1. A balanced diet containing the seven classes of food is necessary to meet daily nutritional requirements and prevent deficiency diseases. 2. The digestive system breaks down food through physical and chemical digestion in the mouth, stomach, and small intestine to absorb nutrients in the bloodstream. 3. Constipation can be caused by not eating enough fibre or drinking enough water, and can be cured by consuming laxatives, high-fibre foods, and more fluids.

1. Chapter 2 :
Nutrition
Classes Of Foods

2. 1. Food can be classified into seven main classes.
a. Carbohydrate
b. Protien
c. Fat
d. Vitamin
e. Mineral salts
f. Fibre
g. Water

3. a. Contain carbon,
hydrogen, and
oxygen.
b.Supply most of
the energy our
body needs.
c. Examples:
sugar, starch,
cellulose,
glycogen.

4. a.Contain carbon,
hydrogen, oxygen,
and nitrogen.
b. Needed for growth
and repair of body
tissues.
c. Examples: fish,
meat, egg

5. a.Contain
carbon,
hydrogen, and
oxygen.
b.Help to keep
us warm and
protect internal
organs.
c.Examples:
animal fats,
vegetable oils

6. a. Organic compounds
needed in small
amounts by our
body.
b. Needed for health
and growth.

7. Vitamin Source Function Deficiency
disease
A Carrot,liver, Fornightvision Nightblindness
fishliveroil, Healthyskin Skininfections
andgreen
vegetables
B Eggs,milk, Releasesenergy Beriberi
meat,yeast, from Anaemia
andcereals carbohydrates
Healthynervous
system
Healthyskin
Formationofred
bloodcells
C Freshfruitsand Healingof Scurvy(bleeding
vegetables wounds gums)
Resistanceto
diseases

8. Vitamin Source Function Deficiency
disease
D Madebyour Strongbones Rickets(soft
bodyin andteeth bonesanddental
sunlight,also decay)
foundinmilk,
eggs,fishliver
oil
E Vegetableoil, Maybeneeded  Sterility
wholegrains, forreproduction
nuts, Helpstofight
wheatgerm againstdiseases
K Madeinthe  Clottingofblood Prolonged
human bleeding
intestines,also
foundinegg
yolk,green
vegetables

9. a.Inorganic
compounds
needed by our
body,
b.Needed for
healthy growth
and development.

10. Mineral Source Function Deficiency
disease
Calcium Cheese,
milk,eggs, Strongbonesand Rickets
green teeth Osteoporosis
Bloodclotting Prolonged
vegetables
Muscleandnerve bleeding
activities Muscularcramps
Sodium Tablesalt, Maintainsbody  Muscularcramps
cheese, fluid
meat Proper
functioningof
nerves
Iron Meat,eggs, Neededtoform  Anaemia
green haemoglobininred
vegetables bloodcells
Iodine Seafood, Neededtomake Goitre(swellingof
iodisedsalt harmonesofthe thethyroidglandin
thyroidgland theneck)

11. Mineral Source Function Deficiencydisease
Phosphorus Eggs,meat, Rickets
milk,cheese, Strong Weakness
vegetables bonesand
teeth
Muscle
contraction
Stores
energy
Potassium Meat,nuts, Weakmuscles
bananas Maintains Paralysis
bodyfluid
Proper
functioningof
nerves
Regulation
ofheartbeat

12. a.Made up of cellulose
b.Prevent constipation

13. a. Solvent for many
substances in the
body
b.Regulate body
temperature

14. 1. A balanced diet contains the right amount of the
seven classes of food to meet the daily
requirements of the body.
2. Abalanced diet is necessary for:
a. supplying the required energy
b. balanced body growth
c. maintaining the health of the body
d. preventing deficiency diseases such as scurvy
and rickets

15. FACTOR THEGROUP REASON
REQUIRINGMORE
ENERGY
A.Sex Menrequiring Menaremore
moreenergyof active
thesameage
andbodysize
B.Age Babies,children Thisgroupis
andteenagers moreactiveand
requiremore thelifeprocess
energy arefaster

16. FACTOR THEGROUP REASON
REQUIRINGMORE
ENERGY
c.Bodysize Bigsized Bigsized
individuals individuals
requiremore requiremore
energysize energyfortheir
comparedto lifeprocess.
smallsized
individuals.
d.Physical Anindividual Heavywork
activity whodoesheavy requiremore
workusesmore energyto
energy perform.
comparedto
anotherwho
doeslightwork

17. FACTOR THEGROUP REASON
REQUIRINGMORE
ENERGY
e.Weather Individualsliving Moreenergyis
inplaceswith requiredto
coldweather maintainthe
requiremore body
energy temperatureina
comparedto coldplace.
individualsliving
inplaceswith
warmweather

18. 1. The calorific value of food is the total energy
produced when one gram of food is completely
burnt.
2. The quantity of energy in a food is measured in
calorie (cal) or joule (j)
3. 1 calorie (cal) = 4.2 joule (j)
1 kilocalorie (kcal) = 4.2 kilojoules (kJ)

19. Digestion
1. Digestion is the process of breaking down
complex food to simple molecules for absorption
the blood circulatory system.
2. Digestion take place in two stages:
a. physical digestion – big pieces of food are
broken down into smaller pieces by teeth
b. chemical digestion – enzymes break up
complex food molecules into smaller molecules

20. 3. Enzymes are proteins that speed up the process
of digestion. Enzymes break up complex food molecules
to smaller and simpler molecules.
4. Characteristic of enzymes
a. enzymes are small quantities only
b. enzymes are not destroyed at the end of digestion
c. specific enzymes act only in specific acidic or alkaline
conditions
d. specific enzymes act only on specific foods
e. enzymes function best at normal body temperature (370 C)
Enzymes are destroyed at high temperature.

21. 1. The digestive system consists of all the organ in
the body that help in the digestion of food.
2. The alimentary canal is made up of the mouth,
oesophagus, stomach, small intestine, big
intestine and anus (starts from the mouth and
ends at the anus).

22. 3. Summary of the digestive system
mouth oesophagus stomach small
intestine big intestine anus
4. Food is pushed along the alimentary canal by the
muscular walls that contract and expand alternately
through the process of peristalsis.

23. Mouth
Oesophagus
Stomach
Duodenum
Lower part of
small intestine
Appendix

24. 1. Food is chewed and broken up into small pieces by
the teeth.
2. Small pieces of food have a wide surface area for
the saliva to act upon.
3. The salivary gland secretes saliva that is alkaline
and contains salivary amylase enzymes.
4. Salivary amylase digests starch into maltose
(sugar)
amylase
starch maltose

25. 1. Food is pushed through the oesophagus into the
stomach by the alternating r contraction and
relaxation of the oesophagus.
2. This process of alternating muscular contraction
and relaxation is known as peristalsis.

26. 1. Food is mixed with gastric juice in the stomach.
2. Gastric juice is secreted from the cells of the stomach
wall. Gastric juice contains:
a. hydrochloric acid
b. enzymes (rennin and pepsin)
3. The function of hydrochloric acid include
a. providing an acidic medium for enzymic action.
b. killing bacteria found in food
c. neutralising the alkaline property of saliva

27. 4. Pepsin digest protien to peptones / polypeptides
Protien pepsin peptones/ polypeptides
5. Rennin coagulates milk in the stomach to help in the enzymic
enzymes.
rennin
Liquid milk protiens solid milk protiens

28. 1. The duodenum is the first part of the small intestine.
2. The duodenum received bile and pancreatic juice.
3. The function of bile are:
a. emulsification of fat
b. preparation of an alkaline medium for enzymic action
4. Pancreatic juice contains three types of enzymes:
a. maltase
b. protease
c. lipase

29. 5. The maltase digests maltose into glucose
maltase
maltose glucose
6. The protease digests peptones into amino acids
protease
peptones amino acids
7. The lipase digests fat into fatty acid and glycerol
lipase
fat fatty acids + glycerol

30. 8. Digestion is completed in small intestine.
9. The digest food is then ready to be absorbed through
the thin walls of the small intestine into the bloodstream.
10. Food digestion is completed in the small intestine.
11. The end products of digestion are
a. Carbohydrate - glucose
b. Protien - amino acids
c. Fats - fatty acids and glycerol .

31. 1. Water is reabsorbed in the big intestine
2. Undigested food is expelled from the body
through the anus as faeces.

32. 1. The inner surface of the small intestine has many
villi.
2. The villi increase the surface area for the
absorption of digested food.
3. Absorption is the movement of digested food into
the bloodstream

33. Villus
Blood capillary

34. Reabsorption of Water and Defecation
Residue from the
small intestine
Reabsorption of water
+ minerals + vitamins
Solid waste called faeces
Stored in the last part of
the large intestine
Defecation through the anus

35. Difficulty in defecation is called
constipation.
Prolonged and serious
constipation can lead to …..
• Hemorrhoids (piles)
• Cancer of the large intestine
Defecation is removal of faeces
from the body through the anus

36. Why causes constipation?
Not eating enough roughage Not drinking enough water
Cause
Constipation

37. 1. Therefore, constipation can be cured
by
• taking laxatives
• eating high fibre foods such as wholemeal cereals and
grains, fruits and vegetables
• taking more fluid
Remember, prevention is always better than curing

38. HEALTY EATING HABITS.
Unhealthy eating habits is the main cause of many diseases
• Too much sugar diabetes
• Too much salt high blood pressure
• Too much fat obesity, high blood cholesterol level, cancers
• Too much food obesity
• Too little food anorexia nervosa, bulimia
• Too little roughage constipation, haemorroids

39. So, cultivate healthy eating habits to stay healthy
• Eat a variety food according to the recommended amount
shown in a food guide pyramid.
Eat least
Eat most

40. • Eat in moderation. Balance food intake with exercise
• Choose nutritious food
Nutritious food Less nutritious food
• Fresh fruits • Junk food
• Fresh vegetables • Highly processed
food
• Wholemeal
cereal, grains or • Fast foods
bread
• Fizzy drinks
• Unpolished rice

41. • Read food labels
• Do not be misled by food advertisements
• Eat at regular time

42. Summary Chart
Nutrition
Food Healthy eating habits
Classes,
Food tests Calorific value
sources and
functions Balanced diet
Digestion
Absorption of Absorption of
digested food water and Defecation
dissolved minerals