The primary structure of a protein is the linear sequence of amino acids linked by peptide bonds.

Hydrogen bonds between the backbone NH and CO groups stabilize the secondary structure of a protein.

The alpha helix is the most common secondary structure in proteins, consisting of a regular, repeating pattern of hydrogen bonds between the backbone NH and CO groups.

Hydrophobic interactions between nonpolar side chains stabilize the tertiary structure of a protein by sequestering them away from the aqueous environment.

The quaternary structure of a protein refers to the three-dimensional arrangement of multiple protein subunits.

Myoglobin is an example of a globular protein, which has a compact, spherical shape.

Collagen is an example of a fibrous protein, which has a long, thread-like shape.

The primary function of enzymes is to catalyze chemical reactions, increasing their rate and specificity.

Amylase is an example of an enzyme, which catalyzes the breakdown of carbohydrates.

The term for the molecule that an enzyme acts upon is substrate.

The heme group is an example of a cofactor, which is a non-protein molecule that is required for the activity of an enzyme.

The term for the molecule that inhibits the activity of an enzyme is inhibitor.

Methotrexate is an example of a competitive inhibitor, which binds to the active site of an enzyme and prevents the substrate from binding.

Aspirin is an example of a non-competitive inhibitor, which binds to a site on an enzyme other than the active site and alters its conformation.

The term for the process by which cells regulate the expression of genes is gene regulation.