Oregon Cosmetology State Board – Hair Practice Test

Thio bonds, also known as disulfide bonds, play a crucial role in the structure and strength of hair. They occur between the sulfur atoms in the amino acids cysteine, which are abundant in keratin proteins. This relationship is fundamental since keratin is the primary structural protein found in hair, making it the correct context for the occurrence of thio bonds.

Keratin proteins are composed of long chains of amino acids, and the presence of disulfide bonds between these chains contributes significantly to the hair's elasticity and resilience. When these bonds are broken and subsequently reformed, it allows for chemical processes like perming and relaxing to alter the shape and texture of the hair.

While color pigments are important for hair color, they do not involve thio bonds. Water molecules, while vital for hair hydration, also do not form disulfide links. The amino acids themselves are the building blocks of keratin but do not inherently contain the structural bonds unless they are part of a keratin chain. Therefore, understanding the association of thio bonds with keratin proteins is key to grasping hair structure and chemistry.