Proteins and Amino Acids

What are the major functions of proteins?

Enzymes, transport, structure, movement, communication, defense, and storage.

What are the building blocks of proteins?

Amino acids.

What four parts attach to an amino acid’s central carbon?

Amino group, carboxyl group, hydrogen, and side chain (R group).

How do you recognize an amino group?

–NH₂, often shown as –NH₃⁺ in water.

How do you recognize a carboxyl group?

–COOH, often shown as –COO⁻ in water.

What is the central or alpha carbon?

The carbon attached to the amino group, carboxyl group, hydrogen, and R group.

What determines an amino acid’s distinctive properties?

Its R group, which can be nonpolar, polar, or charged.

What is a peptide bond?

A covalent bond linking one amino acid’s carboxyl group to another’s amino group.

How is a polypeptide different from a protein?

A polypeptide is an amino acid chain; a protein consists of one or more chains arranged into a functional structure.

What is primary protein structure?

The sequence of amino acids, linked by peptide bonds.

What is secondary protein structure?

Local alpha helices and beta sheets, stabilized by hydrogen bonds between backbone groups.

What is tertiary protein structure?

The overall three-dimensional shape of one polypeptide, shaped by side-chain interactions.

What is quaternary protein structure?

Two or more polypeptide subunits assembled together.

What interactions help maintain tertiary structure?

Hydrogen bonds, ionic interactions, hydrophobic interactions, and disulfide bonds.

What is denaturation?

Loss of a protein’s normal shape, often causing loss of function; its amino acid sequence usually remains intact.