Amino Acids: Basics MCQs

keratan sulfates consist of repeating Gal-GlcNAc disaccharide units containing sulfate attached to the 6 position of GlcNAc or occasionally of Gal. Keratan sulfate I was originally isolated from the cornea, while keratan sulfate II came from cartilage. In the eye, they lie between collagen fibrils and play a critical role in corneal transparency. Changes in proteoglycan composition found in corneal scars disappear when the cornea heals. Reference: Harper's 32 nd edition, Page no. 637

Ans. is 'd' i.e., Fructose-6-phosphate [Ref Dinesh puri 3rdle p. 170] Amino sugars are dervatives of monosaccharides in which an amino group replaces the -OH residue on carbon-2 of hexose, such as glucose, galactose and mannose, The corresponding compounds are glucosamine, galactosamine and mannosamine, respectively. The amino acid group is usually acetylated, e.g. N- acetylglucosamine or N-actylgalactosamine. The amino sugars are required for the synthesis of glycolipids, glycoproteins and proteoglycans. They are synthesized from fructose-6-phosphate

Ans. is 'a' i.e.,Glutathione [Ref Harper 28thle p. 679-680] Angiotensin IIIHeptapeptide (6 amino acids) Angiotensin II Octapeptide (8 amino acids) Oxytocin Nonapeptide (9 amino acids) Bradykinin Nonapeptide (9 amino acids) Vasopressin Nonapeptide (9 amino acids) Glucagon Decapeptide (10 amino acids) Angiotensin I Decapeptide (10 amino acids)

Group of amino acid that contain only essential amino acid is branched chain amino acids (Leucine, Isoleucine, Valine) Group of amino acid that contain only nonessential amino acid is acidic amino acids, amide group containing amino acids, Imino acid, simple amino acids. Reference: Harper's 32nd edition, page 282

Valine is not an aromatic amino acid. Aromatic amino acids: Histidine (with imidazole ring) Phenylalanine (benzene ring) Tyrosine (phenol ring) Tryptophan (indole ring) Reference: Harper's Illustrated Biochemistry, 32nd Edition, Page Number-205.

Amino acid which can protonate and deprotonate means those which can act as a buffer . Amino acid whose pKa = pH of the medium has maximum buffering capacity . pKa of imidazole group of histidine is 6.5-7.4. At pH = 7, Imidazole group of histidine can act as buffer. Reference: Harper's 32nd edition, page 11,12

Aromatic amino acid with hydroxyl group- Tyrosine Nonaromatic amino acid with hydroxyl group - Serine and Threonine Reference: Harper's 32nd edition, page 17

Sulphur containing amino acids are Cysteine and Methionine . The Sulphur of Cysteine is provided by Methionine. Special group in Cysteine is Sulfhydryl group Thioalcohol (-SH) Special group in Methionine is Thioalcohol (C-S-C) Reference: Harper's 32nd edition, page 284