- No.3. What are polysaccharides? Give their properties.
Answer. Polysaccharides contain hundreds to thousands of monosaccharide. Examples of polysaccharides are starch and cellulose. They are amorphous solids. They are tasteless and insoluble in water. They are non reducing in nature. They are macromolecules.
Polysaccharides are starch and cellulose. Starch is found in cereal crops; wheat, barley, maize, rice, etc. Cotton is pure cellulose.
- No.4. Explain the sources and uses of proteins.
Answer. Proteins make up more than 50% of the dry weight of animals. Each protein and carries out a specific function. Sources and uses of protein are as follows
(i) Sources of animal’s proteins are meat, mutton, chicken, fish, eggs. These are used as food by human beings as they are essential for the formation of protoplasm.
(ii) Enzymes are proteins that are produced by the living cells. They catalyze the chemical reactions taking place in the bodies. They are highly specific and have extraordinary efficiency. Many enzymes are used as drugs. They control the bleeding and are used for the treatment of blood cancer.
(iii) Hides are proteins. These are used to make leather by tanning. Leather is used to make shoes, jackets, sports items, etc.
(iv). Proteins are found in bones. When bones are heated they give gelatin. Gelatin is used to make bakery items.
(v) Plants also synthesize proteins such as pulses, beans, etc. These are used as food.
- No.5. Explain amino acids are building blocks of proteins?
Answer. Two amino acids link through peptide linkage. Peptide linkage (bond) is formed by the elimination of water molecule between the amino group of one amino acid and carboxyl acid group of another, such as
H2N-CH-COOH + HNH-CH-COOH -H20 H2N – CH-C — NH- CH-COOH
R R R R
(Dehydration) Peptide linkage
When thousands of amino acids polymerize they form protein.
- No.6. Explain the sources and uses of lipids.
Answer. Fats and oils are high energy foods. They are source of vitamins A, D and E. They are used to build brain cells, nerve cells and cell membranes. They are insoluble in water but soluble in organic solvents. The fats stored in the body are poor conductor of heat and electricity. Fats and oils are synthesized naturally by animals, plants and marine organisms.
(i) Animal fats are found in adipose tissue cells. Animals secrete milk from which butter and ghee are obtained. Butter and ghee are used for cooking and frying of food, for preparing bakery products and sweets.
(ii) Animal fats are used in soap industry
(iii) Plants synthesize oils and store them in seeds. Examples are sunflower oil, coconut oil, groundnut oil and corn oil. These oils are used as vegetable oils or ghee for cooking and other purposes.
(iv). Marine animals like salmon and whales are also source of oils. These oils are used as medicines, e.g., cod liver oil.
- No.7. Give the importance of vitamins. Answer.
(i) Each vitamin plays an important role in the healthy development of our body.
(ii) Natural vitamins are organic food substances found only in plants and animals. Our body is unable to synthesize vitamins. Because of this, they must be supplied either directly in the diet or by way of dietary supplements. They are absolutely necessary for our normal growth.
(iii) Vitamins cannot be obtained without ingesting food. That is why it is suggested that vitamins must be taken with meal. They help to regulate our body’s metabolism.
- No 8. Describe the sources uses and deficiency symptoms of fat soluble vitamins.
|i||Vitamin A||Dairy products, eggs, oils and fats, fish It can also be obtained from the beta carotene found in green vegetables, carrots and liver||Maintains the health of the epithelium and acts on the retina’s dark adaptation mechanism.||Night blindness eye inflammation.
|ii||Vitamin D||Fish liver, dairy products, oils and fats. Vitamin D is formed in the skin when it is exposed to sunlight.
|Has a role in the absorption of calcium, which is essential for the maintenance of healthy bones.