chapter 2 - classes of food

8/12/2019 Chapter 2 - Classes of food

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Chapter 2NUTRITION


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IMPORTANCE OF FOOD

Supplying with energy

Supplies materials to repair

tissues and build new cellsFood can be classified as follows


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FOOD CLASSIFICATION

carbohydrates fats minerals

water protein vitamin

fibre


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CARBOHYDRATES

Carbohydrates include the following

group of substances

CARBOHYDRATES

SUGAR

SIMPLE

SUGAR

E.G GLUCOSE

COMPLEXSUGAR

E.G SUCROSE

STARCH CELLULOSE GL


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Carbohydrate are present in various forms, such as:

i. starch, which is stored in plants.(bread, potatoes)

ii. Sugars, which are sweet and soluble in water.iii. Cellulose, which is found in plant cell walls andcannot be digested.(vegetable and fruits)

iv. Glycogen, which is found in liver and muscles.

Food rich in carbohydrate include rice; potato, sugar,

bread, and banana. Carbohydrate is our main source of energy.

Carbohydrate supplies us with energy to carry out dailyactivities such as walking, breathing, and working.


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PROTEIN Protein is made up of carbon, hydrogen, oxygen, and

nitrogen.

Sometimes protein can also contain phosphorus andsulphur.

Food rich in protein includes fish, milk, meat, egg whiteand nuts (groundnuts and soya bean). Proteins arerequired for building new cells for growth, to replacedamaged tissue.

Growing children require a lot of protein. Lack ofprotein will cause a disease know as kwashiorkor(stunted growth).


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FAT Fat is made up for carbon, hydrogen and oxygen but the ratio is

different from that of carbohydrate.

Food rich in fats includes palm oil, butter and egg yolk.

Fat produces twice the amount of energy compared withcarbohydrate of the same weight.

The function of fat include:

a. supplying energy,

b. as and insulator of heat to reduce heat loss from the body,

c. protecting the internal organs such as the kidneys and the

d. dissolving some vitamins in the body like vitamin A, D, E an


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VITAMINS

Vitamins are required in small quantities only.

Vitamins are classified into two groups

a. vitamins soluble in water vitamin B and C ,

b. vitamins soluble in fat- vitamin A, D, E and K

Vitamins protect the body from various types ofdiseases and maintains the health of the body.


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VITAMIN A

Egg, milk, cod liver, oil, carrot, papaya

- for growth and to promote healthy skin

- for good vision

- night blindness- dry and scaly skin


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VITAMIN B

yeast, egg, milk,tomato, liver, nuts- promotes the effectivefunctioning of the

nervoussystem

- control the supply ofcarbohydrates to themuscleand nerve cells

- beri-beri (injury to the nervous systemandparalysis)

- pellagra

- anaemia


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VITAMIN C

lime, citrus fruits,tomato, carrot ,papaya,

greenvegetables- increase immunity against disease

- promotes healthy skin

- scurvy (gusi merah)

- anaemia

- low resistance to infections (especially the

flu)


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VITAMIN D

egg, milk, cod liver oil

- helps in the absorption of

calcium and phosphorus in the smallintestines

for the growth of strong bones and teeth.

- rickets (weak and curved bones)

- tooth decay


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VITAMIN E

vegetable oil, palm oil,

egg, liver, milk

- maintains a healthy reproductivesystem

- sterility

- infertility


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VITAMIN K

maize, sunflower seeds,tomato, greenvegetables

- necessary for the clotting of blood.

- blood slow to clot


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MINERAL

minerals are simple chemicals usuallyfound in the body.

our bodies need more calcium andphosphorus than the minerals.(because

they help to form strong bones and teeth)

minerals are needed for good health.


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CALCIUM

milk, eggs,vegetables, cheese

forms strong bones and teeth

helps blood to colt

Rickets ( soft bones )Brittle bones and teeth

poor blood clotting


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SODIUM

common salt,

balances body fluid

muscle

cramps


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IRON

liver,, meat, eggs,vegetables

forms haemoglobin in red

blood cells

anaemia


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IODINE

seafood, vegetables,

iodinised salt

produces hormones in the thyroid gland

Goitre


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PHOSPHORUS

meat, milk, eggs,beans

forms strong bones and teeth

rickets

dental

decay


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POTASSIUM

meat, fish, cereals

maintains a healthy nervous system

muscle

cramps


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FIBRE

Fibre is made up of cellulose which cannobe digested by the body.

A shortage of fibre in our daily diet cancause constipation and sometimes even

bowel cancer.

Vegetables, fruit, beans, lentils and brownbread are examples of food rich in fibre.

WATER


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WATER approximately 65% to 70% of a persons body weig

made up of water.

The body obtains water when we drink water and when we consume fruits and vegetables.

Water is needed by the body for:

a. helping in the digestion of food

b. transporting digested food substances

c. transporting excretory products such as urea.

d. maintaining the concentration of blood.

e. maintaining the body temperature

f. all metabolic processes


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A BALANCED DIET Diet refers to the food and drinks that we consume

daily.

A balanced diet is one which contains

carbohydrates, proteins, fats, minerals, vitamins,water and fibre in the correct quantities andproportions.

A balanced diet is necessary for:

a. supplying the required energy

b. balanced body growthc. maintaining the health of the body

d. preventing deficiency diseases such as scurvyand rickets.

A balanced diet varies according to ones


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GENDER

men required more energycompared to

women of the same age and body

size.men are more active


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AGE

babies, children and teenagers requiremore energy compared to adults or theelderly.

Example: the heartbeat of baby is 100

beats a minute compared to an adultwho has 75 beats per minute.

this group is more active and the lifeprocesses are faster.


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BODY-SIZE

big-size individuals require moreenergy compared to small-sizedindividuals.

big-sized individuals require moreenergy for their life processes


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JOB/PHYSICAL ACTIVITY

an individual who does heavy workuses more energy compared toanother who does light work.

heavy work requires more energy toperform


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CLIMATE

individuals living in places with coldweather require more energycompared to individuals living inplaces with warm weather.

more energy is required to maintainthe body temperature in a coldplace


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STATE OF HEALTH

Sick person requires more energy torecover; therefore he needs foodwith more nutrition

Light exercise to sweat and releasewaste


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The calorie value of food Energy in food measured in joules (J) or calories

1 calorie (cal) = 4.2 joules (J)

1 kilocalorie (kcal) = 4.2 kilojoules (kJ)

The calorific value of food is the amount of heatenergy released when one gram of food is comburnt in the air.

The calorific value of food is measured in kilojougram (kJ/g) or kilocalories per gram (kcal/g)

The calorific value differs for different types of foTable below shows the calorific value of some ofood that we eat daily.


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FOOD CALORIES

NASI LEMAK 644

ROTI CANAI 360

WANTAN MEE 409

MEE GORENG 660

PLAIN RICE 177

THE TARIK 83


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HUMAN DIGESTIVE SYSTEM

Digestion is the process of breaking downlarge and complex food substances intosmaller, simpler molecules. Thesemolecules are soluble and can be

absorbed by body cells. the digestive process occurs in a system

which is called the digestive system.


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Mouth

chew and grinds food using the teeth

digests cooked starch. The amylase enzymes inthe saliva change cooked starch to maltose.

The salivary glands secrete saliva which containan enzyme called amylase.

Amylase digests starch and convert it to maltose(a type of sugar)


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Oesophagus

bolus-shaped food is moved from the mouth tothe stomach along the oesophagus by wave-like muscular contractions called peristalsis


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Stomach

holds food, secretes gastric juices whichbegin the digestion of protein

secretes acids contains hydrochloric acidwhich kill the bacteria in food.


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Duodenum

receives bile from the liver and pancreaticjuice from the pancreas.

Digestion and absorption of food.

i i


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Small intestine

secretes intestinal juice which completes thedigestion of protein, carbohydrates and fat.

Absorbs end products of digestion into theblood.


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Large intestine

absorption of most of the remaining water

and minerals.

Rectum

stores faeces

Anus

removes faeces through


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MOUTH

LIVER

PANCREAS

RECTUM

OESOPH

STOMAC

SMALL IN

LARGE IN

ANUS

DUEDON

The process of digestion in the alimentary canal


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The process of digestion in the alimentary canal

a. physical digestion

involves the mechanical process of breakingdown large pieces of food into smallerparticles using the teeth and the churningmovements of the alimentary canal.

b. chemical digestion

involves the action of various enzymes in

breaking down complex food molecules.These complex molecules are insoluble butthe end products of chemicals digestion aresimpler molecules which are soluble.

M th


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Mouth

Digestion begins in the mouth.

ii. The teeth chew and grind food into smallerparticles.

iii. the salivary glands secrete glands secretesaliva which contains an enzyme calledamylase.

iv. Amylase digests starch and converts it tomaltose, a type of sugar.

v. The wave-like contractions of the oesophagumuscles are known as peristalsis.

St h


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Stomach in the stomach, food is mixed with gastric juices

Gastric glands in the stomach wall.

Gastric juices contains hydrochloric acid andenzymes (rennin and pepsin) .

The functions of hydrochloric acid include:

a. Hydrochloric acid stops the action of the

enzymes in saliva.b. It also kills bacteria in food.

Enzymes in the gastric juices start the digestion oprotein.


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Protease > protiens to peptones

Rennin Liquid milk proteins solid milk proteins

Partially digested food is then released into theduodenum.

Duodenum & small intestine


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Duodenum & small intestine The duodenum is the first parts of the small

intestine.

The duodenum receives bile and pancreaticjuice. (bile is stored in the gall bladder)

The function of bile:

a. Emulsifications of fat i.e. breaking up largefatty globules into small droplets for enzymicaction.

b. Preparation of an alkaline medium forenzymic action.

The pancreatic amylase digests starch into

maltose

Th li di t f t i t f tt id d


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The lipase digests fat into fatty acid andglycerol.(duodenum)

The protease digests protein/peptones into

amino acids. The small intestine (ileum) produces enzymes

which digest maltose into glucose (simple sugar

Digestion is completed in the small intestine.

The digested food is then ready to be absorbedthrough the thin walls of the small intestine intothe bloodstream.

Absorption of the products of


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Absorption of the products ofdigestion

Absorption is the process when the end productof digestion enters the bloodstream through thesmall intestinal walls.

The inner surface of the small intestine (6 metreslong) covered with millions of small projections

about 1mm long. These projections are calledvilli @ villus.

Food that has been digested into its most simpleform is absorbed by the villi @ villus on the smallintestinal walls into the bloodstream.

The efficiency of absorption of digested food at


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The efficiency of absorption of digested food atthe small intestine can be increased by:

a. more villus to increase surface area

b. villus with very thin walls Each villus has a network of a blood capillaries

and a lacteal.

Glucose, amino acids, minerals and water-solube vitamins are absorbed into the blood

capillaries.

Fatty acids, glycerol and fat-soluble vitamins(vitamin A, D, E and K) are absorbed into thelacteal.

REABSORPTION OF WATER AND


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REABSORPTION OF WATER ANDDEFACATION

The main function of big intestine is to reabsorb water. The substances that enter the big intestine consist of

water and undigested food substances like cellulosefrom the fibre of vegetables and fruits (roughage)

Water is reabsorbed from these undigested food

substances. Undigested food materials together with water is passed

to the colon(first part of the large intestine)rectum is thelast portion of the large intestine

D f ti


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Defecation

Undigested food in the big intestine is expelledas faeces through the process of defecation.

When the rectum is full of faeces, the rectumundergoes peristalsis and assisted by abdominacontraction, will push the faeces through theanus to be expelled.

If an individual has problems passing motion, heor she is said to be constipated.

Constipation takes place because of the lack owater in the diet.

THE FOOD PYRAMID


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THE FOOD PYRAMID


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Healthy eating habits will help maintain ahealthy body.

2. Unhealthy eating habits cause various healthproblems

excessive nutrient health problems


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excessive nutrient health problems

Sugar tooth decay, obesity, diabetes

Salt high blood pressure, heart problems,

kidney damage

fat/oil heart problems, high blood pressure

lack of nutrient health problems

Protein kwashiorkor in children

Roughage Constipation

Vitamins lower immunity to diseases

chapter 2 - classes of food

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