Biochemistry Protein Structure and Function

Question 1

Which level of protein structure refers to the sequence of amino acids in a polypeptide chain?

Accepted Answer

Primary structure

Answer

Primary structure is the linear sequence of amino acids linked by peptide bonds, which ultimately determines all higher levels of protein structure.

Question 2

Alpha-helices and beta-pleated sheets are examples of which level of protein structure?

Accepted Answer

Secondary

Answer

Secondary structure describes local folding patterns stabilized by hydrogen bonds between backbone amide and carbonyl groups.

Question 3

Which bond is primarily responsible for maintaining the tertiary structure of a protein in an aqueous environment?

Accepted Answer

Hydrophobic interactions

Answer

Hydrophobic interactions drive the burial of nonpolar side chains in the protein core and are the dominant force in tertiary structure stabilization.

Question 4

Hemoglobin is an example of a protein with which level of structural organization?

Accepted Answer

Quaternary

Answer

Quaternary structure describes the assembly of two or more polypeptide subunits, as seen in hemoglobin's four globin chains.

Question 5

Which amino acid can form disulfide bonds that stabilize protein structure?

Accepted Answer

Cysteine

Answer

Cysteine residues contain thiol (-SH) groups that can be oxidized to form covalent disulfide (-S-S-) bonds between chains or within a single chain.

Biochemistry Practice Test