Nutrition f1 igcse

FORM 2: CHAPTER 2 NUTRITION
CHAPTER 2CHAPTER 2
NUTRITIONNUTRITION

CLASSES OF FOOD
 CARBOHYDRATE
 PROTEINS
 FATS
 VITAMINS
 MINERALS
 WATER
 FIBRE

CARBOHYDRATE
 Organic compound: carbon, hydrogen, oxygen
 Include sugars (sweet foods), starch (starchy
foods) and cellulose (plant cell wall)
 Functions of carbohydrate:
 To supply energy
 As stored food:
*excess glucose glycogen
starch
In animals
In plants
(stored in liver
and muscle)

Test for starch and glucose

PROTEINS
 Organic compound: carbon , hydrogen,
oxygen & nitrogen
 Made up of large number of subunits called
amino acids
 Not all amino acids can be made by our body
cells
 Source:
 Meat, fish, egg, dairy products (animal protein)
 Soy bean, legumes (plant protein)
(sometimes sulphur & phosphorus)

PROTEINS (CONT)
 Functions:
 Growth and repair of the body tissue
 Formation of enzymes, hormones, heamoglobin and
antibodies (protein compounds)
 Provide energy (proteins can be broken down into
glycogen during lack of carbohydrate & fat)

Test for proteins

FATS
 Organic compound: carbon, hydrogen, oxygen
 Combination of fatty acids and glycerol
 Stored under skin or around organs in the body
 Fats are solid in room temperature, oil is liquid
in room temperature
 Sources: butter, cheese, margarine, palm oil,
ghee.

FATSFATS (CONT)(CONT)
 Functions:
 Keep us warm (heat insulator)
 Protect organs from damage
 Transport vitamins (A, D, E, K)
 Store lots of energy

Test for fats

VITAMINSVITAMINS
 Organic compound
 Needed small amount for our body
 Have two types:
 Water soluble: vitamins B and C
 Fat soluble: vitamins A, D, E, K

 Source: milk, carrot,
cod liver oil, eggs
 Important for good
vision
 Deficiency can
cause night
blindness, dry and
scaly skin

 Important for
healthy skin and
good nerve
function
 Deficiency can
cause beri-beri
(damage of
nervous system)
and pellagra
(skin disease)

 Beri-beri diseaseBeri-beri disease

 Important for :
 healthy gums and
skin
 prevents infections
 Deficiency can
cause:
 scurvy
 Easy to get coughs
and flu

 Scurvy diseaseScurvy disease

 Important for
strong bones
and healthy
teeth
•Deficiency can cause rickets (dental decay
and weak bones)

 Rickets diseaseRickets disease

 Important for
healthy
reproductive
system
 Deficiency can
cause
 Sterility
 poor muscle and
nerve functions

 Important for
blood clotting
 Deficiency can
slow clotting of
blood

MINERALSMINERALS
 Inorganic substances
 Needed in small amount in our body
 Excess minerals are removed from the body
through sweat and urine

 Functions:
 Formation of
strong bones
 Blood clotting
 Good muscle
and nerve
function
 Deficiency diseases:
- Rickets - Prolonged bleeding
- Osteoporosis - Muscular cramp

SODIUMSODIUM
 Deficiency disease:
 Muscle cramps
 Functions:
 Important component of
body fluid
 Proper nerve function

IRONIRON
 Anaemia
 Functions:
 Formation of
haemoglobin

IODINEIODINE
 Deficiency
disease:
 Goitre (swelling
of thyroid
glands)
 Functions:
 Needed to
make
hormones of
thyroid glands

PHOSPHORUSPHOSPHORUS
 Rickets and weak
bones
 Functions:
 Formations of strong
bones

POTASSIUMPOTASSIUM
 Muscle tiredness
 paralysis
 Functions:
 Healthy nervous system

WATERWATER
 70% of body weight
 Main component of blood and body fluid
 Dissolve lots of chemicals in our body and
allows the chemical to react
 To eliminate waste substances
 To regulate body temperature

FIBREFIBRE
 Known as roughage
 Made of cellulose from plant cell wall
 Source: Fruits, vegetables and cereal
 Fibre cannot be digested by human
 Fibre can hold lots of water, prevent
constipation

THE IMPORTANCE OF ATHE IMPORTANCE OF A
BALANCED DIETBALANCED DIET
 All food we eat everyday is known as diet.
 A balanced diet is a diet that contains all classes
of food in the right quantity and ratio according
to our body needs.
 Each person needs different amount of food.

 7 factors that affect a balanced diet:
1. Body size
2. Age
3. Gender
4. Occupation
5. Physical activity
6. Climate
7. Health

GROUP AGE SEX
BODY
ACTIVITY
ENERGY
REQUIREMENTS (Kj)
CHILD
5 FEMALE MODERATE 6 800
5 MALE MODERATE 7 600
ADOLESCENT
ADULT
25 MALE ACTIVE 10 500
25 MALE ACTIVE 14 000

 A balanced diet is important to:
 Ensure body growth
 Maintain optimum body health
 Repair and replace old or damage tissues
 Ensure enough energy for the body according its
needs
 Diet imbalance in the long run causes a person
to contract deficiency diseases or is known as
malnutrition

CALORIFIC VALUE OF FOODSCALORIFIC VALUE OF FOODS
 The energy that is stored in food is referred to asThe energy that is stored in food is referred to as
calorific value or energy value of foodcalorific value or energy value of food
 TheThe calorific value of foodcalorific value of food is defined as theis defined as the
amount of energy released from 1 gram of aamount of energy released from 1 gram of a
particular type of food.particular type of food.
 The calorific value of food is measured inThe calorific value of food is measured in caloriescalories
(cal) or joules (J)(cal) or joules (J)
 1 calorie = 4.2 joules1 calorie = 4.2 joules
 1000 calories (cal) = 1 kilocalorie (kcal)1000 calories (cal) = 1 kilocalorie (kcal)
 1000 joules (J) = 1 kilojoules (kJ)1000 joules (J) = 1 kilojoules (kJ)

How to calculate the calorific value of
food?
Example:
The calorific value of 100 g of fried noodles
is 595 kJ. Asmah eat 250 g of fried noodle as
her breakfast. So, the calorific value of the
food that she eat is:
100 g = 595 kJ
250 g = ?????
1487.5 kJ

Estimate the calorific value for the
following meals
MEAL 1
1 plate of nasi lemak
2 pieces of doughnut
1 cup of coffee
MEAL 2
1 piece of egg banjo
1 glass of chocolate milk
2558 kJ
2367 kJ

HUMAN DIGESTIVE SYSTEMHUMAN DIGESTIVE SYSTEM

MOUTHMOUTH

Premolar
Premolar

THE MAIN FUNCTION
 MOUTH: Keeps the food for chewing
 TEETH: Cut the food into small pieces
 SALIVARY GLANDS: Produce saliva containing
digestive enzyme (amylase)
 TONGUE: Tastes the food
 OESOPHAGUS: Channels the food from the mouth
into the stomach
 STOMACH: Produces digestive enzymes to digest the
food
 DUODENUM: Digests the food with the help of
enzymes from the pancreas

 PANCREAS: Produces digestive enzymes
(amylase, protease and lipase)
 LIVER: Produces bile for emulsifying fats
 GALL BLADDER: Stores bile from the liver
 SMALL INTESTINE: Produce digestive
enzymes and completes the digestion of food
 LARGE INTESTINE: Absorbs water from
the undigested food
 RECTUM: Keeps the faeces
 ANUS: Lets out the faeces

 The digestive system consists of all the organs
which take part in the digestion of food.
 The alimentary canal consists of the parts
through which food passes from the mouth to
the anus.
 Food passes through the alimentary canal along
the following pathway:
 Mouth → oesophagus → stomach →
duodenum → small intestine → large
intestine →anus

THE DIGESTION OF FOOD
 Process of changing the food eaten from large
complex molecules to small simple molecules which
can pass through the cell membranes into the cells of
the body.
 The physical digestion (process) : Food is broken into
small pieces (chewing by teeth, churning of food in
stomach)
 The chemical process: Large complex of food
molecules are changed into small and simple
molecules which can be absorbed by the body (action
of enzymes on food)

MOUTH

MOUTH
 The food in the mouth is first cut into small
pieces by the teeth and mixed with the saliva
 The small pieces of food provide a larger
surface area for the amylase enzyme in the
saliva to act on the starch.
 The amylase changes the cooked starch into
maltose.

OESOPHAGUS

OESOPHAGUS
 The partly digested food is swallowed into
the oesophagus.
 Peristalsis of the wall of the oesophagus
(contraction and relaxation of the
muscular wall) pushes the food down the
oesophagus into the stomach.
 Food is push downwards

STOMACH

STOMACH
 The food is mixed with gastric juice produced
by glands in the wall of the stomach.
 Gastric juice contains hydrochloric acid and
enzymes (protease).
 The hydrochloric acid
- neutralises the alkali in the saliva
- prepares an acidic medium for the enzymes to
act on the food.
- It also kills bacteria in the food.
- Activates the protease

 Protease digests proteins into polypeptides and
peptones.
 Mucus protects the stomach walls
 The mixture of food and gastric juice formed
the chyme (semi solid food)
STOMACH

DUODENUM

DUODENUM
 The duodenum is the first part of the small intestine.
 The food is mixed with bile and pancreatic juice.
 Bile:
- a thick alkaline liquid produced by the liver and
stored in the gall bladder
- does not contain any enzyme.
- neutralises the acid in the food from the stomach
(acidic chyme)
- Emulsifies oil into droplets so that it is easier for
any enzyme to act on it.

 Pancreatic juice is very alkaline.
 It contains three enzymes — amylase,
protease and lipase.
 Amylase: changes starch into glucose
 Protease changes proteins into amino
acids.
 Lipase changes fats into fatty acids and
glycerol.
DUODENUM

SMALL INTESTINE

SMALL INTESTINE
 The second part of the small intestine is called
the ileum.
 Digestion is completed in the ileum.
 Secretes the intestinal juice contains maltase,
protease and lipase.
 Maltase: breaks down maltose to glucose
 Protease: breaks down proteins and peptones
into amino acids.
 Lipase: breaks down fats into fatty acid and
glycerol

END PRODUCTS OF DIGESTION
 CARBOHYDRATES
STARCH →MALTOSE → GLUCOSE
 PROTEIN → POLYPEPTIDES /
PEPTONES → AMINO ACID
 FATS → FATTY ACIDS + GLYCEROL

ABSORPTION OF DIGESTED FOOD
 Completed in the small intestine (ileum)
 The small intestine contains:
(a) simple sugars (from the digestion of
carbohydrates),
(b) amino acids (from the digestion of proteins),
(c) fatty acids and glycerol (from the digestion of
fats),
(d) vitamins and minerals (do not need any
digestion),
(e) fibre (indigestible food),
(f) water.

 The digested food, vitamins and minerals are
absorbed by structures called villi (singular:
villus) on the inner wall of the intestine.
 Villi are very tiny projections; increase the
surface area for the absorption of food.
 Villi are richly supplied with blood vessels to
carry away the absorbed food substances to all
parts of the body.

VilliVilli

 Digested food absorbs to the bloodstream by
diffusion → liver → heart → all over the body
 During respiration, glucose is oxidised in the
cells to release energy, with carbon dioxide and
water as waste products.
 During assimilation, amino acids are used to
build new cells or repair damaged cells.

 Excess glucose is stored as glycogen in the
liver.
 Excess amino acids are decomposed
(deaminated) by the liver into urea and excreted
in the urine.
 Excess fats are stored under the skin or around
organs such as the heart and kidneys.

REABSORPTION OF WATER AND
DEFECATION

 The digested food substances have been absorbed
by the small intestine.
 The residue consist of water, undigested food,
mucus and digestive juices. Bacteria are present in
large numbers in the large intestine.
 The colon of the large intestine absorbs the water ,
vitamins and mineral salts from the food residue,
leaving behind solid waste material (faeces)

 The faeces is stored in the rectum and will be
thrown out through anus by the action of the
muscular wall.
 The process of getting rid of the faeces from
rectum is known as defecation.

CONSTIPATION
 Difficulty in removing undigested food from the.
 Can be avoided by eating food rich in fibre
(roughage), drinking plenty of water and exercise
regularly.
 Roughage helps the food to pass through easily
 Without roughage, the food will move slowly and
contains in the large intestine longer in time
 Can cause cancer, piles

EATING HABITS
 We should also chew the food well before
swallowing it.
 We should eat clean healthy food.
 Food contaminated with bacteria can cause
diarrhoea and food poisoning.
 Diarrhoea makes the intestine incapable to
reabsorb the water
 Lead to dehydration

HEALTHY EATING HABITS
Unhealthy eating habits leads to:
 Cardiovascular disease
 Cancer
 Obesity
 High blood pressure
 Anorexia nervosa

Something to think….Something to think….
 The generous distribution of food forThe generous distribution of food for
under privilegesunder privileges
 Cultural practices in diningCultural practices in dining
conforming to sensitivities andconforming to sensitivities and
religious beliefs.religious beliefs.

Nutrition f1 igcse

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