Main source of ATP in a cell is by oxidative phosphorylation is

Options

A. Glycolysis
B. ETS
C. Krebs cycle
D. Pyruvate oxidation

Answer

### Step-by-Step Text Solution:

1. **Understanding Oxidative Phosphorylation**:
- Oxidative phosphorylation is the final stage of cellular respiration where ATP is produced. It occurs in the mitochondria of the cell.

2. **Role of Electron Transport Chain (ETC)**:
- The process involves the transfer of electrons from electron carriers, specifically NADH and FADH2, to molecular oxygen (O2). This transfer occurs through a series of protein complexes known as the electron transport chain (ETC).

3. **Formation of ATP**:
- As electrons move through the ETC, they release energy. This energy is used to pump protons (H+) from the mitochondrial matrix into the intermembrane space, creating a proton gradient.

4. **Chemiosmosis**:
- The protons then flow back into the mitochondrial matrix through ATP synthase, a protein that synthesizes ATP from ADP and inorganic phosphate (Pi). This process is known as chemiosmosis.

5. **Conclusion**:
- Therefore, the main source of ATP in a cell during oxidative phosphorylation is the electron transport system (ETS), which facilitates the transfer of electrons and the subsequent production of ATP.