Polypetides and proteins
L.O.:
• Explain the formation of a peptide (amide) linkage
between α-amino acids to form polypeptides and
proteins.
• Describe the acid and alkaline hydrolysis of proteins
and peptides to form α-amino acids or carboxylates.
Formation of a dipeptide between glycine and
alanine
Peptide: compound containing amino acids linked
by peptide bonds.
Peptide bond: amide bond in proteins and
peptides.
Formation of a dipeptide between glycine and
alanine
Draw an alternative dipeptide made from the
condensation of glycine and Alanine.
Alternative reaction of alanine and glycine
Section of a polypeptide showing four different
amino acids
Acid hydrolysis of a dipeptide
Reaction conditions: reflux with HCl for 24 hours.
Alkaline hydrolysis of a polypeptide chain
Reaction condition: NaOH, heat
Note: sodium salts are formed.
Peptide hydrolysis (powerPoint)
Draw the organic products formed when the
following protein is heated with concentrated
hydrochloric acid:
CH3
OH
O
HO
C
H
O
N
C
C
H
H
CH2
N
H
C
H
O
C
O
CH3
C
H
N
H
C
CH2
C
N
H
H
H