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2.1 Classes of Food
Classes Functions Examples
Carbohydrates Supply main energy to body
sugars: cakes, cholates, fruits
starch: rice, bread, potatoes
cellulose: vegetables, fruit
glycogen (stored in the liver & muscle)
Fats Supply more energy & give heat to body butter, cheese, margarine
For growth, repair and replace damaged
meat, fish, milk, eggs, beans,
Vitamins Maintain good health vegetables & fruits
Minerals For proper growth & development of body meat, milk, banana, seafood, eggs
Fibre To stimulate peristalsis fruits & vegetables
Medium for chemical reaction in the body
waterRegulate body temperature
Transport digested food & waste materials
CHAPTER 2: NUTRITION
Excess carbohydrates stored as fat in the body.
Vitamins A, D, E, K – fats soluble
Vitamins B, C – Water soluble
Vitamins – required in small quantity for body
Vitamins Functions Examples
A To promote healthy skins & eyes
carrot, tomatoes, green
Dry skin , night
Maintain healthy skin & nervous
yeast, liver, vegetables
To increase immunity against
guavas, grapes, tomatoes, Scurvy
Maintain healthy skin, teeth,
citrus fruit, vegetables
Maintains healthy & strong teeth
milk, eggs, fish
Rickets, softening of
Promotes calcium & phosphorus
Maintain healthy reproduction
seeds, nuts, egg yolk, whole
K Blood clotting
liver, egg yolk, green
Minerals Functions Examples
Sodium Maintain body fluid balance
cheese, meat, table
Potassium For nerve & muscle activities bananas, fish, meat
Maintain strong & healthy teeth &
milk, eggs, anchovies, Rickets, Osteoporosis,
Helps blood clotting green vegetables prolong bleeding
Formation of haemoglobin in red blood
liver, egg yolk, meat Anaemia
Iodine Make the hormones of the thyroid seafood, seaweed Goitre
Help in muscle contraction, make
healthy cheese, milk, eggs
Rickets, tooth decay,
bones, and teeth weak muscle
Beri-beri (disease of nervous system)
Pellagra (skin disease)
Anaemia (shortage of red blood cell)
Scurvy (bleeding gums)
Rickets (stunted growth) Goitre (swollen
Kwashiorkor (lack of protein)
Classes Type of test Reagent Result
Starch Iodin test Iodine
brown colour Iodine change into blue
Benedict's test /
brick-red precipitate formed
Proteins Millon's test
white precipitate - red colour
milky solution or white emulsion
Balanced diet – Diet which contains all seven types of food classes in the right
quantities & proportions.
Factors affecting balanced diet
Factors Explanation Reason
babies, children, & teenagers need more Babies, children, and teenagers
energy than adults more active & life process faster
Men need more energy than woman Men are more active than woman
of the same age & body size
Big size individuals need more energy Big size individual need more
than small size individual energy for life process
Health Patients’ needs more energy than Patients need more energy to
condition someone who is healthy recover from diseases.
Type of Heavy work need more energy Heavy work need more
job than light work energy to perform
Climate Individual live in cold weather need more More energy required in cold weather
energy than individual live in warm weather to maintain body temperature
Calorific value of food
Human digestive system
1. Digestion – process of breaking down large food molecules into smaller molecules that can be
absorbed by body.
2. Physical digestion – breaking down food into smaller particles by teeth.
3. Chemical digestion – breaking down food by enzymes.
Mouth Oesophagus Stomach Duodenum
Anus Rectum Large intestine Small intestine
Mouth Cut & chews the food into smaller molecules
Oesophagus Channels food (bolus) to stomach through peristalsis action
Stomach Begins the digestion of protein
Duodenum Secret pancreatic juices to digest protein, carbohydrate, & fats
Small intestine Complete the food digestion and absorb end product of digestion
Large intestine Reabsorb water & minerals from indigested food
Rectum Store the faeces
Anus Removes faeces from body
Salivary glands Produce saliva which contain amylase enzyme
Liver Secrets bile to emulsify fats
Gall bladder Store bile which is secreted by liver
Pancreas Produce digestive enzymes (amylase, protease, lipase)
4. Peristalsis – Contraction & relaxation of digestive tract to channel the food throughout the
Organs Juices Enzyme Functions
Mouth Saliva (alkaline) Amylase Starch - Maltose
Gastric juice Protease Protein - Polypeptide or Peptone
(acidic) Casein/Rennin Liquid milk protein - Solid form
Kills bacteria in the food
Pancreatic juice Amylase Starch - Maltose
(secreted by pancrease) Protease Protein - Polypeptide or Peptone
(Alkaline) Lipase Fat - Fatty acid + Glycerol
Bile (alkaline greenish
fluid secreted by liver)
Emulsify fats & oils into globules
intestine Intestinal juice
Maltase Maltose - Glucose
Protease Peptone - Amino acid
Lipase Fat - fatty acid + Glycerol
1. Absorption of end product take place in small intestine through the diffusion process.
2. Length of small intestine – 6 metre. Walls of small intestine is folded to increase its surface
3. Features of small intestine:
a. Have many finger-like projections known as villi (singular: villus).
b. Have many blood capillaries to facilitate absorption.
c. Very long about 6 m allows greater absorption.
d. Very thin so that small molecules can enter the blood capillaries.
e. Moist lining enables food molecules to dissolve easily.
4. Vilus or Villli – the surface of small intestine covered with millions of tiny finger-like projections.
5. Functions of vilus – Absorb digestion food effectively.
Food class End product
Protein Amino acid
Fat Glycerol + fatty acid
Absorption of digested food
Water, minerals, vitamins are need not to
be digested because these food are very
small and simple molecules that can be
absorbed into body.
1. Undigested food enters the large intestine.
2. Reabsorption of water & minerals from undigested food (e.g cellulose, fibre) take place.
3. Defecation – process where faeces removed from body.
4. Faeces is formed and stored in the rectum. Then, removed through anus.
1. Good eating habits – Eating nutritious food in right quantities & proportion.
2. Healthy eating habits:
a. Eat plenty of vegetables & fruit.
Reabsorption of water & defecation
Good eating habits
b. Consume less sugar & salt
c. Eat in moderation
d. Drink plenty of water
e. Chew food thoroughly before swallowing
f. Eat nutritious food
g. Avoid junk food
3. Unhealthy eating habits:
a. Consume high sugar lead to diabetes
b. Consume high salt lead to blood pressure
c. Consume too much fat lead to high blood cholesterol and heart diseases
4. Constipation – difficulty to defecate hard faeces from body.
5. Causes of constipation – lack of water & roughage in diet. To avoid constipation, must eat
food such as fruits, vegetables, and grains.
6. Over weight/ Obesity – Excess body fat which can cause health problem such as diabetes,
hypertension, heart diseases, cancer, & failure in respiratory and excretory
7. Causes of obesity – Genetic, lack of exercise, unbalanced nutrition
8. Saturated fat is bad for body because fat will accumulate in the blood stream and cause
blockage of blood vessels and lead to heart attack and stroke.