Form 2 science

Chapter 2 (part 1)

Nutrition

2.1 Classes of Food

Why nutrition is important ?

• All living things need energy to continue their

life processes .

• This energy comes from the food we eat.

• Food is also needed for growing and repairing • Food is also needed for growing and repairing

worn-out body cells.

• Energy is released from food by the process of

respiration.

Food oxygen EnergyCarbon

dioxideWater

The food can be classified into seven

classes:

Carbohydrate Vitamins

Carbohydrate

• Sources:

Rice, potatoes, bread, flour

• Functions: • Functions:

To provide energy

Proteins

• Sources:

fish, eggs, milk, beans

• Functions:• Functions:

- For growth and the repair of worn- out cells.

- Prevent Kwashiorkor.

Fats

• Sources:

Cheese, butter, cooking oil, margarine

• Functions: • Functions:

To provide twice as much heat energy as

carbohydrates and to insulate the body

against heat loss.

Vitamins

• Sources:

Fruits, vegetables

• Functions:• Functions:

to maintain health and to prevent various

deficiency of disease.

Minerals

• Minerals are needed for normal growth and

development of the body. They are needed in

small quantities.small quantities.

• Sources:

For eggs, milk, fish

Fibre or roughage

• Sources:

Vegetables, fruits, cereals

• Functions:• Functions:

To prevent constipationconstipation and to help in

peristalsis. peristalsis.

Constipation =Constipation = sembelit 便秘便秘便秘便秘

Water

• Sources:

Water, fruits, beverages

• Functions:• Functions:

To maintain the liquid condition of the cells

and medium of various chemical reactions.

Facts About Vitamins

Water

soluble

•Vitamin B

•Vitamin C

Vitamins

Fat

soluble

•Vitamin A

•Vitamin D

•Vitamin E

•Vitamin K

Vitamins

• Functions:• Functions:

Promotes good night vision, maintains healthy

skin.

• Effect of deficiency:

Night blindness, dry scaly skin

• Functions:

Maintains healthy skin and nervous system.

• Effect of deficiency:

Beriberi, pellagra

Functions:• Functions:

Maintain healthy skin. It also promotes wound healing.

• Effect of deficiency:

Scurvy, difficulty in healing wounds.

Functions:• Functions:• Functions:

Helps the body absorb calcium and phosphorus.

• Effect of deficiency:

Rickets

• Functions:• Functions:

i) Helps in formation of red blood cells and

helps the body use vitamin K.

ii) Improve male fertility.

• Effect of deficiency:

Sterility Sterility = Kemandulan 不育症不育症不育症不育症

• Functions:

Promotes blood clotting

• Effect of deficiency:

Blood unable to clot.

Calcium

Sources:Sources:•• Sources:Sources:

Cheese, milk, eggs

•• Functions:Functions:

Calcium helps form and maintain healthy Calcium helps form and maintain healthy teeth and bones.

Helps blood clotting and construction of muscles.

•• Effects of deficiency:Effects of deficiency:

Rickets, osteoporosis

Sodium

• Sources:

Common salt, salted eggs, soy sauce…Common salt, salted eggs, soy sauce…

• Functions:

Regulate blood pressure , maintains the

function of muscles and nerves.

• Effects of deficiency:

Muscular cramps

Iron

• Sources:

Liver, eggs, spinach, lean red meat, salmon…Liver, eggs, spinach, lean red meat, salmon…

• Functions:

Formation of haemoglobin.

• Effects of deficiency:

Anaemia

Anaemia = anemia 贫血

Iodine

• Sources:• Sources:

seafood, leafy vegetables

• Functions:

Synthesis of thyroxine ( hormone that increases the rate of cell metabolism and regulates growth)

• Effects of deficiency:

Goitre

Phosphorus

Sources:• Sources:

Milk, cheese, eggs, meat, vegetable…

• Functions:

Formation of bones and teeth.

• Effects of deficiency

Rickets

Potassium

• Sources:

meat, nuts, bananas…

Functions:• Functions:

Maintain body fluid, proper function of nerves,

regulation of heartbeat.

• Effects of deficiency:

Weak muscles, paralysis

Paralysis is loss of muscle function for one or more muscles.

Food tests

1.Test For Starch

2.Test for Glucose

3.Test for protein3.Test for protein

4.Test for fats

Test for starch

(a) Add a few drops of iodine solution to a test

tube containing 3 ml of starch solution.

(b) The starch solution turns dark blue in colour.

Test for glucose

(a) Add about 1 ml of Benedict's solution Benedict's solution to a

test tube containing 3 ml of glucose solution.

(b) Heat the mixture in the test tube using a

water bath.water bath.

(c) A brick-red precipitate is formed.

Test for proteins

(a) Add a few drops of Millon's reagent to a test tube containing 3 ml of albumen solution.

(Albumen contains proteins)

(b) Heat the mixture in the test tube using a water bath.

(c) A red precipitate is formed.(c) A red precipitate is formed.

Test for fats

• Pour about 20 mm (depth) ethanol in to test

tube

• Add one drop of vegetable oil, and shake the

tube sideways until the oil dissolves in the tube sideways until the oil dissolves in the

alcohol.

• Add 2ml of water in the test tube.