1.3.1 Function of Food

Why do we need food?

Need to know

• The Function of Food • Three reasons for requiring food

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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:

1. Metabolism and

2. Continuity

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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

Need to know

• Chemical elements• Six common elements in food• Five elements in dissolved salts• Three trace elements

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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

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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 Zn9

1.3.3 Biomolecular Structures1.3.3 Biomolecular Structures

Need to know

• Define Biomolecular Structures • State that simple biomolecular units are

composed of a combination of elements in different ratios e.g. carbohydrates Cx(H2O)y

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Types of Food

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

Food is made up of six different components

Water Proteins

Lipids Carbohydrates

Vitamins Minerals 12

Humans are mainly made up of Water!

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Carbohydrates

Carbohydrates contain the elements

Carbon Hydrogen Oxygen

The general formula for a carbohydrate is

Cx(H2O)y

There are twice as many hydrogen molecules as oxygen molecules

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Learning check

What are the six different food components?

Water Proteins

Lipids Carbohydrates

Vitamins Minerals

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A common carbohydrate

General formula = Cx(H2O)y

When x = y = 6

We fet the formula C6H12O6

What is the name of this monosaccharide carbohydrate?

Glucose

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Another common carbohydrate

General formula = Cx(H2O)y

When x = 12 and y = 11

We get the formula C12H22O11

What is the name of this disaccharide carbohydrate?

Sucrose

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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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1.3.4 Biomolecular Sources and the Components of Food

Need to know

• State that simple bio molecular units are composed of a combination of elements in different ratios e.g. carbohydrates Cx(H2O)y

• Name the element components, bio molecular components and sources of: carbohydrates, lipids and proteins.

• State that carbohydrates are composed of indivisible units and give examples of these e.g. – Monosaccharides – glucose; – Disaccharides – maltose; & – Polysaccharides – starch/cellulose. 20

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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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 24

Photo Credit fruit image by Edvin selimovic from Fotolia.com

Learning check

What are the elements that make up all carbohydrates?

Carbon Hydrogen Oxygen

Can you remember the general formula for a carbohydrate?

Cx(H2O)y 25

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, milk26

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.)

• steroids which include cholesterol and some of the sex hormones

• waxes which cover insect bodies and plant leaves.

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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 30

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 lipidFatty Acid 1

Fatty Acid 2

Fatty Acid 3

Glycerol

Phospholipids

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

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Fatty Acid 1

Fatty Acid 2

Glycerol

Phosphate

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 37

Structure of Proteins

Proteins are made up of long chains of amino acids

There are 20 common and several rare amino acids found in proteins

More amino acids are found in cells and tissues but are not in proteins

Amino acids are joined together by peptide bonds

This results in the formation of polypeptide chains 38

Learning check

Proteins contain the elements

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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Vitamins

Vitamins are essential organic catalysts of metabolism

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

• Must be supplied continuously and in sufficient quantities

• Differ from each other chemically

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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 vegetables42

Learning check

What is a vitamin?

A vitamin is an essential organic catalyst of metabolism

What vitamins dissolve in water?

B & C

What vitamins are fat-soluble?

A, D, E and K

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1.3.5 Energy Transfer Reactions

Anabolic & Catabolic

Or

Anabolism & Catabolism

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Need to know

Definition of the terms:

Anabolic

Catabolic

Give an example of each

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Anabolic Reactions

This is where energy is used to make large molecules (e.g. C6H12O6) from smaller ones (e.g. CO2 and H2O) using enzymes

e.g. Photosynthesis – glucose molecules are formed from carbon dioxide and water using enzymes and the energy from the sun.

This is anabolism. Energy is absorbed.

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An Anabolic Reaction

Energy being used to join two small molecules to make a larger molecule

ENERGYSmall molecule Small molecule

Larger molecule

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Catabolic Reactions

This is where energy is released when large molecules (e.g. C6H12O6) are broken down to form smaller ones (e.g. CO2 and H2O) using enzymes

e.g. Respiration – glucose molecules are broken down by enzymes to form carbon dioxide and water and energy is released.

This is catabolism. Energy is released.

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Learning check

Explain AnabolismEnergy absorbed. Small large molecules

Give an example of an anabolic reactionPhotosynthesis

Explain CatabolismEnergy released. Large small molecules

Give an example of a catabolic reactionRespiration

CRAPCatabolic Respiration Anabolic Photosynthesis

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Is catabolism the opposite of anabolism? – NO

In the examples just given the chemical processes (pathways*) involved in each of them are different, therefore catabolism is not the opposite of anabolism.

* e.g. if you travel from A to B – you followed a certain pathway. On the return journey you may come home through C – you followed a different pathway.

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Energy Transfer Reactions

Respiration – Catabolic reaction

C6H12O6 + Oxygen Energy + CO2 + H2O release

Photosynthesis – Anabolic reaction

CO2 + H2O + Energy C6H12O6 + Oxygen absorbed

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Learning check

Is anabolism the opposite of catabolism ?

No

Why?

Different chemical pathways involved in both.