Hemoglobin contains four polypeptide chains per molecule. As individual items, and with no other information, the best evidence for this conclusion is
A) hemoglobin contains four iron atoms per molecule.
B) a molecule of hemoglobin binds four atoms of oxygen.
C) hemoglobin crystallizes in the cubic crystal form.
D) the molecular weight of hemoglobin is 64,000.
E) there are four N-terminal valine residues per molecule of hemoglobin.

Question

Quizplus · Accepted Answer

Each polypeptide chain in a protein has one N-terminal end, which is the start of the amino acid chain. Finding four N-terminal valine residues in hemoglobin strongly suggests there are four separate polypeptide chains, each beginning with valine.

Hemoglobin Contains Four Polypeptide Chains Per Molecule