Q43.Match List I with List II
List I
A. Glycine
B. Tyrosine
C. Tryptophan
D. Threonine
List II
I. Aromatic amino acid
II. Amino acid having chiral C-atom in side chain
III. Optically inactive
IV. Amino acid undergoes phosphorylation
Choose the correct answer from the options given below :
(1) A-IV, B-III, C-II, D-I
(2) A-III, B-II, C-IV, D-I
(3) A-III, B-I, C-IV, D-II
(4) A-III, B-IV, C-I, D-II
Correct Answer: (3) A-III, B-I, C-IV, D-II
Amino acids glycine, tyrosine, tryptophan, and threonine have unique structural and biochemical properties that match specific descriptions in List II.
Definitions
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Glycine (A): Simplest amino acid with H as side chain (-H), making its alpha carbon achiral and optically inactive (III).
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Tyrosine (B): Aromatic amino acid with phenol ring in side chain (I); also has -OH group that undergoes phosphorylation (IV).
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Tryptophan (C): Aromatic amino acid with indole ring (I); undergoes phosphorylation on nitrogen in some contexts.
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Threonine (D): Has chiral carbon in side chain (-CH(OH)CH₃), making both alpha and beta carbons chiral (II).
Option Analysis
Master glycine tyrosine tryptophan threonine amino acid matching for biochemistry exams. Correct option (3) pairs optically inactive glycine (III), aromatic tyrosine (I), phosphorylatable tryptophan (IV), and chiral-side-chain threonine (II).
Key Properties Explained
Glycine lacks side chain chirality, making it optically inactive (III)—unique among standard amino acids.
Tyrosine features aromatic phenol ring (I) and phosphorylatable -OH group.
Tryptophan is aromatic (indole ring) and undergoes kinase-mediated phosphorylation (IV).
Threonine has chiral β-carbon in side chain (II), creating two chiral centers.
Why Option 3 Wins
Perfect alignment: glycine’s H-side chain → achiral (III); tyrosine/tryptophan’s rings → aromatic (I/IV); threonine’s -CH(OH)CH₃ → chiral side chain (II). Others confuse aromaticity with phosphorylation.
Exam Memory Aid
“Glycine = No optics (III), Tyr/Trp = Rings + phosphate (I/IV), Thr = Two chirals (II).” Visualize structures: glycine flat, tyrosine phenolic, tryptophan bulky indole, threonine branched.
