Name the process by which ATP is formed in electron transport system (ETS) in mitochondria.

Answer

**Step-by-Step Solution:**

1. **Understanding the Electron Transport System (ETS):**
The electron transport system is a series of protein complexes located in the inner membrane of the mitochondria. It plays a crucial role in cellular respiration, specifically in the production of ATP.

2. **Identifying the Process of ATP Formation:**
The process by which ATP is formed in the electron transport system is known as oxidative phosphorylation. This process is essential for aerobic respiration.

3. **Role of NADH and FADH2:**
NADH and FADH2 are the substrates that donate electrons to the electron transport chain. These molecules are generated during earlier stages of cellular respiration, such as glycolysis, the link reaction, and the Krebs cycle.

4. **Mechanism of Oxidative Phosphorylation:**
During oxidative phosphorylation, electrons are transferred through a series of protein complexes (usually four major complexes). As electrons move through these complexes, they release energy, which is used to pump protons (H+) across the inner mitochondrial membrane, creating a proton gradient.

5. **ATP Synthesis:**
The energy stored in the proton gradient is then used by ATP synthase, an enzyme that synthesizes ATP from ADP and inorganic phosphate (Pi) as protons flow back into the mitochondrial matrix.

6. **Final Products:**
The complete oxidation of substrates results in the formation of carbon dioxide and water, along with the release of ATP.

**Final Answer:**
The process by which ATP is formed in the electron transport system (ETS) in mitochondria is called **oxidative phosphorylation**.

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