Food

Chapter 3

Function of food

• All living things need food.

• The functions of food are:

1) To provide energy

2) To provide material for growth and

repair of cells

3) Protection against disease

Types of food

Carbohydrates:

Sugars(fruits, cakes, jams and sweets) and

starch(potatoes pasta and bread) provide energy.

Fibre(whole-grain bread, vegetables and cereals) prevents constipation.

Carbohydrates

Fats

Fats

Fats(milk, fatty meat) store energy,insulate the body against heat loss and protect vital organs.

Protein

Protein (meat, fish and eggs) are necessary for the growth and repair of cells.

Minerals and Vitamins

Minerals

Iron is necessary to make red blood cells.

Calcium is necessary for healthy bones.

Vitamins

Vitamin C is necessary for healthy teeth and gums

Vitamin D is necessary for strong bones

Scurvy

Types of food

Type of food Source Function Protein Meat Fish Eggs Growth and Repair of cells Carbohydrates Sugar Bread Potato Rice Energy Fats Butter, Oil, Energy

Insulation Protection

Vitamins (A.B,C D) Wheat Fish Fruit and Veg Healthy Body Minerals (Iron, Calcium) Vegetables, Milk Healthy Body

A balanced diet consists of the right amount of the six constituents, carbohydrates, protein, fats vitamins minerals and water to stay healthy

Food and energy

The energy content of food is given in kilojoules (kj)

The energy required from an average 14 year old is:

Boy- 12,000 kj

Girl- 10,000 kj

Different foods provide us with different amounts of energy.

Food PyramidThe food pyramid

shows roughly the amount of each common food types per day for the average child or adult for a healthy balanced diet.

Test for Starch

1)Add a few drops of Iodine to a test tube of Starch

Result

The Iodine turns blue black in colour

Test for Glucose

1)Add a few drops of Benedicts solution to a glucose solution.

Result

After heating the solution will turn a brick red colour

Test for Protein

1)Add some sodium hydroxide and a few drops of Copper Sulfate to a test tube containing milk.

Result

The solution will turn a purple/violet colour.

Test for Fats1) Rub a piece of food onto

some brown paper

2) Allow the paper to dry.

Result:

A translucent spot(allows light to pass through) is seen on the paper

To show the conversion of chemical energy to heat energy

1) Set up apparatus as shown in the diagram.

2) Record the temperature of the water.

3) Ignite the foods source and place it under the beaker of water.

4) After 1 minute remove the food and record the new temp of the water.

Result

As the food burned the chemical energy in the food was converted into heat energy.

Web sites

http://www.primaryresources.co.uk/science/foodgroups.htm

http://www.kelloggs-alarabi.com/english/teacher%20section/trail/foods.html#

http://library.thinkquest.org/5777/dig1.htm

http://kidshealth.org/kid/body/digest_noSW.html