Keratin is a .... ............ protein

Explanation

**Step-by-Step Solution:**

1. **Identify the Type of Protein:** The question asks about the type of protein that keratin is. To answer this, we need to understand the characteristics of keratin.

2. **Understand Keratin's Function and Structure:** Keratin is a protein that is primarily found in hair, nails, feathers, and horns. It serves a structural role in these biological materials.

3. **Differentiate Between Protein Types:** There are two main types of proteins: fibrous proteins and globular proteins. Fibrous proteins are typically long, strand-like structures that provide support and strength, while globular proteins are more compact and functional.

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