Transcript 1.3.1 Function of Food

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?
Energy
Growth 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 elements
C, 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
Zn
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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
Minerals
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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:
Carbohydrates
Lipids
Proteins
Vitamins
Carbohydrates
Carbohydrates contain the elements
Carbon
Hydrogen
Oxygen
The general formula for a carbohydrate is
Cx(H2O)y
Ratio Hydrogen:Oxygen
2
:
1
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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
Carbon
Hydrogen
Oxygen
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 sugars
C
soluble in water
sweet to taste
smallest carbohydrate unit
Examples:
Found in:
glucose, fructose
fruit
C
C
O
C
C
C
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Disaccharides
These are
• two monosaccharide 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 monosaccharide sugar molecules
joined together
• Not soluble in water
• Do not taste sweet
Example: starch, cellulose
Found 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:
Examples
Monosaccharides
Glucose
Sources
fruit
Fructose
Disaccharides
Polysaccharides
Sucrose
Table sugar
Lactose
Milk
Starch
Bread, Pasta,
Cellulose
Cereals
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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
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 (fatsoluble)
• 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 vegetables
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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 K
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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
Iron
Liver, meat
Part of
haemoglobin
Low red blood
cell count
Calcium
Milk cheese
Bones
Weak bones
Animal Minerals
To Test for Reducing Sugars
Procedure (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 540
10min
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 table
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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.
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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.
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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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