Transcript 1.3.1 Function of Food

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?
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
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 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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1.3.3 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
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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.
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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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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
soluble in water
sweet to taste
smallest carbohydrate unit
Photo Credit fruit image by Edvin selimovic
from Fotolia.com
Examples:
Found in:
glucose, fructose
fruit
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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 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.)
• 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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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
3 fatty acid molecules
and
1 glycerol molecule
Glycerol
It is made up of
Fatty Acid 1
Fatty Acid 2
Fatty Acid 3
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Phospholipids
If one fatty acid of a lipid molecule is
replaced by a phosphate group then a
phospholipid is formed
Fatty Acid 1
Glycerol
Phosphate
Fatty Acid 2
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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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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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1.3.5 Energy Transfer
Reactions
Anabolic & Catabolic
Or
Anabolism & Catabolism
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
Small molecule
Small molecule
ENERGY
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 Anabolism
Energy absorbed. Small  large molecules
Give an example of an anabolic reaction
Photosynthesis
Explain Catabolism
Energy released. Large  small molecules
Give an example of a catabolic reaction
Respiration
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CRAP
Catabolic 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.
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