Alanine is a nonpolar amino acid due to its side chain being a methyl group, which is hydrophobic.

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

Hydrogen bonds between the backbone atoms of amino acids are responsible for maintaining the secondary structure of a protein, such as alpha helices and beta sheets.

The tertiary structure of a protein is the three-dimensional arrangement of amino acids in space, including the folding of the polypeptide chain.

Myoglobin is a globular protein with a compact, spherical shape, while collagen, keratin, and actin are fibrous proteins with elongated structures.

The quaternary structure of a protein is the arrangement of multiple polypeptide chains into a single functional unit.

Hemoglobin is a protein with a quaternary structure, consisting of four polypeptide chains.

The structure of a protein is determined by the sequence of amino acids, the interactions between amino acids and other molecules, and the environment in which the protein is located.

The function of a protein is determined by its structure, its interactions with other molecules, and the environment in which it is located.

Pepsin is a protein that functions as an enzyme, specifically a protease that breaks down proteins into smaller peptides.

Insulin is a protein that functions as a hormone, specifically regulating blood sugar levels.

Collagen is a protein that functions as a structural protein, providing strength and support to tissues.

Sodium-potassium pump is a protein that functions as a transport protein, moving sodium and potassium ions across cell membranes.

Antibodies are proteins that function as immune proteins, recognizing and binding to specific antigens.

Ferritin is a protein that functions as a storage protein, storing iron in cells.