[Biology Form 4] Proteins

Proteins play an important role in the formation of cellular components, cells and tissues in the human body.

They are also needed for growth and development. Without them, we will not grow or be able to repair damaged tissues in our body.

Among the substances made up of proteins in the human body are haemoglobins, antibodies, enzymes, certain hormones, muscle tissues and part of the cell membrane.

• The basic building block of proteins is the amino acid.
  
  
• There are 20 types of amino acids.
  
  
• Of these, the essential amino acids are the ones that cannot be synthesised by the body and must be obtained from the food we eat.
  
  
• Five example of amino acids are leucine, tryptophan, glutamic acid, valine and serine.
  
  
• If amino acids are known as monomers, proteins are polymers.
  
  
• When two amino acids are joined together, a dipeptide is formed.
  
  
• The bond between two amino acids is called a peptide bond.
  
  
• The process in which polypeptides are formed from amino acids is known as condensation.
  
  
• Protein can be broken down to amino acids in a process called hydrolysis.
  
  
• A molecule that is a protein in nature can be used to speed up the process mentioned above. This molecule is an enzyme.

Resonance structures of the peptide bond that links
individual amino acids to form a protein polymer.

Chemical structure of the peptide bond

A peptide bond between leucine and threonine