STPM Biology Biological Molecules Part 13 Amino Acids

1. Protein is an organic compound consisting of carbon, hydrogen, oxygen, nitrogen and sometimes sulphur and phosphorus.

2. Protein is a natural polymer, the monomer of protein is amino acid.

3. The basic structure of amino acid:

Basic structure of amino acid

4. Amino acid has a basic amino group, -NH2 and a acidic carboxyl group, -COOH and a side chain, R. There are 20 types of amino acids found in proteins. Different amino acids have different R chain.

Amino Acids	Three Letter Abbreviation
Alanine	Ala
Arginine	Arg
Asparagine	Asn
Aspartic acid	Asp
Cysteine	Cys
Glutamine	Gln
Glutamic acid	Glu
Glycine	Gly
Histidine	His
Isoleucine	Ile
Leucine	Leu
Lysine	Lys
Methionine	Met
Phenylalanine	Phe
Proline	Pro
Serine	Ser
Threonine	Thr
Tryptophan	Trp
Tyrosine	Tyr
Valine	Val

5. Amino acids can be classified into 4 major types based on the side chain (R).

• Non-polar amino acids
• Polar amino acids
• Basic amino acids
• Acidic amino acids

Non-polar amino acids

• Non-polar amino acids are amino acids with a non-polar side chain. 
• Examples: glycine, alanine, valine, leucine, methionine, isoleucine, phenylalanine, and tryptophan.

Non-polar amino acids

Polar amino acids

• Polar amino acids are amino acids with a polar side group.
• Examples: serine, threonine, asparagine, glutamine, tyrosine, and cysteine.

  

  Polar amino acids

Basic amino acids

• Basic amino acids have side chain which is an amino group, NH2, a base group. 
• Examples: lysine, arginine, and histidine.

Basic amino acids

Acidic amino acids

• Acidic amino acids have a side chain which is a carboxylic group, COOH.
• Examples: aspartic acid and glutamic acid.

Acidic amino acids