Olfactory cells play an important role in allowing us to sense smells.

Olfactory cells play a role in sensing smells in the nose.

Macrophages play a role in taking in and breaking down foreign substances in the body.

Oocytes play an important role in the reproduction of organisms.

Multicellular organisms, unlike unicellular organisms, have specialized cells in their bodies that perform functions.

This reaction occurs through a chemical process.

He is an excellent chemist who made many discoveries.

He is an expert in petrochemistry.

It's difficult to decipher this chemical equation.

Understanding chemical equations is difficult.