1.3.4 Biomolecular Sources and the Components of Food

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CarbohydratesCarbohydrates contain the elements

CarbonHydrogenOxygen

Usually in the ratio of 1C:2H:1OWritten as Cx(H2O)y

i.e. twice as many hydrogen atoms as oxygen atoms

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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

O

C C

C C

C

C

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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

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DisaccharidesThese are

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

• soluble in water

• sweet to taste

Examples: sucrose, lactose, maltose

Found in: table sugar, milk

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Polysaccharides

These are• Many single sugar molecules joined

together• Not soluble in water• Do not taste sweet

Example: starch, cellulose, glycogenFound in: bread, pasta, cereals

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Learning check

Name the three types of carbohydrate

• Monosaccharides

• Disaccharides

• Polysaccharides

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Learning check

Give examples and sources of:

Examples Sources

Monosaccharides

Disaccharides

Polysaccharides

Glucose

Fructosefruit

Sucrose

Lactose

Table sugar

Milk

Starch

Cellulose

Bread, Pasta,

Cereals

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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 LipidsThey 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 moleculesFatty acids and Glycerol

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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

This is the smallest lipid

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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

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Structure of ProteinsProteins are made up of long chains of

amino acidsThere are 20 common and several rare amino

acids found in proteinsMore 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

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Amino Acids

All amino acids contain four distinct chemical groups connected to a central carbon atom:

• an amino group • a single hydrogen atom • a carboxyl group

• a side chain

The “acid “

part

Do NOT need this for exam

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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 vegetables

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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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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.

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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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END