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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
36
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
39
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
40
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
45
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.
47
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.
52
Energy Transfer Reactions
Respiration – Catabolic reaction
C6H12O6 + Oxygen Energy + CO2 + H2O release
Photosynthesis – Anabolic reaction
CO2 + H2O + Energy C6H12O6 + Oxygen absorbed
53
Learning check
Is anabolism the opposite of catabolism ?
No
Why?
Different chemical pathways involved in both.
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