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PinkMonkey Online Study Guide-Biology

16.1 Nutritional requirements, imbalances and deficiency diseases

Constituents of Food

The chief constituents of food are : (a) carbohydrates, (b) proteins, (c) fats and oils, (d) vitamins, (e) minerals, (f) water, and (g) roughage.

a) Carbohydrates : These organic compounds are intimately involved in life processes. They contain atoms C, H and O, the last two in the ratio 2:1. The general atomic composition is stoichiometrically represented as C (H2O). The simple sugars are the building blocks of carbohydrates. One gram of carbohydrate provides about 4 Kcal of energy.

There are three types of carbohydrates :

(i) Monosaccharides : simple sugars like glucose and fructose.

(ii) Disaccharides : double sugars like maltose, sucrose, etc..

(iii) Polysaccharides : complex sugars like starch, and glycogen.


Importance of carbohydrates in metabolism: Carbohydrates like glucose form respiratory substrate or fuel substances to produce energy. The excess of glucose is stored in the liver and muscles (glycogen) in animals and in the form of starch in plants. They are thus storage compounds in plants and animals respectively. Cellulose and chitin are carbohydrates which form structural materials for cell walls in plants and exoskeletons in animals like arthropods.

Bread, potato, sugarcane, plantains, grapes and cereals like wheat and corn are dietary sources of carbohydrates.

b) Proteins : These are the molecules which are the fundamental compounds of protoplasm that are indispensable for all life processes. Proteins contain "N" in addition to C, H and O and may also contain phosphorus and sulphur. These are the polymers of unit structures called amino acids. A molecule of protein yields about 4 Kcal. of energy.

Meat, fish, eggs, peas, beans and milk contain large amount of proteins.

Figure 16.3 Constituents of food

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Table of Contents

16.0 - Introduction
16.1 - Nutritional Requirements, Imbalances and Deficiency Diseases
16.2 - Organs of Digestion and Physiology of Digestion

Chapter 17





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