No cell can live without

Options

A. Chloroplasts
B. Proteins
C. Enzymes
D. Phytochrome.

Answer

To answer the question "No cell can live without," we will analyze each option provided and determine which one is essential for all cells.

### Step-by-Step Solution:

1. **Analyze the first option: Chloroplasts**
- Chloroplasts are organelles found primarily in green plants and certain photosynthetic bacteria. They are responsible for photosynthesis, converting sunlight into energy.
- **Conclusion**: Not all cells have chloroplasts (e.g., animal cells), so this option is incorrect.

2. **Analyze the second option: Proteins**
- Proteins are essential biomolecules made up of amino acids. They play a crucial role in various cellular functions, including structural support, transport, and catalyzing biochemical reactions.
- **Conclusion**: Proteins are necessary for almost all cell functions, making this option likely correct.

3. **Analyze the third option: Enzymes**
- Enzymes are a specific type of protein that act as biocatalysts to speed up chemical reactions in the cell. While they are important, not all cells require enzymes to survive, as some basic cellular functions can occur without them.
- **Conclusion**: This option is incorrect because cells can survive without enzymes.

4. **Analyze the fourth option: Phytochromes**
- Phytochromes are pigments that act as photoreceptors, primarily found in plants. They are involved in detecting light and regulating plant growth.
- **Conclusion**: Like chloroplasts, phytochromes are not present in all cells (e.g., animal cells), making this option incorrect.

5. **Final Conclusion**:
- After analyzing all options, the only essential component for all cells is **proteins**. Therefore, the correct answer is **B: proteins**.