1.3.1 Function of Food

Why do we need food?

Food is needed for:

1.Energy

2.Growth of new cells and

Repair of existing cells, tissues, organs, etc.

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Food also supplies:

the materials and energy

for the processes of:

Metabolism

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Learning check

Why do we need food?EnergyGrowth of new cells and Repair of existing cells, tissues, organs, etc.

What is metabolism?Metabolism is the chemical reactions that occur in the cells of living organisms

What is continuity?Continuity of life is the ability of an organism to exist from generation to the next

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1.3.2 Chemical Elements

Elements in Food

What is Food made up of?

Food is made up of:

• Six chemical elementsC, H, O, N, P, S

• Salts of Na, Mg, Cl, K, Ca

• Three trace elements Fe, Cu, Zn 6

Chemical Elements and their Symbols

Calcium Ca Nitrogen N

Carbon C Oxygen O

Chlorine Cl Phosphorus P

Copper Cu Potassium K

Hydrogen H Sodium Na

Iron Fe Sulphur S

Magnesium Mg Zinc Zn7

Types of Food

The elements combine in different ratios to form different food components (biomolecules)

Food is made up of six different components

Water Proteins

Lipids Carbohydrates

Vitamins Minerals8

Learning check

What are the six different food components?

Water Proteins

Lipids Carbohydrates

Vitamins Minerals

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Food

• Food is any substance used by living organisms to provide energy, materials for repair and maintenance or to control metabolism

Humans are mainly made up of Water!

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Biomolecules

Biomolecules are complex molecules made up of different elements.

There are 4 main types of bio-molecules:CarbohydratesLipidsProteinsVitamins

Carbohydrates

Carbohydrates contain the elements

Carbon Hydrogen Oxygen

The general formula for a carbohydrate is

Cx(H2O)y

Ratio Hydrogen:Oxygen2 : 1 13

A common carbohydrate

General formula = Cx(H2O)y

When x = y = 6

We get the formula C6H12O6

What is the name of this monosaccharide carbohydrate?

Glucose

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Learning check

Name the three elements that make up carbohydrates

Carbon Hydrogen Oxygen

What is the general formula for a carbohydrate?

Cx(H2O)y

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Carbohydrates

Carbohydrates contain the elements

CarbonHydrogenOxygen

Usually in the ratio of 1C:2H:1O

They have twice as many hydrogen molecules as oxygen molecules

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3 Types of Carbohydrate

Monosaccharides

Disaccharides

Polysaccharides

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Monosaccharides

These are single sugar molecules simple sugarssoluble in watersweet to tastesmallest carbohydrate unit

Examples: glucose, fructoseFound in: fruit

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O

C C

C C

C

C

Disaccharides

These are

• two monosaccharide sugar units joined together – known as double sugar molecules

• soluble in water

• sweet to taste

Examples: sucrose, lactose, maltose

Found in: table sugar, milk19

Polysaccharides

These are• Many monosaccharide sugar molecules

joined together• Not soluble in water• Do not taste sweet

Example: starch, celluloseFound in: bread, pasta, cereals

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Learning check

Name the three types of carbohydrate

• Monosaccharides

• Disaccharides

• Polysaccharides

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Lipids

Lipids are a diverse group of substances which include

• fats (solid at room temp.)

• oils (liquid at room temp.)

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Structure of Lipids

They are made up of the elements carbon hydrogen oxygen

But not have the same ratios as carbohydrates.

They are made up of two main types of molecules

Fatty acids and Glycerol

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Learning check

Give examples and sources of:

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Examples Sources

Monosaccharides

Disaccharides

Polysaccharides

Glucose

Fructosefruit

Sucrose

Lactose

Table sugar

Milk

Starch

Cellulose

Bread, Pasta,

Cereals

Types of Lipid

Two of the main types of lipids are

Triglycerides

Phospholipids

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Triglyceride

It is made up of

3 fatty acid molecules

and

1 glycerol molecule

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This is the smallest lipid

Phospholipids

If one fatty acid of a lipid molecule is replaced by a phosphate group then a phospholipid is formed

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Sources of Lipids

• Fat – in and on meat

• Butter (80% fat)

• Cooking oils

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Learning check

The two main types of molecules that make up lipids are:

Fatty acids and Glycerol

The two main types of lipids are:

Triglycerides

Phospholipids

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Proteins

Proteins contain the elements Carbon HydrogenOxygen Nitrogen

Some may also contain sulphur, phosphorous or iron

Proteins are found in lean meat, fish, pulses, soya and eggs 30

Structure of Proteins

Proteins are made up of long chains of amino acids

Amino acids are joined together by peptide bonds

This results in the formation of polypeptide chains

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Learning check

Name the elements in proteins

Carbon Hydrogen

Oxygen Nitrogen

Sometimes they contain

sulphur, phosphorous or iron

Proteins are made up of long chains of

amino acids

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Need to know

• What is a vitamin?

• Name one water soluble vitamin.

• Name one water in-soluble vitamin (fat-soluble)

• List the sources of these vitamins

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Vitamins

Vitamins are complex organic chemicals that must be taken in the diet.

• Needed in small amounts, cannot be produced in the body

• Must be supplied continuously in diet and in sufficient quantities

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Vitamins

We need Vitamins A, B, C, D, E and K in our diets to keep us healthy

Vitamins can be water soluble or fat soluble

Vitamins B and C are water soluble

Vitamins A, D, E and K are fat soluble

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Sources of Vitamins

Vitamin Source

A Green leafy vegetables, Eggs, Cheese, Carrots

B Lean Meat, Cereals, Nuts

C Citrus Fruits, Green vegetables, Turnips

D Milk and Milk products, Sunlight

E Vegetable oils, fish, nuts

K Green leafy vegetables36

Learning check

What is a vitamin?

A vitamin is a complex organic chemical that must be taken in the diet.

What vitamins dissolve in water?

B & C

What vitamins are fat-soluble?

A, D, E and K37

Minerals

• Minerals are inorganic chemicals necessary in tiny amounts in the diet.

Plant Mineral Source Function Deficiency

Phosphate Soil Part of nucleic acids

Poor root growth

Magnesium Soil Part of chlorophyll

Lack of chlorophyll

Animal Minerals

Iron Liver, meat Part of haemoglobin

Low red blood cell count

Calcium Milk cheese Bones Weak bones

To Test for Reducing SugarsProcedure (pg 2 & 77)

1.Label test tubes A-F

2.Place 2cm glucose solution in test tube A

3.Place 2cm water (control) in test tube B

4.Place 2cm of each of the other foods in C-F

5.Add 2cm Benedicts Solution to each test tube.

6. Place test tubes in a water bath for 5-10min

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To test for Reducing Sugars pg. 2 & 77

7. Swirl the test tubes and note any colour change.

8. Record your results in the table.

Colour Change after heating test tube

Blue -> brick red means reducing sugar present

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To Test Food Samples for Starch pg. 4 & 78

Procedure

1.Label the wells in a spotting tile A-F

2.Add 1cm starch solution to well A

3.Add 1cm water (control) to well B

4.Add 1cm iodine solution to each well

5.Add 1cm other foods to well C-F and 1cm iodine solution

6.Record results in table42

To test foods for Starch

Colour Change

Iodine solution should turn blue/black in colour if starch is present in the food.

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To test a variety of foods for Fat

Procedure (pg 6 & 79)

1.Label six pieces of brown paper A-F

2.Place one drop of oil on A and leave to dry.

3.Place one drop of water on B and leave to dry.

4.Repeat steps 2 with other food samples

5.Record results when brown paper dries.44

To test a variety of foods for Fat

A translucent spot (see through spot) from the food sample will be visible on the dry brown paper if fat is present in the food

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To Test a variety of foods for Protein using Biuret Test

Procedure (pg 8 & 80)

1.Label spotting tile A-F

2.Place 1cm milk in well A

3.Add 1cm water (control) to well B

4.Add 1cm of Sodium hydroxide to well A and 2 drops of Copper sulphate.

5.Observe result

6.Repeat step 4-5 for other foods.46

To test a variety of foods for protein using the Biuret Test

The blue solution will turn purple/lilac if protein is present in the food.

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Results Table

Food Colour Change Presence/Absence

A.

B.

C.

D.

E.

F

G.

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