How many protons are accumulated in intermembrane space of mitochondria from one molecule of NADH during ETS?

Options

A. Two
B. Three
C. Four
D. Six

Explanation

To determine how many protons are accumulated in the intermembrane space of mitochondria from one molecule of NADH during the electron transport system (ETS), we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Role of NADH in ETS**:
- NADH is a key electron carrier in cellular respiration. It donates electrons to the electron transport chain (ETC), which is located in the inner mitochondrial membrane.

2. **Identify the Starting Point**:
- When NADH donates electrons, it is oxidized to NAD+. This process occurs at Complex I (NADH dehydrogenase) of the electron transport chain.

3. **Electron Transport Chain (ETC) Overview**:
- The ETC consists of several complexes (Complex I, II, III, and IV) that facilitate the transfer of electrons. As electrons move through these complexes, they release energy.

4. **Proton Pumping Mechanism**:
- The energy released during the electron transfer is used to pump protons (H+) from the mitochondrial matrix into the intermembrane space. This creates a proton gradient.

5. **Quantify Proton Accumulation**:
- For each molecule of NADH that enters the electron transport chain, approximately 10 protons are pumped into the intermembrane space. This occurs as follows:
- Complex I pumps 4 protons.
- Complex III pumps 4 protons.
- Complex IV pumps 2 protons.
- Therefore, the total is 4 + 4 + 2 = 10 protons.

6. **Conclusion**:
- From one molecule of NADH, a total of **10 protons** are accumulated in the intermembrane space during the electron transport system.

### Final Answer:
**10 protons are accumulated in the intermembrane space of mitochondria from one molecule of NADH during ETS.**

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