Chemicals taking part in respiratory electron transport are

Options

A. Flavin nucleotides
B. FeS and CoQ
C. Cytochromes
D. All the above

Answer

### Step-by-Step Solution:

1. **Understanding the Electron Transport Chain (ETC)**: The electron transport chain is a series of protein complexes and other molecules that transfer electrons from electron donors to electron acceptors via redox reactions. This process is crucial for cellular respiration and occurs in the inner mitochondrial membrane.

2. **Identifying Key Components**: The main chemicals involved in the electron transport chain include:
- **Cytochrome C**: A small heme protein that transfers electrons between complexes.
- **Ubiquinone (Coenzyme Q)**: A lipid-soluble electron carrier that transports electrons from complex I and II to complex III.
- **FMN (Flavin Mononucleotide) and FAD (Flavin Adenine Dinucleotide)**: These are coenzymes that participate in redox reactions.
- **Iron-Sulfur Proteins**: These proteins play a vital role in electron transfer.
- **Cytochrome Oxidase**: The enzyme complex that catalyzes the final step of the electron transport chain, transferring electrons to oxygen.

3. **Complexes of the Electron Transport Chain**: The components are organized into four main complexes:
- **Complex I (NADH Dehydrogenase)**: Accepts electrons from NADH.
- **Complex II (Succinate Dehydrogenase)**: Accepts electrons from FADH2.
- **Complex III (Cytochrome bc1 Complex)**: Transfers electrons from ubiquinone to cytochrome c.
- **Complex IV (Cytochrome Oxidase Complex)**: Transfers electrons to molecular oxygen, forming water.

4. **ATP Synthase**: Although not part of the electron transport chain itself, ATP synthase (Complex V) utilizes the proton gradient created by the electron transport chain to synthesize ATP.

5. **Conclusion**: All the mentioned chemicals and complexes are integral to the functioning of the respiratory electron transport chain. Therefore, the answer to the question is that all of the above components are involved in the electron transport chain.

### Final Answer:
The chemicals taking part in the respiratory electron transport chain are: **Cytochrome C, Ubiquinone, FMN, FAD, Iron-sulfur proteins, and Cytochrome oxidase**. Thus, the answer is **all of the above**.

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