Which of the following best describes how a disulfide bond in human hair is formed ?
a. Oppositely charged atoms in the hair are attracted to one another to form weak physical cross - link side bonds
b. Amino acids are chemically bonded to each other , end to end , to form a polypeptide chain
c. Oppositely charged atoms are attracted to each other to form cross - linked side bonds between adjacent polypeptide chains
d. Sulfur atoms on neighboring cysteine amino acids within polypeptide chains in the hair join .