Download - 45820593 form-2-science-chapter-2-part-1 (1)
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Form 2 science
Chapter 2 (part 1)
Nutrition
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2.1 Classes of Food
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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
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The food can be classified into seven
classes:
Carbohydrate Vitamins
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Carbohydrate
• Sources:
Rice, potatoes, bread, flour
• Functions: • Functions:
To provide energy
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Proteins
• Sources:
fish, eggs, milk, beans
• Functions:• Functions:
- For growth and the repair of worn- out cells.
- Prevent Kwashiorkor.
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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.
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Vitamins
• Sources:
Fruits, vegetables
• Functions:• Functions:
to maintain health and to prevent various
deficiency of disease.
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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
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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
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Water
• Sources:
Water, fruits, beverages
• Functions:• Functions:
To maintain the liquid condition of the cells
and medium of various chemical reactions.
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Facts About Vitamins
Water
soluble
•Vitamin B
•Vitamin C
Vitamins
Fat
soluble
•Vitamin A
•Vitamin D
•Vitamin E
•Vitamin K
Vitamins
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• Functions:• Functions:
Promotes good night vision, maintains healthy
skin.
• Effect of deficiency:
Night blindness, dry scaly skin
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• Functions:
Maintains healthy skin and nervous system.
• Effect of deficiency:
Beriberi, pellagra
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Functions:• Functions:
Maintain healthy skin. It also promotes wound healing.
• Effect of deficiency:
Scurvy, difficulty in healing wounds.
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Functions:• Functions:• Functions:
Helps the body absorb calcium and phosphorus.
• Effect of deficiency:
Rickets
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• 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
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• Functions:
Promotes blood clotting
• Effect of deficiency:
Blood unable to clot.
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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
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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
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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
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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
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Phosphorus
Sources:• Sources:
Milk, cheese, eggs, meat, vegetable…
• Functions:
Formation of bones and teeth.
• Effects of deficiency
Rickets
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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.
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Food tests
1.Test For Starch
2.Test for Glucose
3.Test for protein3.Test for protein
4.Test for fats
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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.
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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.
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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.
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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.