Question

Choose one of the following terms to match the description given. a. aldohexose n. glycogen b. saliva o. glycoside linkage c. antibody p. hormone d. cellulose q. hydrophobic e. \(\mathrm{CH}_{2} \mathrm{O}\) I. inhibition f. cysteine s. ketohexoses g. denaturation t. oxytocin h. disaccharides u. pleated sheet i. disulfide v. polypeptide j. DNA w. polysaccharides k. enzymes x. primary structure 1\. fibrous y. substrate m. globular z. sucrose amino acid responsible for permanent wave in hair

Short answer

The amino acid responsible for a permanent wave in hair is f. cysteine, as it forms disulfide bonds that contribute to the wavy or curly hair structure.

Step-by-step solution

Analyze given terms for their relevance to hair and amino acids

Check the terms in the list and eliminate the ones that are not directly related to amino acids or hair.

Identify the term associated with amino acid and hair structure

Remember that cysteine is an amino acid that plays a crucial role in the structure of proteins, such as keratin, which is a major component of hair. Cysteine contains a sulfhydryl group (-SH) that forms disulfide bonds (S-S) with other cysteine residues. These disulfide bonds provide strength and contribute to the wavy or curly structure of hair. Therefore, the correct answer is: f. cysteine

Key concepts

Amino Acids

Amino acids are the building blocks of proteins and play a crucial role in almost every biological process. There are 20 standard amino acids, each with a unique side chain that influences its chemical characteristics and function.

Amino acids share a common structure: they consist of a central carbon atom, an amino group ( ext{-NH}_2 ext{)}, a carboxyl group ( ext{-COOH} ext{)}, a hydrogen atom, and a unique R group, which varies for each amino acid. The properties of the R group determine the behavior of each amino acid, making them hydrophobic, hydrophilic, positively charged, or negatively charged.

Understanding amino acids is essential because their sequence dictates the protein structure, influencing how proteins interact and function in the body.

Disulfide Bonds

Disulfide bonds are covalent bonds that are vital in stabilizing the structure of many proteins. These bonds form when two cysteine molecules, a type of amino acid, come together through their sulfhydryl groups ( ext{-SH}). When two ext{-SH} groups react together, they form a disulfide linkage ( ext{-S-S} ext{)}.

Disulfide bonds serve several functions in proteins:

• They provide structural stability, maintaining the protein's shape.
• They are especially crucial in extracellular proteins, which face more variable environments.
• They help proteins withstand changes in temperature and pH.

For example, in hair, these bonds contribute to the physical properties of keratin, making hair either straight or curly depending on the pattern and abundance of disulfide linkages.

Protein Structure

Proteins are complex molecules with multiple levels of structure, each contributing uniquely to the protein's overall shape and function:

• Primary Structure: This is the sequence of amino acids in a polypeptide chain, connected by peptide bonds.
• Secondary Structure: Within this level, polypeptide chains form alpha helices or beta pleated sheets through hydrogen bonding.
• Tertiary Structure: This involves the three-dimensional folding of a protein, stabilized by various bonds, including disulfide bonds.
• Quaternary Structure: Involves the association of multiple polypeptide chains into a functional protein unit.

Each level of protein structure is critical to its overall function, and disruptions in any level can lead to loss of function or diseases. Disulfide bonds mainly influence the tertiary and quaternary structures, affecting the protein's stability and shape.

Keratin

Keratin is a structural protein found in hair, nails, and the outer layer of skin. It is known for its durability and resistance, largely attributed to the presence of disulfide bonds within its structure.

Keratin in hair is rich in cysteine residues, which form numerous disulfide bonds that cross-link the protein, conferring strength and flexibility. This cross-linking is responsible for the curls, waves, and overall texture of a person's hair.

• Within the keratin protein, disulfide bonds are crucial in maintaining hair's structure and integrity.
• Chemical treatments like perms and relaxers modify these bonds to change hair style and shape.

Understanding keratin and its role in hair can help in approaches to hair care, as maintaining these structures is key to healthy hair.