DR SHARMISTHA CHAKRAVARTY
DEPT OF ZOOLOGY
BARNAGAR COLLEGE SORBHOG
Based on:
Nutritional requirement
R group
Polarity
If the carbon is attached to four different
groups it is assymetric and therefore exibits
isomerism.
The amino acids except glycine possess four
distinct groups (R,H,COO-, NH3+) held by α
carbon.
Thus all the amino acids have optical isomers
except glycine.
Proteins are composed of L αamino acids
It is a secondary level of
protein organisation in
which backbone of the
peptide chain is extended
into zig zag arrangement
like a series of pleats.
The beta pleated sheet
can be formed between
two peptide chains or
between different
segment of same peptide
chain.
Amino acids like
tryptophan, tyrosine,
phenylalanine, isoleucine
adopt beta sheet
conformation