Similarities
Both polypeptide and polysaccharide are macromolecules and their polymers are built up from monomer.
They are organic
compounds in common.
The monomer of
polysaccharide is monosaccharide which is made up of carbon, hydrogen and
oxygen, ratio of hydrogen: oxygen= 2:1 while the monomer of protein is amino
acid which is made up of carbon, hydrogen, oxygen, nitrogen with sulphur, no
particular ratio.
They are formed by removal of water which is called condensation. And they can be broken down into subunits by hydrolysis.
Both polypeptide
and polysaccharide can act as an energy source for organisms, though
polypeptide is the last resort of energy source.
Each monomer of
carbohydrate is a ring structure and has
Adjacent
monosaccharide are joined by glycosidic bond between OH- groups of
two monomers while adjacent amino acids is linked together by forming the
peptide bond i.e. –C-C-N-C-C-N, with the R groups forming the side chain.
There are 20
essential amino acids due to different R groups. The R groups affect the
charge/ polarity and hydrophobicity of the protein molecules. No such feature
in carbohydrates.
Primary structure
of protein is due to different sequence of 20 different amino acids which give
rise to different proteins, there is no fix ratio of any
amino acids in a protein molecule. The secondary structure of protein is an α helix. The polymers of carbohydrates also coil up in
helix but may have branching chains. The tertiary structure of protein is a
3-dimensional shape molecule while there is no such tertiary structure in
carbohydrates.
There are two
types of polysaccharides: storage polysaccharides and structural
polysaccharides. Polypeptide can only be structural but not storage since it
will be broken down in a process called deamination.
Polypeptide can
act as enzyme to catalyst specific reaction. It will work best in optimum
temperature and pH. Also it will be denatured in extreme environment. However,
polysaccharides can’t act as enzymes.
Polysaccharides
are insoluble in water. Polypeptide will form a colloidal suspension when added
into water.