Question

question 19 (1 point)
hair is approximately ___ percent protein.
70
a
b
90
c
30
d
50

question 20 (1 point)
which of the following is a situation in which a cosmetologist would allow the hair to cool before styling?
when salt side bonds are being formed by changes in ph during chemical servicing
a
b
when peptide bonds between amino acids are broken by a heat lamp during color processing
when disulfide bonds are converted to lanthionine bonds during servicing with a flat iron
c
d
when hydrogen side bonds have been broken by the heat from a curling iron

question 21 (1 point)
what are the major chemical elements that make up human hair?
hydrogen bonds, side bonds, and salt bonds
a
b
amino acids and polypeptide chains
carbon, oxygen, hydrogen, nitrogen, and sulfur
c
d
proteins, water, lipids, and traces of minerals

Explanation:

Question 19

Hair is composed mainly of a protein called keratin. In general, hair is approximately 90 percent protein.

Hydrogen bonds are weak physical bonds that can be broken by heat (like from a curling iron). When hydrogen side bonds have been broken by heat, allowing the hair to cool helps the hydrogen bonds re - form in the new style. Salt bonds are affected by pH changes, peptide bonds are strong chemical bonds not typically broken in normal styling (and if broken, it would damage the hair structure), and disulfide to lanthionine bond conversion is a more permanent chemical change (like in some chemical straightening, not related to cooling for styling).

The major chemical elements that make up human hair (keratin protein) are carbon (C), oxygen (O), hydrogen (H), nitrogen (N), and sulfur (S). Option a lists types of bonds, option b lists components of proteins (not elements), and option d lists larger - scale components (not elements).

Answer:

b. 90

Question 20