Basic Biology

Biological Compounds

What are proteins and what is their purpose?

Proteins are large, complex molecules composed of smaller structural subunits called amino acids. All proteins contain carbon, hydrogen, oxygen, and nitrogen, and sometimes sulfur, phosphorus, and iron. Human life could not exist without proteins. The enzymes that are required for all metabolic reactions are proteins. Proteins also are important to structures like muscles, and they act as both transporters and signal receptors.

Type of Protein Examples of Functions
Defensive Antibodies that respond to invasion
Enzymatic Increase the rate of reactions; build and breakdown molecules
Hormonal Insulin and glucagon, which control blood sugar
Receptor Cell surface molecules that cause cells to respond to signals
Storage Store amino acids for use in metabolic processes
Structural Major components of muscles, skin, hair
Transport Hemoglobin carries oxygen from lungs to cells


This is a web preview of the "The Handy Anatomy Answer Book" app. Many features only work on your mobile device. If you like what you see, we hope you will consider buying. Get the App