Methionine is sulphur containing AminoAcid

Enamel most likely effected by deficiency of vitamin A

Vitamin C deficiency is due to defect of Lysyl hydroxylase

Gout is a form of arthritis caused by the accumulation of uric acid crystals, specifically sodium urate crystals, in the joints. The body produces uric acid as a waste product during the metabolism of purines, which are substances found in certain foods and also synthesized by the body. High levels of uric acid can lead to the formation of these crystals, which cause inflammation and pain in the affected joints. Urea (Answer 1) is a waste product formed from the metabolism of proteins and amino acids, while guanine (Answer 3) and hypoxanthine (Answer 4) are purine bases involved in nucleotide metabolism, but they do not directly form the crystals seen in gout.

Vitamin D is crucial for the maintenance of bone health as it aids in the absorption of calcium from the digestive tract and facilitates the incorporation of calcium into bones. A deficiency in vitamin D can lead to osteoporosis, a condition characterized by weak and porous bones that are more susceptible to fractures, which is common in the elderly. While vitamin A (Answer 1) is important for vision and skin health, and niacin (Answer 2) and thiamine (Answer 3) have roles in energy metabolism and nerve function, respectively, vitamin D's primary role in calcium homeostasis makes it most relevant to bone loss in older individuals.