Which of the following is a fibrous protein?

Options

A. albumin
B. globulin
C. glutelin
D. actin

Answer

To determine which of the following is a fibrous protein, we need to understand the classification of proteins based on their structure. Proteins can be categorized into two main types: fibrous proteins and globular proteins.

### Step-by-Step Solution:

1. **Understanding Protein Classification**:
- Proteins are classified into two types: fibrous and globular.
- Fibrous proteins are long, thread-like structures that provide support and strength, while globular proteins are more compact and rounded.

2. **Identifying the Options**:
- The question presents several options, and we need to analyze each one to determine its classification.
- Common examples of proteins include albumin, globulins, glutulin, and actin.

3. **Analyzing Each Option**:
- **Albumin**: This is a globular protein found in blood plasma, involved in osmoregulation.
- **Globulins**: Another type of globular protein, associated with immune functions (immunoglobulins).
- **Glutulin**: A storage protein found in wheat, also classified as globular.
- **Actin**: This is a fibrous protein that plays a crucial role in muscle contraction.

4. **Conclusion**:
- Among the options provided, actin is the only fibrous protein. Therefore, the correct answer is option number four: **Actin**.

### Final Answer:
**Actin is a fibrous protein.**