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TYPES OF BIOMOLECULES

Depending upon the molecular weight and solubility, biomolecules are divided into two categories: Biomicromolecules and t biomacromolecules

I. Biomicromolecules

They are small sixed simple chemicals that have low molecular weight (less than 1000 Da), higher solubility and

simple conformation.

They are found in acid soluble pool.

It includes amino acids, sugars, nitrogen bases, lipids etc.

1. Amino acids • Amino acids are organic compounds, which are the building

blocks of proteins.

• As many as 300 amino acids occur in nature. Among these, only 20 amino acids are known as standard amino acids that commonly occur in proteins.

• Incorporation of protein, amino acids are controlled by triplet codes of DNA/mRNA.

• A protein may also possess non-coded amino acids. Such amino acids are called as rare amino acids. Rare amino acids are derived from the coded ones through modifications, E.g. Hydroxyproline from proline, hydroxylysine from lysine etc.

Structure and properties of amino acids: A typical amino acid is formed of an amino group (-NH₂).

an acid group (-COOH), -H and a variable group (R). The amino group (-NH₂) is basic and a carboxyl group (-COOH) is acidic in nature and are attached to the same carbon atom

(a-carbon).

Based on R group, there are 21 amino acids.

When R is H, Glycine. Glycine is the simplest amino

acid.

◆ When R is CH3, alanine. The chemical and physical properties of amino acids

upon the amino group, carboxyl group and R group. → More carboxyl group- acidic amino acid

depend

More amino group- basic amino acid ➤ Equal amino and carboxylic group- neutral amino acid. Amino acids are amphoteric compounds. They contain both

a basic group and an acidic group. Some amino acids have ionizable nature of -NH₂ and -COOH groups. Hence, in solutions of different pH, the structure of amino acids changes.

Isoelectric Point

Isoelectric point of the amino acid is defined as the point at which a molecule exists as zwitter ion with no net charge. Thus, at this point, the molecule is electrically neutral; it has maximum solubility, and least buffer capacity. All amino acids do not have the same isoelectric point (PI). The PI value of protein is determined by the nature of ionisable groups of amino acids. By taking the average pKa values of ionisable groups, PI can be calculated Depending on the structure and reaction, amino acids are divided

into seven types: