Florida Barber License Practice Test

Which cross bond is the strongest and can only be broken by a chemical solution?

1. Hydrogen bond

2. Salt bond

3. Disulfide bond

4. Peptide bond

The correct answer is: Disulfide bond

The disulfide bond is recognized as the strongest type of cross bond in hair and is crucial in the structure and stability of keratin proteins within hair and other proteins. These bonds are covalent links formed between the sulfur atoms of two cysteine amino acids. Due to their strong chemical nature, disulfide bonds provide significant strength and resilience, which are essential for maintaining the shape and integrity of hair. Breaking disulfide bonds requires specialized chemical solutions, such as those containing thioglycolic acid or other reducing agents, as these treatments can break the covalent bonds without damaging the overall structure of the hair if applied correctly. This characteristic makes disulfide bonds particularly important in processes like perming and relaxing treatments, where the structure of the hair is intentionally altered. In contrast, hydrogen bonds and salt bonds are relatively weaker and can be easily disrupted by physical means such as heat and water, thus being less significant in terms of strength. Peptide bonds, while also strong, primarily connect amino acids in the protein backbone rather than serving as structural cross-links in hair. Understanding the nature of disulfide bonds is crucial for anyone in the barbering or cosmetology field, as it directly impacts the techniques used in hair treatments and styling.