3. Classes of food
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 disease
5. Carbohydrate
Made of carbon, hydrogen and oxygen
Includes sugar, starch, glycogen and cellulose
Smallest unit is glucose
Sources: Rice, potatoes, cereals, sweets, flour
Function: Provide energy
6. Protein
Made of carbon, hydrogen, oxygen and nitrogen
Some may have sulphur and phosphorus
Smallest unit is amino acids
Sources: Meat, fish, milk, eggs (animal protein)
: Beans, peas, vegetables (plant protein)
Function: Growth and repair body tissues
: Form enzymes, hormones, antibodies
: Source of energy during starvation
: Prevent kwashiorkor
7. Fats
Made of carbon, hydrogen and oxygen
Smallest units are glycerol and fatty acids
Sources: Butter, cheese, fatty meats (animal fat)
: Vegetable oil, margarine (plant fat / oil)
Function: Source of energy (x2 carbo.)
: Heat insulator (keep body warm)
: Protect organs from injury
: Dissolve fat-soluble vitamin (A, D, E, K)
8. Vitamins
Organic compounds required in small quantity
Vitamin deficient can cause diseases but excess
of vitamins can become toxins to body
Divided into:
a) Water soluble (Vit. B & C)
b) Fat soluble (Vit. A, D, E & K)
9. Vitamin Sources Effects of deficiency How to remember,,,
A Carrot,
tomato, cod
liver oil
• Night blindness • Source of vit A is basically from
many red / orange-coloured food
• Related to eyes
B Liver, eggs,
milk
• Beri-beri (nervous disorder)
• Pellagra (skin + mental + diarrhoea)
• Vit B Beri-beri
C Citrus fruits,
vegetables
• Scurvy
• Wound difficult to heal
• Low immune system
• Vit C sCurvy
D Liver, eggs,
milk, sunlight
• Rickets
• Osteomalacia
• Tooth decay
• Related to bones and teeth
E Wheat germ,
green
vegetable,
whole grain
• Sterility
• Anaemia
• Eczema (skin disease)
• The only vit related to sterility
and eczema
K Liver, green
vegetable,
eggs
• Slow blood clotting
• Anaemia
• Vit K is needed in blood clotting
process.
Remember some general info
suffice. No need to remember
the whole table. It’s KILLING!!
11. Minerals
Inorganic compounds required in small quantity
Needed for proper growth & development
Excess minerals are excreted through sweat and
urine
12. Mineral Sources Functions Deficiencies
Calcium Milk,
cheese,
anchovies
• Strong bones & teeth
• Muscle contraction
• Nerves
• Helps blood clotting
• Rickets
• Tooth decay
• Osteoporosis
• Weak muscles
• Muscle cramps
Phosphorus
Iodine Seafood
• Prevent goitre
• Form thyroxine (hormone in thyroid)
• Control body growth
• Goitre
Iron
Spinach,
liver,
cereal
• Formation of haemoglobin in red
blood cells
• Anaemia
Sodium
Salt,
meat,
cheese
• Maintain water balance in body
• Normal function of muscle & nerves
• Muscle cramps
• Weak muscles
• Paralysis
Potassium
Banana,
fish, meat
Remember some general info
suffice. No need to remember
the whole table. It’s KILLING!!
14. Water
Average 8 glasses per day
Lost a lot of water from urine and sweat
Source: Drinking, fruits and vegetables
Importance: 70% body is made of water
: Helps in digestion and excretion
: Controls body temperature
: As solvent for chemical reaction in
body
15. Food Test Procedure Observation
Starch Iodine test • 2cm3 starch solution + few
drops iodine solution
• Brown colour of iodine
turns blue-black
Glucose Benedict’s test • 2cm3 glucose solution +
2cm3 Benedict’s solution
• Heat in water bath
• Light blue colour of
Benedict’s solution turns
brick-red precipitate
Protein Millon’s
reagent test
• 2cm3 albumen + 2 drops
Millon’s reagent
• Heat in water bath
• White precipitate is
formed when Millon’s
reagent is added
• White precipitate turns
red precipitate on heating
Fats Emulsion test • Ethanol + 5 drops cooking
oil
• Shake and let it stand for
2 minutes
• Milky solution (emulsion) is
formed
Spot test • 1 drop of cooking oil on
filter paper
• Allow to dry
• Translucent spot formed
Food test
16.
17. Balanced diet – all classes of food in correct proportion
Cereals,
carbohydrate
(8-11 servings)
Fruits & vege (at
least 5 servings)
Meat and proteins
(2-3 servings)
Fats and sugar (little)
Exercise and
plenty of water
is a must too!!
Important to maintain health and
prevent various deficiency diseases
19. a) Age – A growing child needs more protein and calcium
than adult
b) Size – A big sized person normally needs more food
than a small sized person
c) Gender – Boys generally needs more food than girls
as they are usually more active
20. d) Jobs – A person doing heavy work needs more food
than a person doing light work for more energy
e) Climate – People in cold countries need more food
than those in warm countries to keep them warm
f) Health – People with health status needs to be
careful with their diets
21. Calorific value
Energy stored in food is measured in calorie (cal)
or joules (J).
Calorific value of food is the amount of energy
released from 1 gram of a particular food.
1 cal = 4.2 J
1 000 cal = 1 kcal
1 000 J = 1 kJ
In complete combustion:
a) Carbohydrate gives 17 kJ/g energy
b) Proteins give 17 kJ/g energy
c) Fats give 39 kJ/g energy
22.
23.
24. Digestion
The process of breaking down food into soluble and
diffusible molecules
Carried out by enzymes, a special protein produced
by body to speed up chemical reaction in body
3 main types of digestive enzymes:
a) Amylase (help digestion of carbohydrate)
b) Protease (help digestion of protein)
c) Lipase (help digestion of fats)
Non-digestive enzymes that help in digestion:
a) Hydrochloric acid (stomach)
b) Bile (liver and stored in gall bladder)
25.
26. Mouth
Salivary amylase /
ptyalin
Starch Maltose
Don’t forget the word “SALIVARY”. Salivary amylase is
in the mouth. Amylase is in duodenum… There’s a
difference!!
Stomach (gastric juice)
• Protease
Protein Polypeptides
• Renin
Caseinogen (soluble milk) Casein (insoluble
milk)
• Hydrochloric acid (not enzyme)
Stop actions of enzymes from saliva and kills
bacteria in food
To remember enzymes in
stomach, remember Power
Rangers – Protease & Renin.
So, there are Power Rangers in
your stomach!! @@
Duodenum - first part of small intestine
(bile + pancreatic juice)
• Bile (from liver and stored in gall bladder)
– not enzyme
Emulsify fat, neutralise acid from stomach &
provides alkaline medium for digestion
• Protease (from pancreas)
Polypeptides Peptides
• Amylase (from pancreas)
Starch Maltose
• Lipase (from pancreas)
Fat Fatty acid + Glycerol
All enzymes are involved in
duodenum.
Small intestine (intestinal juice)
• Maltose Glucose
• Peptides Amino acids
• Fat Fatty acids + Glycerol
All food are broken down to
their smallest unit.
Food is churned into a bolus and passed down through oesophagus via peristalsis
Partially digested food in
stomach is called chyme
27.
28. Absorption
Digested food (glucose, amino acids, fatty acids
and glycerol) and vitamins are absorbed by villi of
small intestine via diffusion into bloodstream
Large intestine
Small intestine
29. Adaptations of small intestine:
a) Has a lot of villi on its surface. Each villus
surface has more tiny projections (microvilli).
This increases 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
30.
31.
32. Reabsorption of water and defecation
Undigested food, minerals and water enters large
intestine.
Most water and minerals are reabsorbed in the
large intestine.
As water is absorbed, the mixture becomes solid
waste known as faeces.
Faeces is stored in rectum before being expelled
via anus. This process is known as defecation.
Lack of fibre and water will cause constipation.
33.
34. What does healthy eating habits means to you?
Some issues regarding healthy eating habits such as
vegetarians and health status.
Effects of unhealthy eating habits.
