Proteins

 Proteins are probably the most complex materials produced in nature. The name protein in derived from the Greek word proteins, meaning 'of prime importance'. The name is well  chosen because proteins are the basic of protoplasm and are present in all living organisms. Without proteins life would not be possible. Proteins are present in muscle, skin, hair and other tissue that make up the bulk of the body's nonbony structure. As enzymes they Catalyse bioche - mical reaction; as harmones they regulate metabony process; and as antibodies they resist and nullify the of toxic substances.

Plants syntheseies proteins from carbon dioxide, water, nitrates, sulhates, and phosphatic. Animal cannot synthesise proteins from these inorganic materials. Animals obtain proteins by eating plants or other animals, which in turn have obtained proteins from plants.

All proteins contain the elements carbon, hydrogen, oxygen, nitrogen, and sulphur. They may contain phosphorus, and traces of other elements like iron, copper, iodine, manhanese, and zinc. Most proteins do not show variation in their elementary composition. The average content of five main elements is given in show:

• Carbon
• Hydrogen
• Oxygen
• Nitrogen
• Sulphur

Proteins have very high molecular weight. Their molecular weight may range from 10,000 over 50 million. All proteins yeild amono acids upon complete hydrolysis. Thus proteins may be defined as the high molecular weight organic material which, upon complete hydrolysis, yields amino acids.

Classification

There are two methods for classifying proteins. One method classifies them according to composition as either simple proteins or conjugate proteins. The second method classified them according to their physiological functions.

• Classification According to Composition

(A) Simple Proteins, Simple Proteins are those which yields only a amino acid upon hydrolysis. They are furt subdivided according to their solubility in various solvents and also whether they are coagulated by heat.

(1) Albumins, Albumins are water- soluble proteins, which are coagulated by heat. They are found in plants and animals Examples are egg- Albumins and serum- Albumin.

(2) Globulins, Globulins are insoluble in water but soluble in dilute salt 🧂 sulution, which are coagulated by heat. They. are found in plants and animals. Examples are serum- Globulin and vegetable- Globulins.

(3), Scleroproteins, Scleroproteins are insoluble in water and most other solvent. They are found only in animals. Examples is keratin in hair and fingernails.

(4), Glutenins, Glutenins are insoluble in water but soluble in dilute ammonium hydroxide, which are not coagulated by heat. They are found in animals. Example is glutenin from wheat.

(5) Histones, Histones are soluble in water but insoluble in dilute ammonium hydroxide, which are not coagulated by heat. They are found in animals. Examples is globin in haemoglobin.

(6) Prolamines, Prolamines are insoluble in water but soluble in 70 per cent ethanol, which are not coagulated by heat. Examples are zein from corn and gliadin in haemoglobin.

(7) Protamines, Prolamines are soluble in water and dilute ammonium hydroxide, which are not coagulated by heat. Examples are salmins from salmon and sturine from structure.