Oxidative phosphorylation is

Options

A. Formation of ATP by transfer of phosphate group from a substrate to ADP
B. Oxidation of phosphate group in ATP
C. Addition of phosphate group to ATP
D. Formation of ATP by energy releated from electrons removed during substrate oxidation

Answer

### Step-by-Step Solution:

1. **Understanding Oxidative Phosphorylation**:
- Oxidative phosphorylation is a metabolic pathway that produces ATP, the energy currency of the cell, through a series of reactions.

2. **Role of Electron Carriers**:
- In this process, electrons are transferred from electron carriers such as NADH and FADH2, which are generated during earlier stages of cellular respiration (like glycolysis and the Krebs cycle).

3. **Electron Transport Chain**:
- The electrons are passed through a series of proteins embedded in the inner mitochondrial membrane, known as the electron transport chain (ETC).

4. **Oxygen as the Final Electron Acceptor**:
- At the end of the electron transport chain, oxygen acts as the final electron acceptor, combining with electrons and protons to form water.

5. **ATP Formation**:
- The energy released during the transfer of electrons is used to pump protons across the mitochondrial membrane, creating a proton gradient. This gradient drives ATP synthesis via ATP synthase, a process known as chemiosmosis.

6. **Correct Answer Identification**:
- Among the given options, the correct definition of oxidative phosphorylation is: "formation of ATP by energy released from electrons removed during substrate oxidation."