AP Bio Study Guide

Big Idea 4.A

What is the structure and function of proteins?

Proteins are macromolecules that carry out many functions in the body including:

  • Growth and repair
  • Signaling between cells
  • Regulation (ex: hormones)
  • Enzymatic activity (catalyzing chemical reactions)
  • Movement (ex: action and myosin are protein fibers responsible for muscle contractions)

Proteins are polymers or polypeptides consisting of units called amino acids, which are joined by peptide bonds.

Each amino acid consists of a carboxyl group, an amine group, and a variable (R) all attached to a central carbon atom. The R group, also called the side chain or variable, varies between amino acids. The R groups are categorized by their chemical properties: hydrophobic, hydrophilic, acidic, or basic. The interactions among R groups ultimately determine the overall structure and function of a protein.