True about naturally occurring amino acids:
A. All are racemic mixturesB. Have specific genetic code
C. 20 in number
D. All are D-isomers
E. All are L-isomers
Ans. B. Have specific genetic code ;
• Of the over 300 naturally
occurring amino acids., 20 constitute the monomer units of proteins.
•
Both D-amino acids and non a anion acids occur in nature, but only L α — amino acids arepresent in proteins.
D-amino acids that occur naturally inclued D-serine and D-aspartate in brain
tissue, D-alanine and D-glutamate in cell walls of Gram +ve bacteria and
D-amino acids in some non-mammalian peptides and certain antibiotics.
• The genetic code is universal, specific, non-overlapping and degenerate. This universal nature of genetic code has lead to incorporation of 20 amino acids during protein synthesis in cells.
• Racemic mixture has both D and L isomers in equal concentration, thereby optically neutral.
• The genetic code is universal, specific, non-overlapping and degenerate. This universal nature of genetic code has lead to incorporation of 20 amino acids during protein synthesis in cells.
• Racemic mixture has both D and L isomers in equal concentration, thereby optically neutral.
