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FORM 2: CHAPTER 2 NUTRITION
CLASSES OF FOOD
CARBOHYDRATE PROTEINS FATS VITAMINS MINERALS WATER FIBRE
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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)
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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)
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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)
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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.
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FATS FATS (CONT)(CONT)
Functions: Keep us warm (heat insulator) Protect organs from damage Transport vitamins (A, D, E, K) Store lots of energy
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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
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Source: milk, carrot, cod liver oil, eggs
Important for good vision
Deficiency can cause night blindness, dry and scaly skin
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Important for healthy skin and good nerve function
Deficiency can cause beri-beri (damage of nervous system) and pellagra (skin disease)
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Important for : healthy gums and
skin prevents infections
Deficiency can cause: scurvy Easy to get coughs
and flu
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Important for strong bones and healthy teeth
•Deficiency can cause rickets (dental decay and weak bones)
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Important for healthy reproductive system
Deficiency can cause Sterility poor muscle and
nerve functions
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MINERALSMINERALS
Inorganic substances Needed in small amount in our body Excess minerals are removed from the body
through sweat and urine
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Functions: Formation of
strong bones Blood clotting Good muscle
and nerve function
Deficiency diseases:- Rickets - Prolonged bleeding
- Osteoporosis - Muscular cramp
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SODIUMSODIUM
Deficiency disease: Muscle cramps
Functions: Important component of
body fluid Proper nerve function
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IRONIRON
Deficiency disease: Anaemia
Functions: Formation of
haemoglobin
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IODINEIODINE
Deficiency disease: Goitre (swelling
of thyroid glands)
Functions: Needed to
make hormones of thyroid glands
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PHOSPHORUSPHOSPHORUS
Deficiency disease: Rickets and weak
bones
Functions: Formations of strong
bones
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POTASSIUMPOTASSIUM
Deficiency disease: Muscle tiredness paralysis
Functions: Healthy nervous system
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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
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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
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THE IMPORTANCE OF A THE 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.
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7 factors that affect a balanced diet:1. Body size2. Age3. Gender4. Occupation5. Physical activity6. Climate 7. Health
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GROUP AGE SEX BODY ACTIVITY
ENERGY REQUIREMENTS (Kj)
CHILD5 FEMALE MODERATE 6 800
5 MALE MODERATE 7 600
ADOLESCENT14 FEMALE MODERATE 9 200
14 MALE MODERATE 11 200
ADULT
25 FEMALE MODERATE 8 500
25 MALE ACTIVE 10 500
25 FEMALE MODERATE 9 800
25 MALE ACTIVE 14 000
65 FEMALE MODERATE 6 400
65 MALE MODERATE 8 600
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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
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CALORIFIC VALUE OF FOODSCALORIFIC VALUE OF FOODS
The energy that is stored in food is referred to as The 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 a amount 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 calories calories (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)
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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
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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
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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
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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
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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
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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)
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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.
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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
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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
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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
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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.
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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
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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
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END PRODUCTS OF DIGESTION
CARBOHYDRATES
STARCH →MALTOSE → GLUCOSE
PROTEIN → POLYPEPTIDES / PEPTONES → AMINO ACID
FATS → FATTY ACIDS + GLYCEROL
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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.
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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.
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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.
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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.
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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)
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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.
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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
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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
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HEALTHY EATING HABITS
Unhealthy eating habits leads to: Cardiovascular disease Cancer Obesity High blood pressure Anorexia nervosa
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Something to think….Something to think….
The generous distribution of food for The generous distribution of food for under privilegesunder privileges
Cultural practices in dining Cultural practices in dining conforming to sensitivities and conforming to sensitivities and religious beliefs.religious beliefs.