergoes active transport
D. pH of matrix increases.

Answer

### Step-by-Step Text Solution:

1. **Understanding Electron Transport Chain (ETC)**: The Electron Transport Chain (ETC) is a series of protein complexes located in the inner mitochondrial membrane that facilitates the transfer of electrons derived from NADH and FADH2.

2. **Location of ETC**: The ETC occurs in the mitochondria, which are known as the "powerhouses of the cell" because they generate ATP, the energy currency of the cell.

3. **Structure of Mitochondria**: Mitochondria have a double membrane structure:
- **Outer Membrane**: Smooth and permeable to small molecules.
- **Inner Membrane**: Highly folded into structures called cristae, which increase the surface area for the ETC.

4. **Components of ETC**: The ETC consists of four main protein complexes (Complex I to IV) and mobile electron carriers. Electrons are transferred through these complexes.

5. **Energy Release During Electron Transfer**: As electrons move through the ETC, they release energy. This energy is not used to produce ATP directly but is used to pump protons (H+) from the mitochondrial matrix into the intermembrane space (perimitochondrial space).

6. **Proton Pumping and pH Changes**: The pumping of protons from the matrix to the intermembrane space leads to a decrease in proton concentration in the matrix. Consequently, the pH of the matrix increases (becomes more alkaline).

7. **Conclusion**: Therefore, during the passage of electrons over the ETC, the pH of the mitochondrial matrix increases due to the reduction in proton concentration.