Which one of the following biomolecules is insoluble in water

Options

A. `alpha`-keratin
B. haemoglobin
C. ribonuclease
D. adenine.

Explanation

To solve the question "Which one of the following biomolecules is insoluble in water?" we will analyze each of the given options: alpha carotene, hemoglobin, ribonuclease, and adenine.

### Step-by-Step Solution:

1. **Understanding Biomolecules**:
- Biomolecules are categorized into carbohydrates, proteins, and lipids (fats).
- Proteins can be further divided into fibrous proteins and globular proteins.

**Hint**: Remember the classification of biomolecules and their solubility characteristics.

2. **Analyzing Alpha Carotene**:
- Alpha carotene is a type of carotenoid, which is a pigment and is classified as a fibrous protein.
- Fibrous proteins are typically insoluble in water.

**Hint**: Identify the type of biomolecule and its solubility properties.

3. **Analyzing Hemoglobin**:
- Hemoglobin is a globular protein that is soluble in water.
- Globular proteins usually have a compact structure and are soluble due to their hydrophilic side chains.

**Hint**: Distinguish between fibrous and globular proteins based on their solubility.

4. **Analyzing Ribonuclease**:
- Ribonuclease is also a globular protein and is soluble in water.
- It plays a role in the degradation of RNA and is soluble due to its structure.

**Hint**: Recall that ribonuclease is an enzyme and enzymes are typically globular proteins.

5. **Analyzing Adenine**:
- Adenine is a nitrogenous base and is also soluble in water.
- Nitrogenous bases are polar and tend to dissolve in water.

**Hint**: Remember that nitrogenous bases are generally water-soluble due to their polar nature.

6. **Conclusion**:
- After analyzing all the options, we find that alpha carotene is the only biomolecule listed that is insoluble in water.
- Therefore, the correct answer is **alpha carotene**.

### Final Answer:
- The biomolecule that is insoluble in water is **alpha carotene**.