krishna-agrawala | Student

Human body needs certain chemicals derived from food for its effective working, growth and maintenance. These substances called nutrients fall into six broad categories.

  1. Water
  2. Carbohydrates
  3. fats
  4. Proteins
  5. Minerals
  6. Vitamins

Proteins meet the following needs of the body.

  1. Provide energy for working of the body
  2. Form an important material of which body parts are made. Muscles, skin, cartilages, and hair are mainly made up of proteins.
  3. Speed up chemical processes in the body. This is done through the action of a type of proteins called enzymes which are present in every cell.
  4. Another type of proteins called hormones regulate body processes and growth.
  5. Proteins in the form of antibodies fight diseases.

Proteins are large molecules that a are made up of smaller units called amino acids. Our body needs 20 different types of amino acids. Out of these total quantity of 11 amino acids are made within the body. Other 9 are either not made in the body or not made in sufficient quantities. Body gets its requirements of these 9 amino acids from food.

The best sources of proteins are milk, cheese, egg, lean meat and fish. These food items contain adequate amount of all the amino acids required by body. These proteins are called complete proteins. As opposed to these incomplete proteins contain only some of the required amino acids. It is possible to get the complete quota of all the required amino acids by using different incomplete proteins in combination. Major sources of incomplete proteins are cereals, legume, nuts, and vegetables.

giorgiana1976 | Student

Proteins are, from the chemical point of view, natural macromolecular compounds, with the structure of polypeptides, which form-amino acids by hydrolysis. They contain besides carbon, hydrogen, oxygen, nitrogen, sulfur, potassium, and other halogens. Some hormone containing proteins, they having the role of regulating the activity of the body. They patricipates at formation of antibody, helping to rid of toxins and microbes. Formation of enzymes and yeast requires presence of proteins. And last but not least, they participate in the formation of carbon dioxide, water, by the energy intake resulted from their combustion.
Daily diet contains a mixture of amino acids. From this mixture, most amino acids can be synthesized by the body, but 8 of them can be introduced into the body only through food. Through food,   into the body are introduced proteins that come from 2 sources: crop and animal.Those of animal origin (meat, milk, eggs), which are indispensable to a rational nutrition, have the advantage that are rich in protein, but the disadvantage that they are expensive, are made with a high consumption of plant products and are deficient in quantitatively terms .Those of vegetable origin (cereals, oilseeds and pulses), are the cheapest, so available, in the most large quantity, for the earth'  population.Some vegetable proteins can successfully replace animal protein, e.g. egg protein can be substituted for soy. Plant seed oil, also give high percentage of proteins: sunflower, groundnuts, cotton. Biological value  represents the  percentage of nitrogen kept by the body.It is determined by the presence or absence of certain amino acids in certain proportions, in the protein. After the biological value, we can classify the proteins in food:
-complete protein, containing all essential amino acids (lysine, methionine, isoleucine, tryptophan), needed to maintain protein balance of body  in optimal proportions for the synthesis of body protein balance. In the normal quantity, they maintain growth. Eg milk, cheese, eggs, meat . -partially

- complex protein, which also contain all the essential amino acids (lysine, methionine, isoleucine, tryptophan), but not in optimal scale for synthesis of body protein balance. To maintain body growth, we need a double intake of complete protein. Ex: wheat, rice, oats, some dried legumes.

ruby01 | Student



Procurement of substances for the growth of the body, repair of the worn out tissues and to obtain energy to do work. The chemical substances present in the food. They provide the metabolic energy and the raw materials for growth, repair of tissues, production of gametes and protection from diseases. A nutrient made up of essential and nonessential amino acids, human body manufactures 13 nonessential amino acids, which aren't available from food. y sources.


Organism makes its own food[ organic compounds] from simple [inorganic] raw material i.e. phytoplankton, alga, plants and some bacteria.

Heterotrophic nutrition

[Gk trophe food] Incapable of manufacturing organic compounds from inorganic raw materials, therefore requiring organic nutrients from the environment. OMode of Heterotrophic nutrition: it depends upon type and availability of food. Based on the methods of procurement or collection of food, heterotrophic nutrition is classed into four major types of nutrition. These are :saprotrophic[saprophytic/saprozoic], parasitic holozoic, and symbiotic.

Saprophytic Nutrition:

Taking dead decay organic matter in form of food by plant like organisms[with cell wall] e.g. Fungi [yeast, moulds and mushrooms] and bacteria.

saprozoic nutrition

Taking dead decay organic matter in form of food by animal like organisms[without cell wall] . A few animals (e.g. spiders, house-fly, etc.) do not ingest solid food.

Parasitic Nutrition

Live on or inside other organisms and derive their food from them but do not kill them.

symbiotic nutrition or mutualism.

Type of nutrition in which two organisms or animals might live in association and derive nutrition from each other. This is the case with some symbionts For example, Escherichia coli that lives in the intestine of man synthesises vitamin B12, which is used by man and the E. coli receives, in return, simpler food from the intestine of man.

Proteins are considered either complete proteins (which supply enough essential amino acids) or incomplete proteins (which lack adequate essential amino acids).


Examville Tutor


sandali | Student

Protein are made up of long chains of amino acids. It contains the elements carbon, hydrogen, oxygen, nitrogen and usually sulphur. Examples of foods containing proteins are lean meat, eggs, beans, fish, milk and milk products such as cheese. Proteins (during digestion) is digested to amino acids and is absorbed into the blood stream & eventually reach the cells of the body. There, the amino acids are assembled to form proteins of the protoplasm (nucleus, cytoplasm and cell membrane) and its constituent enzymes. Plants can build up amino acids that they need from carbohydrates, which they make;anyway animals cant do this. Proteins are very important during pregnancy period and growth. Growing children also need an adequate supply of protein and the lack of protein in the diet may cause the deadly disease, kwashiorkor in small children. So, protein is very important to our diets!!! Anyway if proteins are eaten in excess, there will be more amino acids in the body than needed and so are converted into carbohydrates, as they reach the liver. Amino acids cannot be stored!!!

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