Microtubules are made of

Options

A. Actin
B. Keratiin
C. Tubulin
D. Dyenin

Answer

### Step-by-Step Solution:

1. **Understanding Microtubules**: Microtubules are one of the three main components of the cytoskeleton in eukaryotic cells. They are known for providing structural support, shape, and facilitating cell division and movement.

2. **Identifying the Composition**: Microtubules are specifically made up of proteins. To determine what these proteins are, we need to look at the options provided.

3. **Analyzing the Options**:
- **Option 1: Actin** - This is a globular protein that forms microfilaments, not microtubules.
- **Option 2: Keratin** - This is a structural protein found in intermediate filaments, also not related to microtubules.
- **Option 3: Tubulin** - This is a globular protein that is the primary building block of microtubules.
- **Option 4: Dynein** - This is a motor protein that moves along microtubules but is not a component of microtubules themselves.

4. **Conclusion**: Based on the analysis, the correct answer is that microtubules are made up of **tubulin**. Tubulin consists of two subunits, alpha and beta tubulin, which polymerize to form protofilaments. Thirteen of these protofilaments come together to form a hollow structure known as a microtubule.

### Final Answer:
Microtubules are made of **tubulin**.

---