ProteinProteins are organic compounds containing carbon, hydrogen, oxygen and

nitrogen.

It may contain sulphur and phosphorous also.

Amino acid is the simplest unit of protein.

The quality of protein depends upon the amino acids they contain. There are

about 20 amino acids which are essential for human growth and development.

Human body cannot synthesize these amino acids. There fore, these amino

acids must be present in the proteins we eat.

Proteins are the most body building –materials.

They are essential for growth, repair and

replacement of injured parts.

Structure of protein

•A protein exhibits four levels of structural organization:

1.Primary Structure of Proteins: To define, primary structure of a

protein is the sequence of amino acids that are linked by covalent

peptide bonds to form a polypeptide chain. It is the description of

basic structure of a protein.

2.secondary Structure of Proteins: It is the repeated twisting and

folding of neighboring amino acids in the polypeptide chain The

secondary structure is stabilized by hydrogen bonds which form at

regular intervals along the polypeptide backbone.

3.TertiaryStructure of Proteins: The tertiary structure of a

protein refers to its three-dimensional shape of a polypeptide

chain. Each protein has a unique tertiary structure that

determines how it will function.

4.Quaternary Structure of Proteins:  When a protein

contains more than one polypeptide chain, the arrangement of

individual polypeptide chains relative to one another is

Quaternary structure.

Diagram of Protein structure

Sources of protein Good Sources Fair sources Poor sources

peas (200 g) 16.0g Brown rice (200g ) 4.4g 1 Carrot 0.4g

soya beans( 225 g) 11.5g Broccoli (100g ) 3.1g 1 Apple 0.3g

Cow's milk ½ pint 9.2g Porridge [water] (160g ) 2.4g Cream, double (20g ) 0.3g

Meat and fish 15-26 g -

Egg, boiled 7.5g Potatoes (200g ) 2.8g

Peanuts (30g ) 7.3g

Bread, (2 slices) 7.0g

Hard cheese (30g ) 6.8g

Functions of ProteinSome of the functions of proteins are given below.

1.Many proteins act as catalysts, thus enhancing the rate of

chemical reactions to such extents as needed by the living cells.

2.The fibrous proteins serve as components of the tissue holding

the skeletal elements together. 

3.Proteins are essential components of cytoplasm and therefore,

very essential for growth.

4.Proteins are essential for the repair of worn-out tissues.

5.In case of deficiency of carbohydrates and fats, proteins are

utilized for energy.

6.The muscles of body are formed from the proteins.

7. Protein acts as enzymes, co-enzymes and hormone and

control various body activities.

Protein Deficiency

Causes:

1.When the diet contains sufficient energy but not enough

protein.

2.Lack of sufficient energy in the diet.

In this situation the body’s own protein is used

as a source of energy.

Deficiency diseases

I.Kwashiorkor

In both types of protein deficiency kwashiorkor develops.

It is a disease of the child removed from the breast by the birth

of the next one, switching the child from a milk diet to a

starchy diet.

Signs and symptoms:

1.Pot belly(swollen stomach)

2.Thin legs

3.Ugly patches on skin

4.Mental retardation

5.Slow physical growth.

6.Reduced resistance to infection

II. Marasmus

• Due to a lack of energy in diet

Symptoms

1. Loose folds of skin

2. Very thin arms and legs

3. Slow growth of body

4. Child becomes lethargic

5. Very under weight.

Sources

•Retrieved on 6th of September, 2010 from

http://en.wikipedia.org/wiki/Protein_(nutrient)

•Retrieved on 6th of September, 2010 from

http://en.wikipedia.org/wiki/MarasmusNot to be confused

with Marasmius.

•Taylor,D.J., Green,N.P.O.,&Stout,G.W.(1997). Biological

science 1&2.United Kingdom: Cambridge University Press.