1.3.4 Biomolecular Sources and
the Components of Food
Carbohydrates
Carbohydrates contain the elements
Carbon
Hydrogen
Oxygen
Usually in the ratio of 1C:2H:1O
Written 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 sugars
soluble in water
sweet to taste
smallest carbohydrate unit
Examples:
Found in:
C
C
O
C
glucose, fructose
fruit
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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Disaccharides
These are
• two single sugar units joined together – known as
double sugar molecules
• soluble in water
• sweet to taste
Examples:
Found in:
sucrose, lactose, maltose
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, glycogen
Found 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
Monosaccharides
Glucose
Sources
fruit
Fructose
Disaccharides
Polysaccharides
Sucrose
Table sugar
Lactose
Milk
Starch
Bread, Pasta,
Cellulose
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 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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Types of Lipid
Two of the main types of lipids are
Triglycerides
Phospholipids
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Triglyceride
This is the smallest lipid
It is made up of
3 fatty acid molecules
and
1 glycerol molecule
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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
Hydrogen
Oxygen
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 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
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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 (fatsoluble)
• List the sources of these vitamins
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END
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