Chapter 4 - Protein Structure and Function

Front

What is the common structure of an amino acid?

Back

A central (α) carbon atom, an amino group (–NH₂), a carboxyl group (–COOH), a hydrogen atom, and a variable R group (side chain).

Front

What role does the R group play in amino acids?

Back

The R group determines the chemical nature of the amino acid (hydrophobic, polar, charged, etc.), how it interacts with other molecules, and its role in protein folding and function.

Front

What are the four side chain properties of amino acids?

Back

Nonpolar / Hydrophobic, Polar Uncharged, Acidic (Negatively Charged), Basic (Positively Charged).

Front

How are peptide bonds formed?

Back

Through a condensation reaction where the carboxyl group (–COOH) of one amino acid reacts with the amino group (–NH₂) of the next, releasing water (H₂O).

Front

What is the nature of a peptide bond?

Back

The peptide bond has partial double-bond character due to resonance, restricting rotation and making it planar.

Front

What is the protein backbone composed of?

Back

A repeating N–Cα–C sequence (nitrogen–alpha carbon–carbonyl carbon).

Front

What are the N-terminus and C-terminus of a protein?

Back

N-terminus: The end with a free amino group (–NH₂); C-terminus: The end with a free carboxyl group (–COOH).

Front

How are amino acids numbered in a polypeptide?

Back

From the N-terminus to the C-terminus.

Front

What allows protein folding despite the rigidity of peptide bonds?

Back

Rotation around the bonds around the α-carbon (N–Cα and Cα–C), though limited by steric clashes and chemical constraints.

Front

What is the difference between oligopeptides and polypeptides?

Back

Oligopeptides are short chains of fewer than ~20 amino acids; polypeptides are longer chains that may fold into complex 3D shapes.