Proteins, Uses, Types of Proteins, Importance, Classification, Protein Rich Foods



Protein rich food

Proteins are defined as the building blocks of life. Proteins are the most diverse class of biomolecules, both structurally and functionally, and have evolved to accomplish many tasks in living systems. The variety of structures and sizes is quite remarkable. Gro EL is a large, barrel shaped protein consisting of 14 subunits and an overall molecular weight of 840,000 that assists in protein refolding. Very small proteins, generally labelled antimicrobial peptides (AMPs), ranging from 15-50 amino acids function as part of the innate immunity in multicellular organisms

Table Of Content
  • What are Proteins
  • Importance of Proteins
  • Classification of Proteins
  • Foods containing Protein


Proteins may be defined as the high molecular weight mixed polymers of α-amino acids joined together with peptide linkage (-CO-NH-).
Proteins are the chief constituents of all living matter. They contain carbon, hydrogen, nitrogen and sulphur and some contain phosphorus also.

Importance of proteins
Proteins are the essence of life process.
  • They are the fundamental constituents of all protoplasm and are involved in the Structure of the living cell and in its functions.
  • Enzymes are made up of proteins
  • Many of the hormones are Proteins.
  • The cement substances and the reticulum,  which bind or holds the cells are tissue or organs are made up partly of proteins
  • They execute their activities in the transport of oxygen and carbon dioxide by haemoglobin and special enzymes in the red blood cells.
  • They function in the homeostatic control of the volume of the circulating blood, that of the intestinal fluids through the plasma proteins.
  • They are involved in blood clotting through thrombin, fibrinogen and other Proteins factors.
  • They act as the defence against infection by means of protein antibodies.
  • They perform hereditary transmission by nucleo proteins of the cell nucleus.

Classification of Proteins

Proteins are classified by their:
  •  Electrochemical indications (acidic, basic and neutral). Explain and give examples
  •  polarity ;polar (hydrophobic), nonpolar (hydrophilic), amphiphilic. Explain these terms.
  •  Function (transport, enzymes, hormones, antibodies etc)
  •  chemical composition(simple and complex)
  • Simple proteins(Describe the amino acid composition, the molecular mass, the charge , the structure and functions of the following:) Protamines -Albumin, Histones -Globulin

        Simple proteins

Class of Proteins








Soluble in water, coagulable by heat and

precipitated at high salt concentrations.


Serum albumin, egg albumin, lactal albumin

(Milk), leucosin (wheat), legumelin





Insoluble in water, soluble in dilute salt

solutions and precipitated by half saturated

salt solutions.


Serum globulin, vitellin (egg yolk), tuberin

(potato), myosinogen (muscle), legumin





Insoluble in water but soluble in dilute

acids and alkalis. Mostly found in plants.


Glutenin (wheat), oryzenin (rice).




Insoluble in water and absolute alcohol but

soluble in 70 to 80 per cent alcohol.


Gliadin (wheat), zein (maize).




Basic proteins of low molecular weight. Salmine (salmon sperm).

Soluble in water, dilute acids and alkalis.


Not coagulable by heat.




Soluble in water and insoluble in very

dilute ammonium hydroxide.


Globin of haemoglobin and thymus





Insoluble in water, dilute acids and alkalis

Keratin (hair, HOM, nail, hoof and feathers),

collagen (bone, skin), elastin (ligament). 

Conjugated Proteins

Class of Proteins





Composed of simple basic proteins

(protamines or histones) with nucleic

acids, found in nuclei. Soluble in water.


Nucleoprotamines and nucleohistones.


Combination of proteins with lipids, such as cholesterol and phospholipids etc.


Lipoproteins of egg-yolk, milk and  As fatty acids, membranes, lipoproteins of blood.




Combination of proteins with

carbohydrate (mucopolysaccharides).

Mucin (saliva), ovomucoid (egg white osseomucoid (bone), tendomucoid




Contain phosphorus radical as a prosthetic group


Caseinogen (milk), ovovitellin (egg yolk)



Contain metal ions as their prosthetic

groups. The metal ions generally are Fe,

Co, Mg, Mn, Zn, Cu etc.


Siderophilin (Fe), ceruloplasmin (Cu).



Contain porphyrin (with a metal Ion) as their prosthetic group


Haemoglobin,  myoglobin, glactase


Contain riboflavin as their prosthetic Flavoproteins of liver and kidney groups. 

Flavoproteins of liver and kidney

Complex Proteins

  • The chemical composition and structure of complex proteins.
  •  Protein component- Apoprotein
  •  Nonprotein component-Prosthetic group
  • Principle of classification (based on the name of the prosthetic group) and classes of complex proteins.

  • Dairy Products

  • Greek Yoghurt 
  • Cottage Cheese
  • Regular Yoghurt
  • Milk, Skim 
  • Soy milk 
  • Mozzarella 
  • String Cheese

  • Meat, Poultry, Eggs

  • Chicken, skinless
  • Steak 
  • Turkey, roasted.
  • Lamb
  • Pork 
  • Ham 
  • Egg, 

  • Seafood

  • Salmon 
  • Tuna
  •  Shrimp 
  • Lobster 
  • Scallops 

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