BIOLOGY [3 marks Question Answer]

Digestion is the process of breaking down complex food materials into simpler substances by the action of enzymes.
Need for a digestive system:
(i) Large complex molecules like carbohydrates, proteins and lipids need to be broken down to simpler molecules. These simpler molecules can then be absorbed and utilized by the body.
(ii) The breaking down of complex food molecules into their simpler form is possible only through the process of digestion.
(iii) During digestion, large complex macromolecules present in food are converted into small simpler molecules, which can be simplified in different compartments of digestive system only.

Test for starch:

1. Take the food item to be tested. Put it into a test-tube containing water and boil to make a solution.
2. Cool the solution and add 2-3 drops of dilute iodine solution to it.
3. Blue-black colour of the solution indicates the presence of starch in the food item.

Test for proteins:

1. Take the food item to be tested in a test tube.
2. Add few drops of dilute nitric acid to it.
3. Heat the test-tube gently.
4. Rinse off the acid with water and add few drops of ammonium hydroxide to it.
5. Colour change from colourless to yellow and then from yellow to orange red indicates the presence of protein in the food item.

Importance of water in our body:

1. Water is the major component of blood, which carries nutrients and oxygen, to and from all the cells.
2. It is the major component of saliva and mucous, which lubricate the membranes that line our digestive system beginning with the mouth.
3. It helps in regulating the temperature of the body.
4. Water is very essential for digestion as well as absorption of food.

The liver is an important organ in our body as it serves the following functions:

• Production of bile
• Control of blood sugar levels
• Control of amino acid levels
• Synthesis of foetal red blood cells
• Produce fibrinogen and heparin
• Regulate blood volume
• Destroy dead red blood cells
• Store vitamin and minerals
• Excrete toxic and metallic poisons
• Produce heat
• Detoxification

Vegetarian menu for dinner:

Foodstuffs	Weight (gm/ml)
Cereals	320
Pulses	70
Green leafy vegetables	100
Root vegetables	75
Fruits	75
Milk	600
Fat and oil	30
Brown sugar and jaggery	30