protein
TRANSCRIPT
FISH
MILK
MEAT
EGG
PROTEIN
About two-thirds of the total dry mass of a cell is composed of proteins
ELEMENT IN PROTEIN
CARBONHYDROGEN
OXYGEN
NITROGEN
Amino acids are the subunits of all proteins
There are 20 biological important amino acids
Each amino acid carries two functional group :
• A carboxyl group ( - COOH) which is acidic
• An amino group ( -NH2) which is basic
Two amino acids can combine to form a dipeptide by a condensation reaction
between the carboxyl group of one and the amino group of the other
The resulting a bond liking the two amino acids that is called peptide bond
Long chains of amino acids are called polypeptides
• The peptide bond can be broken by hydrolysis with heat, dilute acids or by enzymes
• The loss of the three dimensional structure of a protein molecule is known as denaturation
The linear sequence of amino acids in a
protein molecule. The first proteins to have its sequence of amino
acids determined was the hormone insulin
Peptide chain becomes folded or twisted forming a helix or pleated sheet. The structure is maintained by
hydrogen bonding.
Bending and twisting of the polypeptides helix into a
compact structure.
Structured is maintained by ionic, disulphide and
hydrogen bonding
Myoglobin, a protein found in muscles, has the tertiary structure.
Enzymes antibodies and many hormones have this structure
as well
Different polypeptide chains combine with associated non-protein groups forming a large complex protein molecule. Haemoglobin, an oxygen binding protein,
has a quartenary structure
Human can synthesis 11 of the 20 different amino acids used in
protein synthesis. These amino acids are known as non essential amino acids
Examples of non essential amino acids are proline, glycine, and
glutamic acids
The remaining nine amino acids cannot be synthesised in human. The must be
included in the diet. They are known as essential amino acids
Examples of essential amino acids are lysine, valine, leucine and tryptophan