1. Chapter 2: Nutrition
2.1) Classes of Food
1. Importance of food
a) Provides energy to carry out living processes and functions
b) Provides energy to do work
c) Growth of new tissues and repair damaged tissues
d) Maintain good health and fight diseases
2. Food are divided into seven classes:
a)Carbohydrate e)Fibre / Roughage
b)Protein f)Minerals
c)Fat g)Water
d)Vitamin
3. Carbohydrate
a) Consists of carbon, hydrogen and oxygen
b) Includes sugar, starch, glycogen and cellulose
c) Smallest unit is glucose
d) Sources : wheat, bread, rice
e) Function : Provide energy
4. Protein
a) Consists of carbon, hydrogen, oxygen and nitrogen
b) Some may have sulphur and phosphorus
c) Smallest unit is amino acid
d) Sources : fish, meat, egg
e) Functions : (i) Growth and repair body tissues
(ii) Form enzymes, hormones and antibodies
(iii) Source of energy during starvation
(iv) Prevent kwashiokor
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2. 5. Fats
a) Consists of carbon, hydrogen and fat
b) Smallest unit are fatty acids and glycerol
c) Sources : butter, margarine, vegetable oil, fatty meat
d) Functions : (i) Source of energy (two times more than carbohydrate)
(ii) Heat insulator (keeps body warm)
(iii) Protect organs from injury
(iv) Dissolve fat-soluble vitamins (Vitamin A, D, E & K)
6. Vitamins
a) Organic compound needed in small amount.
b) Vitamin deficient can cause diseases but excess of vitamins can become toxins to our
body.
c) Divided into water soluble (Vitamin B & C ) and fat soluble (Vitamin A, D, E & K )
Vitamin Sources Effect of deficiency
A Carrots, tomatoes, egg, liver Night blindness (Xerophthalmia)
B Eggs, liver, vegetable, wheat Beri-beri, pellagra, nervous
disorder
C Orange, lemon Scurvy
D Eggs, milk, fish, liver, sun Rickets
E Leafy vegetable, wheat Anaemia
K Green leafy vegetable, liver, milk Blood clotting difficulty
7. Minerals
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3. a) Inorganic compounds required in small amount.
b) Needed for proper growth and development.
c) Excess minerals are excreted through sweat and urine.
Mineral Sources Functions Deficiency
Calcium Milk, egg, Form strong bones Osteoporosis
Phosphorus legumes, cheese and teeth Osteomalacia
Blood clotting Rickets
(calcium) Blood difficult to clot
(calcium)
Iodine Seafood, iodised Produce hormone for Goiter
salt metabolism
Growth and
development
Iron Liver, leafy Form haemoglobin Anaemia
vegetable, meat (red blood cell)
Transport oxygen
around our body
Sodium Table salt, fish, Nerve and muscle Muscle cramps
cheese functions Weak muscles
Maintain water Paralysis
balance
Potassium Grains, fruits
(banana),
vegetable
8. Fibre / Roughage
a) From cellulose in plants
b) Sources : leafy vegetable, brown rice, nuts and beans, fruits
c) Importance : Stimulate peristalsis
d) Lack of fibre causes constipation
9. Water
a) Average 8 glasses per day.
b) Lost a lot of water from sweat and urine
c) Sources : Drinks, fruits
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4. d) Importance : (i) Helps in digestion and excretion process
(ii) Controls body temperature
(iii) As medium for chemical reaction in body.
10. Food test
Food Test Procedure Observation
3
Starch Iodine Test 2cm starch solution + few Brown colour of iodine
drops iodine turns blue-black colour
Glucose Benedict 2cm3 glucose solution + Light blue colour of
Solution Test 2cm3 Benedict solution Benedict solution turns
Heat in water bath into red-brick precipitate
Protein Millon’s 2cm3 albumen + 2 drops White precipitate is
Reagent Test Million’s reagent formed when Millon’s
Heat in water bath reagent is added.
White precipitate turns
red-brick precipitate on
heating
Fat Emulsion Test Ethanol + 5 drops of Milky solution
cooking oil (emulsion) is formed
Shake and let it settle for 2
minutes
Spot Test 1 drop of cooking oil on Translucent spot is
filter paper formed
Allow to dry
2.2) Balanced Diet
1. Balanced diet is eating all classes of food in correct proportion.
2. Food pyramid
Fats, oils and sweets
Protein, dairy products
Fruits and vegetable
Carbohydrate
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5. 3. Factors determining balanced diet
Factor Example
People with larger size needs more food and nutrients than those
Size with smaller size
Male usually needs more food and nutrients than female
Gender
Those doing heavy jobs (construction, maid) needs more food and
Jobs nutrients than those doing light jobs (in the office)
Those in cold climate (North Pole) needs more fatty food
Climate compared to those in warm climate
People with health problem needs to take care of their diet
Health
Old people needs more calcium to strengthen their bones but
Age young people needs more carbohydrate and protein for growth
and development
4. Calorific value
a) Calorific value is of food is the amount of energy released from 1 gram of a particular
food
b) The energy stored in food is measured in calorie (cal) and Joule (J).
c) 1 cal = 4.2 Joule
d) Kamal has his lunch which consists of nasi lemak (421 cal), curry (530 cal), roti canai
(275 cal) and a cup of Milo (316 cal). Calculate the calorific value of the lunch Kamal
had in kiloJoule.
421 + 530 + 275 + 316 = 1542 cal
1542 cal X 4.2 J = 6476.4 J
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6. 2.3) Human Digestive System
1. The process of breaking down food into soluble and diffusible molecules.
2. Carried out by enzyme, a special protein produced by body to speed up chemical reactions
in body.
3. 3 main types of digestive enzymes:
a) Amylase (helps in carbohydrate digestion)
b) Protease (helps in protein digestion)
c) Lipase (helps in fat digestion)
4. Non-digestive enzymes that help in digestion:
a) Hydrochloric acid (produced in stomach )
b) Bile (produced in liver ) and stored in gall bladder
5. Human digestive system
Mouth
Oesophagus
Liver Stomach
Pancreas
Duodenum
Large intestine
Small intestine
Rectum
Anus
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7. 6. Digestion in human
Mouth (enzyme salivary amylase / ptyalin)
 Starch Maltose
Esophagus
 Food is churned into bolus via process
peristalsis
Stomach (gastric juice)
 Protease : Protein  Polypeptides
 Hydrochloric acid (not enzyme):
Stops action of enzyme from saliva and kills
bacteria
Partially digested food in stomach is known as
chyme
Duodenum (pancreatic juice + bile)
 Protease : Polypeptides  Peptides
 Amylase : Starch  Maltose
 Lipase : Fat  Fatty acids + glycerol
 Bile (not enzyme): Emulsify fat, neutralize
acid from stomach
Small intestine
 Maltose  Glucose
 Peptides  Amino acids
 Fat  Fatty acids + glycerol
2.4) Absorption of Digested Food
1. Digested food (glucose, amino acids, fatty acids and glycerol) and vitamins are absorbed
by villi of small intestine via diffusion into bloodstream.
2. Adaptations of small intestine
a) Has a lot of villi on its surface to increase the surface area
b) Each villus has thin epithelial wall to enable diffusion of digested food.
c) There is a rich network of blood capillaries in each villus.
d) Long (6m) for greater absorption.
e) Moist lining of epithelial wall allows digested food molecules to dissolve easily.
f) Peristalsis in small intestine enhances absorption
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8. 2.5) Reabsorption of Water and Defecation
1. Undigested food, minerals and water enters large intestine.
2. Most water and minerals are reabsorbed in the large intestine.
3. As water is absorbed, the mixture becomes solid waste, known as faeces.
4. Feaces is stored in rectum before being expelled via anus. This process is known as
defecation.
5. Lack of fibre will cause constipation.
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