أحمد محمود عيد 30104201601066

Kafrelsheikh University
Faculty of physical Therapy
The primary structure
It is the linear sequence of amino acid residues joined through peptide
bonds to form a polypeptide chain The peptide bonds are responsible for
the primary structure. It is a covalent bond
Each polypeptide chain starts on the left side by free amino group of the
first amino acid. It is termed N - terminal (or N - terminus) amino acid.
Each polypeptide chain ends on the right side by free carboxyl group of
the last amino acid termed C - terminal (or C - terminus) amino acid. The
remaining amino acids in the chains are termed: amino acids residues
(subunits) No other forces or bonds other than peptide bonds
Secondary structure
Secondary structure results from interaction of neighbor amino acid
residues (first and fourth) Hydrogen bonds are responsible for secondary
structure (in addition to the fracture of the peptide bond) It is the bond
between the hydrogen of -NH group of one amino acid residues and the
carbonyl oxygen (C =O) of other.
There are 2 main types of secondary structure of proteins:
A. ˈɑ - helix structure: It is rod - like structure with the peptide bonds
coiled tightly inside and the side chains of residues (R) extending
outward from the chain
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