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PROTEINS

It has been taken from a Greek word proteous means primary or first ranking.

This term has been coined for the first time by a Dutch chemist G.J Molder in 1883.

DEFINITION

It the organic compound which is composed of amino acid and required for various functions such as catalytic, regulatory, and growth si known as protein.

The proteins are present more than 10000 per cell.

CHARACTERISTICS OF PROTEINS

·        They are the major structural component of cell protoplasm.

·        They are catalytic in nature such as enzymes.

·        Some are regulatory in function such as most hormones.

·        Some are called transport proteins.

In 1902 Emil Fischer, discovered that all the proteins are composed of chain of linear sequence of small units known as amino acids.

They are the building blocks of proteins.

DEFINITION

The organic compound which is composed of amino group and carboxylic group is known as amino acid.

There are twenty different types of amino acid are present in the living cells.

STRUCTURE

                                    H

                        H2N—C—COOH

                                     R

Where R group indicates an alkyl group or variable group.

CLASSIFICATION

A) ON THE BASIS OF SIDE CHAIN THERE ARE FIVE CLASSES.

1.  MONO-AMINO-MONO-CARBOXYLIC ACID AMINO ACID OR SIMPLE AMINO ACID OR AMINO ACID WITH   NON-POLAR ALIPHATIC SIDE CHAIN.

It contains six amino acid. NOTE. Formula to remember is (GAV-lips)

                                            i.            Glycine

                                          ii.            Alanine

                                        iii.            Valine

                                       iv.            Lucine

                                         v.            Iso-lucine

                                       vi.            Prolin

2.  MONO-AMINO-DI-CARBOXYLIC ACID AMINO ACID OR AMINO ACID WITH AROMATIC SIDE CHAIN.

         It contains three amino acids.

                                              i.            Tryptophane

                                            ii.            Tyrosine

                                          iii.            Phenylalanine.

3.  AMINO ACID WITH ACIDIC SIDE CHAIN.

                        It contains two amino acids.

                                                  i.            Glutamic acid

                                                ii.            Aspartic acid

4.  AMINO ACID WITH BASIC SIDE CHAIN.

        It contains three amino acids.

                                           i.            Lysine

                                         ii.            Arginine

                                       iii.            Histidine

5.  AMINO ACID WITH POLAR SIDE CHAIN.

It contain six amino acids. NOTE. Formula to remember is (TTP)

                                   i.            Asparagine

                                 ii.            Glutamine

                               iii.            Cysteine

                              iv.            Methionine

                                v.            Threonine

                              vi.            Serine

B). ON THE BASIS OF NUTRITIONAL VALUE.

          1. ESSENTIAL

           They are those proteins which we require or which our body cannot prepare.

           They are valine , methionine, iso-lucine, tryptophane, alanine, lucine and phenylalanine.

           2. NON ESSENTIAL.

               The remaining all are non essential or which our body can prepare.

FORMATION OF PROTEINS.

·        The amino acid contain both the basic or NH2 and acidic or carboxylic group.

·        The compound which contains both acidic and basic properties is known as amphoteric compounds.

·        Due to this amphoteric nature the amino acids unite with each other and form a long complex  chain of protein.

PEPTIDE BONDS.

The linkage between two amino acids through carboxylic group of one amino acid and amino group of another amino acid is known as peptide bond or peptide linkage.

Peptide bonds may be mono- peptide, di- peptide or poly- peptide