In the electron transport system present in the inner mitochondrial membrane complexes I and IV are respectively

Options

A. NADH dehydrogenase and `FADH_(2)`
B. `FADH_(2)` and `NADH` dehydrogenase
C. `NADH` dehydrogenase and cytochrome c oxidase complex
D. NADH dehydrogenase and ATP synthase

Explanation

To answer the question regarding the complexes I and IV in the electron transport system present in the inner mitochondrial membrane, we can break down the solution into the following steps:

### Step-by-Step Solution:

1. **Understanding the Electron Transport Chain (ETC)**:
- The electron transport chain is a series of protein complexes located in the inner mitochondrial membrane that facilitate the transfer of electrons derived from NADH and FADH2, which are produced during the Krebs cycle.

2. **Identifying Complex I**:
- Complex I is known as **NADH dehydrogenase**. Its primary function is to accept electrons from NADH (which is oxidized to NAD+) and transfer them to ubiquinone (coenzyme Q). This process also contributes to the pumping of protons (H+) from the mitochondrial matrix into the intermembrane space, creating a proton gradient.

3. **Identifying Complex IV**:
- Complex IV is known as **cytochrome c oxidase**. This complex is responsible for transferring electrons from cytochrome c to molecular oxygen (O2), which is the final electron acceptor in the chain. This process also involves the reduction of oxygen to water (H2O) and contributes to the proton gradient by pumping protons into the intermembrane space.

4. **Summarizing the Complexes**:
- Therefore, in the context of the question, Complex I is **NADH dehydrogenase** and Complex IV is **cytochrome c oxidase**.

### Final Answer:
- Complex I: NADH dehydrogenase
- Complex IV: Cytochrome c oxidase