Transcript KS3 Biology - Science at St. Dominics

Biology
Food
Objectives for food
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State the Function of Food
Name three reasons for requiring food
Name six common chemical elements in food: C, H, N, O, P, S
Name five elements present in dissolved salts: Na, Mg, Cl, K, Ca
Name 3 trace elements required: Fe, Cu, Zn
Define Biomolecular Structures
State that simple biomolecular units are composed of a combination of elements in different ratios. Eg
carbohydrates Cx(H2O)y
Name the element components, biomolecular components and sources of: carbohydrates, fats & oil and
proteins.
State that carbohydrates are composed of indivisible units and give examples of these. Eg. Monosaccharide –
glucose; Disaccharides – maltose; and Polysaccharides - starch/cellulose.
State that carbohydrates & lipids act as a primary source of energy.
State carbohydrates role as cellulose in cell walls
State that proteins act as enzymes and are made of amino acids
State proteins role as fibrous protein e.g. keratin or as myosin
State that hormones (protein) act as regulators of metabolic activity.
State the role of lipids as Phospholipids in cell membranes
State the requirements & use of any 2 minerals in plants.
State the requirements & use of any 2 minerals in animals.
Explain what a vitamin is.
Name one water-soluble vitamin. Name one water in-soluble (fat-soluble) vitamin.
List the sources of these vitamins
State that vitamin C & D are used for tissue growth, cell production and health maintenance.
Name disorders associated with deficiency of a water-soluble and a water in-soluble vitamin.
State 5 good reasons why water is important for organisms.
Define of the terms: Anabolic and Catabolic.
Give an example of each
Food is needed for:
1.Energy
2.Growth of new cells and
Repair of existing cells, tissues, organs,
etc.
3. Provides materials needed for metabolism
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
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
Test yourself…
• What are three functions of food?
• There are six elements present in food.
Can you name them?
• What elements are present in salts found
in our bodies?
• Name 3 trace elements.
By the end of today’s class you
should be able to…
• Define Biomolecular Structures
• State that simple biomolecular units are
composed of a combination of elements in
different ratios. Eg carbohydrates Cx(H2O)y
• Name the element components, biomolecular
components and sources of: carbohydrates,
• State that carbohydrates are composed of
indivisible units and give examples of these.
• Do a test for the presence of reducing sugar in
food.
Types of Food
Food is made up of six different food groups
Water
Proteins
Lipids
Carbohydrates
Vitamins
Minerals
Humans need to consume a balanced
diet which contains all of the nutrients
in different amounts for the needs of the
body
The main nutrients the body needs are:
 carbohydrates for energy;
 proteins for growth and repair;
 fats to store energy;
 vitamins and minerals to keep the body healthy.
Which food type does the body need the most of?
What is a balanced diet?
Nutrients in food
Learning check
What are the six different food components?
Water
Proteins
Lipids
Carbohydrates
Vitamins
Minerals
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
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
Another common carbohydrate
General formula = Cx(H2O)y
When x = 12 and y = 11
We fet the formula C12H22O11
What is the name of this disaccharide
carbohydrate?
Sucrose
Learning check
Name the three elements that make up
carbohydrates
Carbon
Hydrogen
Oxygen
What is the general formula for a carbohydrate?
Cx(H2O)y
Carbohydrates which are made of long chains of identical
small sugar molecules.
carbohydrate
molecule
one sugar
molecule
The long chains of carbohydrates are broken down into the
smaller sugar molecules
These are used by the body to release
energy
3 Types of Carbohydrate
Monosaccharides
Disaccharides
Polysaccharides
Monosaccharides
These are
single sugar molecules
smallest carbohydrate unit
Examples:
Found in:
glucose, fructose
fruit
Disaccharides
These are
• two monosaccharide sugar units joined
together – known as double sugar molecules
Examples:
Found in:
sucrose, lactose, maltose
table sugar, milk
Polysaccharides
These are
• Many sugar molecules joined together
Example: starch, cellulose
Found in: bread, pasta, cereals
Learning check
Name the three types of carbohydrate
• Monosaccharides
• Disaccharides
• Polysaccharides
To test for the presence of a
reducing sugar
• Stand the two test
tubes in boiling water
for about 3 minutes.
• If sugar is present in
a food it will turn
Benedict's solution
from blue to red
How can you test different foods for
the presence of a simple sugar..
• It has to be a fair test
• There has to be a control experiment – a
standard to compare the other
experiments against.
Can you..
• Name the elements present in carbohydrates?
• Know the ratio which describes carbohydrates?
• Know the ratio of oxygen to hydrogen in
carbohydrates?
• Know the three types of carbohydrates and give
examples of them?
• Describe how to do a test for the presence of
reducing sugar in food.
To test for the presence of starch
• Iodine turns from yellow/brown to
blue/black if starch is present
Learning check
Give examples and sources of:
Examples
Glucose
Monosaccharide
Fructose
s
Disaccharides
Sources
fruit
Sucrose
Table sugar
Lactose
Milk
Starch
Bread, Pasta,
Polysaccharides Cellulose
Cereals
The‘Structural Role of Carbohydrates
The function/job of carbohydrates in making
parts of living things
Cellulose
(polysaccharide) found
in plant cell walls
• Chitin (polysaccharide)
found in insect
exoskeletons
The Metabolic Role of
Carbohydrates
the function of carbohydrates in the
chemical reactions in cells
These are the primary sources of energy
for metabolism – e.g.
• glucose (carbohydrate) is an immediate
source of energy
• What a lipid is
• The structure of triglycerides and
phospholipids
• How to test for fats
• Some sources of fat in our diet.
Lipids
Are:
• 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.
Structure of Lipids
They are made up of the elements
carbon
hydrogen
oxygen
But dont have the same ratios as
carbohydrates.
What are fats?
fat
molecule
glycerol
Lipids are made up of fatty acids and glycerols
fatty
acids
Triglyceride
This is the smallest lipid
It is made up of
3 fatty acid molecules
and
1 glycerol molecule
Phospholipids
If one fatty acid of a lipid molecule is
replaced by a phosphate group then a
phospholipid is formed
A special test for the presence of
lipids
Lipids make brown
paper go translucent
(light passes through it
very easily)
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Sources of Lipids
Fat – in and on meat
Butter (80% fat)
Cooking oils
Structural role of Lipids
• Heat insulation – e.g. under the skin
• Protection around body organs e.g. kidney,
heart
• Phospholipids and lipoproteins are major
parts in cell membranes
Metabolic Role of Lipids
These are the primary sources of energy
for metabolism – e.g.
• lipids are a long-term energy storage
• What a lipid is
• The structure of triglycerides and
phospholipids
• How to test for fats
• Some sources of fat in our diet.
• The role of fats in our diet
• What a protein is
• How to test for proteins
• Some sources of protein in our diet.
Proteins
Proteins contain the elements
Carbon
Hydrogen
Oxygen
Nitrogen
Some may also contain sulphur,
phosphorous or iron
What are proteins?
protein
molecule
one
amino
acid
Proteins are made up of chains of small molecules called
amino acids. There are over 20 different kinds of amino acid.
•Amino acids are joined together by peptide bonds
•This results in the formation of polypeptide chains
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
To test for the presence of protein in food:
Dissolve the food in some
water.
Add 2cm3 of BIURET
SOLUTION
If protein is present the
solution will turn from a
blue to a purple colour!
Sources of protein
Milk
Nuts
Eggs
Cheese
Meat
Structural role of
Proteins
• Proteins combine with
phospholipids to from cell
membranes
• Keratin is the structural
protein in skin, hair and
nails
• Myosin is the structural
protein in muscle
Metabolic Role of Proteins
• Enzymes ( made of protein) control the
rate of chemical reactions in cells.
• Chlorophyll is a protein that traps the
sun’s energy during photosynthesis
Metabolism
(all of the chemical reactions in a living thing)
Anabolic reactions
Small molecules are combined
to make larger molecules.
Energy is needed
Catabolic reactions
Large molecules are broken
down into smaller molecules.
Energy is given out.
• Respiration
Glucose is burnt with
oxygen in the body
to make energy.
Carbon dioxide and
water are also
made.
• Photosynthesis
Carbon dioxide and
water taken in by a
plant. Light is
needed. The plant
makes glucose.
Metabolic Role of Hormones
Hormones are made of lipids or protein
Hormones regulate body functions
e.g. the hormone insulin controls the amount
of glucose in the blood
Metabolic Role of Vitamins
Definition: Vitamins are organic substances
needed in small amounts for the metabolism
to function normally
Class activity
• Make up your own fact sheet on Vitamin C and
Vitamin D
• Do these on PowerPoint slides. One for each
Vitamin. Then save the file with your name and
send it on.
You should have:
• Sources, functions, is it water soluble, and one
deficiency disease. Use pictures if you can when
finished!!!
Vitamin C
Solubility:
water soluble
Function: for building connective
tissue i.e. tissue used for attaching
organs together
Source:
Fruit
Scurvy – not enough vitamin C
Loose teeth, bleeding
gums
Vitamin D – Fat soluble
Needed to absorb
calcium from the
blood which builds
strong bones and
teeth
Source:
Milk, cheese, yogurt,sunlight
Rickets in children – not
enough vitamin D
Softened
bones or
bow legs
Need to know
• Describe what an anabolic and a catabolic reactions
are and give examples
• State the metabolic role of fats
• State the metabolic role of carbohydrates
• State the metabolic role of proteins
• State the metabolic role of hormones
• Define vitamin
• State the functions and sources of vitamin C & D
• Name disorders associated with deficiency of a water
soluble and a fat-soluble vitamin
Water (H20)
1. It is a solvent for transporting substances in
blood or in plants
2. It is where chemical reactions take place in
cells
3. It is a reactant/product in chemical reactions
4. Controls cell shape.
• It is slow to heat up and cool down – kept at a
fairly steady temperature – helps to keep a
constant rate of metabolism.
Minerals
Minerals are salts formed from the earth’s
rocks.
The salts then dissolve in water and are
absorbed by plants.
Animals then eat the plants.
Minerals and Plants
They use:
• Calcium (Ca) to make cell walls
• Magnesium (Mg) to make the pigment
chlorophyll
Minerals and Animals
They use
• Calcium (Ca) to make bones and teeth
• Iron (Fe) to make the pigment
haemoglobin