Texas Cosmetology Operator Written ExamChemistryHard
A cosmetologist is performing a permanent waving service. The perm solution breaks the disulfide bonds in the hair, and then the neutralizer reforms these bonds in a new shape. What type of bond is a disulfide bond, and how does its chemical nature contribute to the permanent change in hair shape?
- ADisulfide bond; it is a strong chemical bond that gives hair its strength and shape.
- BSalt bond; it is an ionic bond sensitive to pH changes.
- CHydrogen bond; it is a weak physical bond easily broken by water.
- DPeptide bond; it is the primary bond linking amino acids in the protein chain.
Show answer & explanationAnswer & explanation
Correct answer: A. Disulfide bond; it is a strong chemical bond that gives hair its strength and shape.
Disulfide bonds are strong chemical side bonds formed between two sulfur atoms in the keratin protein structure. They are responsible for a significant portion of hair's strength and elasticity. Breaking and reforming these bonds via chemical reduction (perm solution) and oxidation (neutralizer) allows for a permanent change in hair shape.
Why the other options are wrong
- B. Salt bonds are ionic side bonds, sensitive to pH, but not the primary target for permanent waving.
- C. Hydrogen bonds are indeed weak physical bonds, but disulfide bonds are not hydrogen bonds.
- D. Peptide bonds are the backbone of the protein chain, not the side bonds responsible for hair shape changes in perming.
Disulfide Bonds
Strong chemical side bonds in hair keratin, formed between two sulfur atoms, responsible for hair's strength and elasticity, and are broken and reformed during permanent waving and chemical relaxing.
- Strongest side bond
- Broken by reduction (perm solution)
- Reformed by oxidation (neutralizer)
- Contributes to hair's permanent shape
Memory trick: Disulfide's Strength Defines Hair's Length.