Final answer:
Keratin is a fibrous protein that makes up hair, nails, and skin. The individual units of keratin, called keratinocytes, are linked together through a process of bonding and coiling.
Step-by-step explanation:
Keratin is a fibrous protein that makes up hair, nails, and skin. The individual units of keratin, called keratinocytes, are linked together through a process of bonding and coiling. Three alpha-helices form a left-handed coil called a protofibril, and eleven protofibrils are bonded and coiled together to make a microfibril. Hundreds of these microfibrils are then cemented into an irregular bundle called a microfibril, creating a complete strand of hair.