Microtubules are composed of protein subunits known as: Actin Keratin Tubulin Collagen

### C. Tubulin

## Step1: Identify the Composition of Microtubules### Microtubules are a component of the cytoskeleton in eukaryotic cells. They are cylindrical structures that are made up of protein subunits.## Step2: Recognize the Protein Subunit of Microtubules### The protein subunits that make up microtubules are known as tubulin. These subunits polymerize to form the microtubule structure.