Describe the general structure of an amino acid and provide examples of amino acids with hydroxyl, sulfur-containing, aromatic, and basic side chains, including their structures.

Here are the answers to questions 4 and 5: 4. Amino acid classification and structures: The general structure of an amino acid is: c H \\ | \\ H_2N - |C - COOH \\ R where R represents the side chain. i. Amino acids with hydroxyl side chain: Serine (Ser, S): c H \\ | \\ H_2N - |C - COOH \\ CH_2OH Tyrosine (Tyr, Y): c H \\ | \\ H_2N - |C - COOH \\ CH_2-C_6H_4OH ii. Amino acids with sulfur-containing side chains: Methionine (Met, M): c H \\ | \\ H_2N - |C - COOH \\ CH_2CH_2SCH_3 iii. Aromatic amino acids: Tyrosine (Tyr, Y): (Structure shown above) iv. Basic amino acids: Lysine (Lys, K): c H \\ | \\ H_2N - |C - COOH \\ (CH_2)_4NH_2 v. Acidic amino acids: Aspartate (Asp, D): c H \\ | \\ H_2N - |C - COOH \\ CH_2COOH vi. Essential amino acids from the list: Valine* Leucine* Methionine* Lysine* 5. (a) i. Outline the characteristics of a peptide bond A peptide bond is an amide linkage formed by a dehydration reaction between the carboxyl group of one amino acid and the amino group of another amino acid. It exhibits partial double-bond character due to resonance between the carbonyl oxygen and the amide nitrogen, making it rigid and planar. This partial double-bond character restricts rotation around the C-N bond, but allows rotation around the N-C_ and C_-C bonds. The atoms involved in the peptide bond (C_-C(=O)-N(H)-C_) lie in a single plane. The peptide bond is uncharged, but the carbonyl oxygen can act as a hydrogen bond acceptor and the amide hydrogen as a hydrogen bond donor, which are crucial for protein secondary structures. 5. (a) ii. Define Isoelectric point (pI) The isoelectric point (pI) is the specific pH at which an amino acid, peptide, or protein has no net electrical charge. At this pH, the molecule exists predominantly as a zwitterion, meaning it has an equal number of positive and negative charges, and therefore, its overall charge is zero. At its pI, the molecule will not migrate in an electric field. Last free one today — make it count tomorrow, or type /upgrade for unlimited.