The document provides information on biological molecules including proteins, carbohydrates, lipids, and nucleic acids. It describes the structures of these molecules including their monomers, polymers, and interactions. It also explains how their structures relate to their functions in living organisms. Enzymes are discussed as globular proteins that catalyze reactions. The mechanisms of enzyme action and how environmental factors like temperature, pH, and concentration affect enzyme activity are described. DNA and RNA structures are outlined along with their roles in protein synthesis and replication.

1. Emily Summers
AS Unit F212: Molecules, biodiversity, food and health
Module 1 - Biological molecules
Biological molecules
Describe how hydrogen bonding occurs between water molecules, and relate this and other properties of water to the roles of water
in living organisms.
Describe, with the aid of diagrams, the structure of an amino acid.
Structure of an Amino Acid
All amino acids have the same
general structure, a carboxyl group,
an amino group attached to a carbon
atom (-NH2) but the R group is
variable, and that is the only
difference between amino acids.
Structure of Glycine
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2. Emily Summers
Describe, with the aid of diagrams, the formation and breakage of peptide bonds in the synthesis and hydrolysis of dipeptides and
polypeptides.
Condensation reactions make
peptide bonds between amino acids.
A molecule of water is released.
It’s reversible, and by adding a water
molecule you can break the peptide
bonds. This is called hydrolysis.
Explain, with the aid of diagrams, the term primary structure.
Explain, with the aid of diagrams, the term secondary structure
with reference to hydrogen bonding.
Explain, with the aid of diagrams, the term tertiary structure, with
reference to hydrophobic and hydrophilic interactions, disulphide
bonds and ionic interactions
Ionic Interactions weak attractions
between oppositely charged parts the
molecule
Disulfide Bonds  Two molecules of an
amino acid close together, the sulphur
atoms in them bond together forming this
bond. (E.g. Cysteine)
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3. Emily Summers
Hydrophobic Water repelling groups near together in a protein they clump.
Hydrophilic Water attracting groups are likely to be pushed outside, affecting the
protein’s final structure.
Explain, with the aid of diagrams, the term quaternary structure, with reference
to the structure of haemoglobin.
The quaternary structure tends to be determined by
the tertiary, when it involves multiple polypeptides.
E.g. Haemoglobin has a quaternary structure, it has
4 polypeptide chains.
Describe, with the aid of diagrams, the structure of a collagen molecule
Collagen is a strong protein that is fibrous. It is a
supportive tissue in animals; it is made of three
polypeptide chains that are very tightly coiled into a
triple helix, interlinked by covalent bonds. Minerals
are able to bind to this helix to increase rigidity.
Tendons are made up mostly of collagen
Walls of arteries contain collagen to prevent
bursting from high pressure blood in them
Cosmetic treatment for lips for a fuller appearance
Compare the structure and function of haemoglobin (as an example of a globular protein) and collagen (as an example of a fibrous
protein).
Haemoglobin Collagen
Globular protein Fibrous Protein
Large variety of amino acids in it’s primary 35% of primary structure is glycine
structure
Has a prosthetic group- haem Doesn’t contain a prosthetic group
Mostly wound into alpha helix structures Mostly left handed helix structures
Describe, with the aid of diagrams, the molecular structure of alpha-glucose as an example of a monosaccharide carbohydrate.
Monosaccharide carbohydrate, a hexose
sugar because it has six carbon atoms in
every molecule. The structure determines its
solubility so it can be easily transported. It’s
a source of energy for animals and plants.
Its chemical bonds have lots of energy in
them.
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4. Emily Summers
State the structural difference between alpha- and beta-glucose.
Describe, with the aid of diagrams, the formation and breakage of glycosidic bonds in the synthesis and hydrolysis of a disaccharide
(maltose) and a polysaccharide (amylose).
Condensation- H2O removed!
Hydrolysis- H2O breaks glycosidic
bond.
Compare and contrast the structure and functions of starch (amylose) and cellulose .
Starch Cellulose
Large molecules of many alpha glucose Large molecules of many beta glucose
molecules joined with condensation molecules joined with condensation
reactions, insoluble in water and form reactions, they are insoluble in water and
granules also strong
For energy storage in plants Structural found in plants where it forms
cell walls
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5. Emily Summers
Describe, with the aid of diagrams, the structure of glycogen.
Excess glucose is stored as glycogen
in animals.
The 1-4 and 1-6 glycosidic bonds
cause branching!
Meaning that the glucose can be
quickly released- good for animals!
Explain how the structures of glucose, starch (amylose), and glycogen and cellulose molecules relate to their functions in living
organisms.
Carbohydrate Example Characteristics Function in
Organisms
Monosaccharide Glucose (6 Carbon Small, soluble, sweet, Energy via respiration
monomers sugar) crystalline
Deoxyribose (5 Part of DNA
Carbon sugar) information molecule
Disaccharide dimers Maltose (2 glucoses) Small, soluble, sweet Sugar obtained when
& crystalline starch is broken down
in hydrolysis, can be
split to glucose for
more respiration
Polysaccharide Starch & glycogen Large molecules, Energy store in plants
polymers many alpha glucose as cellulose and
molecules joined by glycogen in animals
condensation. and fungi
Insoluble in H2O and
form granules
Cellulose Large molecules of Structural in plants for
many beta glucose cell walls.
molecules joined by
condensation.
Insoluble in H2O and
are strong.
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6. Emily Summers
Compare, with the aid of diagrams, the structure of a triglyceride and a phospholipid.
Phospholipid
Phospholipids are similar to
triglycerides except that one of
Triglyceride
the fatty acid molecules is
replaced by a phosphate group.
Fatty acid tails are hydrophobic
Phosphate group is hydrophilic
and faces outwards. Good in the
bilayer for cell membranes so
water soluble substances find it
hard to get through.
Explain how the structures of triglyceride, phospholipid and cholesterol molecules relate to their functions in living organisms.
Triglyceride molecules are used as energy storage molecules. This is good because the
hydrocarbon tails of the fatty acids have lots of chemical energy that is released when
broken down, so lipids contain double the energy carbohydrates do.
They are insoluble because of their hydrophobic so they do not interfere with the water
potential in cells that would cause water to enter cells by osmosis so they could
swell/burst.
Phospholipid molecules have a hydrophilic head and a hydrophobic tail. The head faces
outwards and the tail faces inwards in the phospholipid bilayer on cell surface
membranes, making it difficult for water soluble substances like Na+ ions and glucose to
pass through.
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7. Emily Summers
Cholesterol is a lipid found in cell membranes for mechanical stability, and is used to
make steroids. It has a hydrocarbon ring structure attached to a hydrocarbon tail. The
hydrocarbon ring has a polar hydroxyl group attached to it which makes it soluble.
Describe how to carry out chemical tests to identify the presence of the following molecules: protein (biuret test), reducing and non-
reducing sugars (Benedict’s test), starch (iodine solution), and lipids (emulsion test).
Biuret’s Test
Add Benedict’s solution to the substance and heat to 80 degrees Celsius in a water
bath. If the solution changes colour from blue to green-brick red then it is a reducing
sugar. (Monosaccharide and disaccharide)
Non reducing sugars do not react with Benedict’s solution so there would be no colour
change E.g. Sucrose, formed by a condensation reaction between glucose and
fructose. The formation of this bond is different to reducing sugars, so it must be boiled
with hydrochloric acid, to hydrolyse/split the sucrose molecules to give glucose and
fructose monosaccharides. Then add an alkali to a cool solution to neutralise it, e.g.
NaCO3 solution. Then do the reducing sugar test and you should get a positive result.
Starch
Add iodine in a potassium iodide solution to the sample, and if there is starch the
sample solution will change from yellow/brown to a dark blue/black. Negative results
present no colour change.
Lipids
Mix the sample with ethanol, dissolving lipids present. Pour the solution into water in a
separate test tube. If there is a lipid there will be a cloudy white milky emulsion near the
top of the water.
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8. Emily Summers
Protein
Add biuret reagent to a sample. The reagent contains sodium hydroxide and copper
sulphate, reacting with the peptide bonds in protein turning the solution to a purple
colour if there is protein, and staying blue if there is no protein.
Describe how the concentration of glucose in a solution may be determined using colorimetry.
A colourimeter measures the absorbance of light of a solution; the more concentrated
the colour the higher the absorbance is.
Make up several glucose solutions of known, different solutions
Do a Benedict’s test on each solution, same amount in each case make sure
there is excess reagent
Remove precipitate (Centrifuge/ leave for a day)
Use colourimeter to measure absorbance of Benedict’s solution remaining in
each tube
Record your results in a calibration curve (absorbance against glucose
concentration)
Test the unknown solution by using the colourimeter and reading it’s absorbance
value across on the calibration graph, it will tell you the concentration.
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9. Emily Summers
Nucleic Acids
State that deoxyribonucleic acid (DNA) is a polynucleotide, usually double-stranded, made up of nucleotides containing the bases
adenine (A), thymine (T), cytosine (C) and guanine (G).
A nucleotide
A phosphate group
Adenine and Thymine bond together with 2
hydrogen bonds, Cytosine and guanine join with
3 hydrogen bonds
Deoxyribose
Joined with covalent bonds (sharing of electrons)
State that ribonucleic acid (RNA) is a polynucleotide, usually single-stranded, made up of
nucleotides containing the bases adenine (A), uracil (U), cytosine (C) and guanine (G).
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10. Emily Summers
Describe, with the aid of diagrams, how hydrogen bonding between complementary base pairs (A-T, G-C) on two anti-parallel DNA
polynucleotides leads to the formation of a DNA molecule, and how the twisting of DNA produces its double-helix shape.
Outline, with the aid of diagrams, how DNA replicates semi-conservatively, with reference to the role of DNA polymerase.
The enzyme called DNA helicase breaks the hydrogen bonds between the two
polynucleotide DNA strands unzipping the helix to form two single strands,
exposing the bases.
Each original strand is a template for a new strand, free floating DNA nucleotides
join to exposed bases on each original template strand by complementary base
paring (purine pyrimidine, A- -T, G- - -C)
The nucleotides on the new strand are joined by DNA polymerase, and new
hydrogen bonds are formed between the bases on the old and new strand.
Each DNA molecule contains one strand from the original DNA molecule and one
new strand.
State that a gene is a sequence of DNA nucleotides that codes for a polypeptide.
Gene  A gene is a length of DNA that carries the code for the synthesis of one or
more specific polypeptides.
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11. Emily Summers
Outline the roles of DNA and RNA in living organisms (the concept of protein synthesis must be considered in outline only).
The sequence of bases on DNA are code instructions for proteins, they code for the
amino acid sequence present in the protein. This is a gene.
There are three forms of RNA:
Messenger RNA  Is a strand complementary to a strand of a DNA molecule, a
template strand that is a copy of the coding strand of the double helix
Ribosomal RNA  In ribosomes
Transfer RNA  Carries amino acids to the ribosomes and they are bonded together to
form polypeptides.
Enzymes
State that enzymes are globular proteins, with a specific tertiary structure, which catalyse metabolic reactions in living organisms.
Enzymes are:
Globular proteins and soluble in water
Able to break molecules down or build them up!
Biological catalysts
Specific- because they catalyse a reaction with only one type of substrate
Their globular structure has a pocket called an active site
Activity affected by temperature and pH (Rate of reaction)
Enzymes are large molecules with hundreds of amino acids. A lot of these amino acids
work to keep the specific tertiary structure of the enzyme. The function of the enzyme
depends on the shape, and for the enzyme to work correctly the tertiary structure must
be maintained specifically.
All of the structures (primary, secondary, tertiary) of the enzyme is involved in the
specific active site shape. (Where the catalytic activity of the enzyme happens)
Enzymes are faster than catalysts and because they are specific to one reaction they do
not produce unwanted by products.
An individual cell could contain over one thousand enzymes to catalyse every process,
like digestion, respiration, photosynthesis.
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12. Emily Summers
State that enzyme action may be intracellular or extracellular.
Extracellular Enzymes catalase reactions outside of the cell
Intracellular Enzymes catalase reactions inside of the cell
Mould produces extracellular enzymes to digest bread.
Phagocytes take in and digest bacteria using lysosomal enzymes.
Describe, with the aid of diagrams, the mechanism of action of enzyme molecules, with reference to specificity, active site, lock-and-
key hypothesis, induced-fit hypothesis, enzyme-substrate complex, enzyme-product complex and lowering of activation energy.
Enzymes reduce the amount of activation energy needed, so reactions happen quickly
at lower temperatures, because of the way the active site is shaped to fit the substrate.
Enzyme’s active site is complementary to the shape of the substrate, they are specific.
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13. Emily Summers
Describe and explain the effects of pH, temperature, enzyme concentration and substrate concentration on enzyme activity.
pH
pH is the measure of the H+ ion concentration. These ions are positive so they are
attracted to negatively charged ions, or parts of molecules and repelled by positive
parts. Hydrogen bonds and ionic bonds hold the tertiary structure of an enzyme in place
so the active site is maintained in it’s correct shape. The bonds are there because of
electrostatic attraction between opposite charges on the amino acids making up the
enzyme.
Hydrogen ions interfere with these bonds and can alter the tertiary structure of an
enzyme by altering their concentration.
Enzymes have their own optimum pH, the H+ ion concentration gives the enzyme the
best overall shape. Enzymes work in a narrow pH range usually, and their pH range
often changes with their location. E.g. Pepsin is in the stomach and has an optimum pH
of 2. Handy! Whereas Trypsin has an optimum pH of 7 which is good for the conditions
of the small intestine it works in, where it digests protein.
Temperature
When you apply heat to molecules, they
move faster in a liquid or gas and they also vibrate.
The vibrations strain the bonds holding the
molecules.
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14. Emily Summers
In large molecules like enzymes the vibration of molecules can break weaker bonds like
hydrogen or ionic bonds.
The weaker bonds are there in abundance in an enzyme molecule and hold the tertiary
structure in place, so they maintain the active site’s correct, specific shape.
Increasing temperature = Increasing bonds broken
And the tertiary structure is held less in the shape of the active site needed for it to work.
So rate of reaction will decrease if the substrate can’t fit in the active site.
If enough of the bonds are broken, the entire tertiary structure unravels and the
enzyme stops working.
If the tertiary structure of an enzyme is changed enough it will not function and it is not
restorable  denaturation.
Denaturation Changes only the tertiary structure of an enzyme so it can’t
function and its function can’t be restored, which changes the active site of the
enzyme.
Concentration
Increasing the enzyme concentration increases rate of reaction to a point, until it will not
increase anymore because substrate concentration is the limiting factor. Reactions
cannot be quick if there isn’t enough substrate left, and vice versa.
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15. Emily Summers
Describe how the effects of pH, temperature, enzyme concentration and substrate concentration on enzyme activity can be
investigated experimentally.
Variable Method of Keeping Reasons
Constant
Temperature Carrying out the enzyme Room temperature changes
controlled reaction in a and fluctuations in the
water bath with thermostat temperature alters the
enzyme controlled reaction
so results will not reflect the
true action of the
independent variable that is
being found
Enzyme Concentration Use an accurate measured Rate of reaction depends
volume of enzyme-solution on concentration of enzyme
molecules present; using
accurate volumes of
enzyme solution gives a
true constant conc. Of
enzyme molecules
Living tissue Mass of Assume that the pieces of
tissue has to be accurate tissue have the same
number of enzyme
molecules
Whole pieces of tissue The number of enzymes
same surface area and that have contact with
mass substrate affects rate of
reaction, e.g. surface area
Substrate Concentration Accurately measured Rate of reaction depends
substrate volume/mass on substrate molecule
concentration
pH value Use pH buffers by keeping Rate of reaction depends
H+ concentration constant on pH because it alters the
shape of the active site of
the enzyme
Explain the effects of competitive and non-competitive inhibitors on the rate of enzyme-controlled reactions, with reference to both
reversible and non-reversible inhibitors.
Competitive inhibitors have a similar shape to the substrate so they occupy the active
site and form an enzyme inhibitor complex but no product is made. So the enzyme
cannot catalyse a reaction and rate of reaction slows down. Depends on inhibitor and
substrate concentration, e.g. if you increase substrate rate of reaction may increase.
Non Competitive inhibitors don’t occupy the active site, but attach somewhere else on
the enzyme to distort the tertiary structure of the enzyme. So the active site changes
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16. Emily Summers
and the substrate can’t fit anymore, so no reaction can be catalysed and reaction rate
decreases. Increasing substrate concentration has no effect.
Reversible inhibitors are when the inhibitor isn’t there permanently and afterwards the
enzyme is unaffected.
Non Reversible inhibitors are usually non competitive and the enzyme is denatured.
Explain the importance of cofactors and coenzymes in enzyme-controlled reactions
Coenzymes take part in the reaction and are changed, but are recycled back to take
place in the next reaction.
Cofactors are there to ensure an enzyme controlled reaction takes place at an
appropriate rate, and some enzymes can only catalyse a reaction if a cofactor is there.
State that metabolic poisons may be enzyme inhibitors, and describe the action of one named inhibitor.
Lots of poisonous substances have their effects due to inhibiting or over-activating
enzymes. For instance, Potassium Cyanide inhibits respiration of cells, because it is a
non competitive inhibitor for a vital respiratory enzyme, cytochrome oxidase, in the
mitochondria. When cytochrome oxidase is inhibited the use of oxygen is reduced
and ATP cannot be produced. So the organism is only able to respire anaerobically,
which builds up lactic acid in the blood increasing its acidity.
State that some medicinal drugs work by inhibiting the activity of enzymes.
Viral infections are treated using chemicals that act as protease inhibitors, which stop
viruses from replicating by inhibiting the activity of protease- which are vital to viruses to
build their new virus coats. Usually these inhibitors are competitive.
Cystic Fibrosis sufferers have the problem that the passage of digestive enzymes that
are usually secreted from the pancreas into the gut is blocked, leading to digestive
problems. Enzymes in a tablet can overcome the problem; they are in an acid
resistant coat so they’re not destructed by acid/protein digesting enzymes located in
the stomach.
Module 2 Food and Health
Diet and Food Production
Define the term “Balanced Diet”
A diet that contains all the nutrients needed for health in appropriate portions
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17. Emily Summers
Explain how consumption of an unbalanced diet can lead to malnutrition, with reference to obesity.
Malnutrition is caused by an unbalanced diet, which includes obesity- having a BMI of
30 or over, with 20% or more above the recommended weight for your height, If you
consume too little or too much of each food group.
BMI = mass in kg/ height in m2
Discuss the possible links between diet and coronary heart disease (CHD).
There are many health risks linked to an unbalanced diet and obesity. E.g. cancer,
cardiovascular disease and type two diabetes.
CHD is the result of fatty depositions in the walls of the coronary arteries.
(Atherosclerosis)
Salt decreases blood water potential so more water is in the blood and BP +, causing
hypertension, which is a too high blood pressure especially at diastolic pressure when
the heart should be relaxing with a lower BP. This can damage the arteries inner lining
which can help to cause atherosclerosis.
Lipids Animal fat is usually saturated and plant fat is usually unsaturated. Saturated =
BAD! Monounsaturated & Polyunsaturated= GOOD!
Cholesterol has similar properties to triglycerides. In meat, eggs, dairy. Concentration
of cholesterol in blood shouldn’t exceed 5.2 mmol dm-3
Discuss the possible effects of a high blood cholesterol level on the heart and circulatory system, with reference to high density
lipoproteins (HDL) and low density lipoproteins (LDL).
HDL’s are made by unsaturated fats, cholesterol and protein. They carry cholesterol
from the body tissues to the liver usually. The cells in the liver have receptor sites that
let the HDL’s bind onto their cell surface membranes. In the liver the cholesterol is used
in cell metabolism to make bile or it can be broken down so high levels of HDL’s are
linked with reducing blood cholesterol levels.
This is because they decrease fatty deposition in the artery walls caused by
atherosclerosis and can even help to remove depositions of it. HDL’s use unsaturated
fats, which are thought to be more beneficial to health than saturated fats.
LDL’s/Low density Lipoproteins are made by a combination of saturated fats,
cholesterol and protein. They usually carry cholesterol from the liver to the tissues.
The tissue cells contain receptor sites that let the LDL’s bind to their cell surface
membranes.
If there is too much saturated fat and cholesterol is consumed in the person’s diet then
the blood concentration of low density lipoproteins will increase.
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18. Emily Summers
Different fats will affect the low density lipoprotein receptors in different ways.
For example:
· Saturated fats decrease LDL receptor activity
· So as blood concentration of LDL increases less LDL is removed from blood and so
there are higher concentrations in blood and deposits in artery walls
· Polyunsaturated fats appear to increase the low density lipoprotein receptor activity so
they decrease the concentration of low density lipoprotein that is present in the
blood.
· Additionally, monounsaturated fats appear to be able to help to remove low density
lipoproteins from the blood, which is beneficial to health.
Explain that humans depend on plants for food as they are the basis of all food chains .
Plants are autotrophs and photosynthesise to convert light energy to glucose. They
change energy from the sun to energy in a chemical form that animals can use. So we
depend on plants for food.
Outline how selective breeding is used to produce crop plants with high yields, disease resistance and pest resistance.
Outline how selective breeding is used to produce domestic animals with high productivity.
Isolation  Choosing a pair of animals/plants that have the desired
characteristics and allow them to reproduce
Artificial Selection Offspring with the best combination of characteristics are
carefully selected and allowed to reproduce
Inbreeding/line breeding ^^ over many generations the characteristics are
exaggerated and the breeding programmes are carefully monitored
Farmers breed cattle for a high milk yield and for meat production, dairy cows can
produce a massive 40l or more milk a day.
Chickens are bred to produce eggs, or for meat. Egg layers can produce a huge 300 or
more eggs a year, whereas normal chickens only produce 20-30 eggs per annum.
Describe how the use of fertilisers and pesticides with plants and the use of antibiotics with animals can increase food production.
Fertilisers replace minerals in soil like nitrates, potassium and phosphates which were
removed by previous crops. They increase growth rate and size of crops produced.
Pesticides kill organisms that cause disease in crops which reduce yield or kill the crop.
The crops are sprayed with fungicides to reduce fungal growth in roots/leaves. Animals
are treated with pesticides to kill ticks living on their skin, e.g. sheep.
Infected animals can be given antibiotics to reduce spread of disease to animals farmed
close to each other. Otherwise the diseases can reduce growth and reproduction.
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19. Emily Summers
Describe the advantages and disadvantages of using microorganisms to make food for human consumption.
Advantages Disadvantages
Production of protein can be faster than People don’t want to eat fungal protein or
plant/animal protein food grown on waste
Production can be increased/decreased Isolation of the protein is hard considering
easily with demand the microorganisms are grown in big
fermenters and need to be isolated from
the material on which they grow
No animal welfare issues The protein must be purified to ensure it
isn’t contaminated
Good protein source for vegetarians e.g. The conditions needed to grow these
Quorn microorganisms are ideal for pathogens,
which can cause infection
No animal fat or cholesterol in protein The protein will not have the same
taste/texture as traditional protein sources
SCP production can be combined with
waste removal
Outline the methods that can be used to prevent food spoilage by microorganisms.
Cooking Heat denatures enzymes and proteins and
kills microorganisms
Pasteurising Heating at 72 degrees Celsius for 15
seconds and cooling rapidly to 4 degrees
Celsius to kill harmful microorganisms
Drying/salting/sugar coating Dehydrates microorganisms so water
leaves them by osmosis
Smoking Food has a hardened and dry outer
surface and the smoke has antibacterial
chemicals
Pickling An acid pH kills microorganisms by
denaturing enzymes and proteins
Irradiation Ionising radiation kills microorganisms by
distorting their DNA structure
Cooling/freezing Slows metabolic processes and growth,
reproduction by slowing down enzyme
activity. Does not kill them.
Canning Food is heated and sealed in airtight cans
Vacuum packing No air so microbes can’t respire
aerobically
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20. Emily Summers
Health and disease
Discuss what are meant by the terms health and disease
Health is a complete state of physical, mental and social well being as well as the
absence of disease or infirmity.
Disease is a departure from full health caused by a malfunction of the mind or body
Define and discuss the meanings of the terms parasite and pathogen.
Parasite Is an organism that lives in or on another living thing causing harm to the
host. External head lice Internal Tapeworm
Pathogen A general term for any organism that causes disease
Bacteria, fungi, viruses, protoctista
Describe the causes and means of transmission of malaria, AIDS/HIV and TB.
Malaria is caused by a eukaryotic organism, from the genus Plasmodium and most
commonly the species Plasmodium falciparum.
Malaria is spread by means of a vector. The female Anopheles mosquito carries the
plasmodium from an uninfected to an infected person, they feed on blood with adapted
mouthparts to penetrate a blood vessel and withdraw blood, malarial parasites live in
the erythrocytes of humans and feed on Hb.
HIV/AIDS
The virus enters the body and is un-active, but once the virus is active and
attacks/destroys T helper cells in the immune system your ability to resist infection is
greatly decreased. You are open to opportunistic infections which will eventually kill the
person with HIV/AIDS.
Exchange of bodily fluids, e.g. blood to blood, sharing needles, unprotected sex
Unscreened blood transfusions
Mother to baby- across the placenta or during breast feeding
TB
TB is caused by a bacterium, M Bovis and Mycobacterium tuberculosis.
It is usually in the lungs and although it is common it usually remains unactive or the
immune system controls it, it is transmitted by a droplet infection.
Overcrowding
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21. Emily Summers
Poor ventilation
Poor health, especially with HIV/AIDS
Poor diet
Homelessness
Contact with those who migrate from countries where TB is common
Discuss the global impact of malaria, AIDS/HIV and TB.
REMEMBER THE WORLD HEALTH ORGANISATION! They say good health is
a human right and see that in LEDC countries there may be:
Poverty
Lack of shelter and pure water
Poor nutrition and hygiene
Insufficient health services and insufficient education of disease
Malaria kills three million a year, but is limited to where the Anopheles can survive
which is tropical regions like Sub Saharan Africa. Global warming is a worry.
HIV/AIDS Pandemic. 45 million living with HIV/AIDS in 2005 and over half lived in sub
Saharan Africa.
TB Worldwide disease, new strains of Mycobacterium are resistant to drugs available
to treat it. Common in sub Saharan Africa but rising in Eastern Europe.
Define the terms immune response, antigen and antibody.
Immune response is the specific response to a pathogen involving the action of
lymphocytes and the production of antibodies.
Antigens are molecules that stimulate an immune response.
Antibodies are protein molecules that identify and neutralise antigens.
Describe the primary defences against pathogens and parasites (including skin and mucous membranes) and outline their
importance.
They try to prevent pathogens from entering the body, general mechanisms.
The skin
Main primary defence
Outer layer= epidermis
Keratinocytes are made by mitosis at the base of the epidermis, during migration
they dry out and the cytoplasm is replaced by keratin- called keratinisation. When
these cells reach the surface they aren’t alive anymore and the dead cells come
off, but this layer of dead cells are a good barrier to pathogens.
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22. Emily Summers
Mucous Membranes
In airways, lungs and digestive system
Goblet cells secrete mucus and mucus lines airway passages to trap pathogens.
Cilliated epithelium beats rhythmically to waft mucus to the back of the mouth
where it is swallowed down to the digestive system, the acidic stomach kills most
pathogens by denaturing their enzymes
Eyes are protected by tear fluid antibodies and enzymes
Ear canals are lined with wax to trap pathgogens
Describe, with the aid of diagrams and photographs, the structure and mode of action of phagocytes.
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23. Emily Summers
Describe, with the aid of diagrams, the structure of antibodies
Outline the mode of action of antibodies, with reference to the neutralisation and agglutination of pathogens.
Antibodies cover the pathogen
binding sites and prevent the
pathogen from binding to a host
cell and entering the cell
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24. Emily Summers
A large antibody can bind lots of pathogens together so the group of pathogens are too
large to enter a host cell.
Compare and contrast the primary and secondary immune responses
Compare and contrast active, passive, natural and artificial immunity.
Active Immunity Artificial Immunity
Exposure to antigen No exposure to antigen
Protection development takes a longer Protection is instant
period
Protection lasts a long while Protection lasts a short period
Memory cells made No memory cells made
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25. Emily Summers
Active Immunity Passive Immunity
Natural Catch the disease Antibodies from mother to
baby across placenta
Artificial Vaccination Injected with antibodies
Module 3 Biodiversity & Evolution
Biodiversity
Define the terms species, habitat and biodiversity
A species is a group of similar individual organisms with similar appearance,
biochemistry, physiology and genetics whose members are able to interbreed freely to
produce fertile offspring
A habitat is a place where the organism lives
Biodiversity is the variety of life, the range of living organisms to be found
Use Simpson’s Index (D) to calculate the biodiversity of a habitat, using the formula D = (n/N)2.
D = (n/N)2.
There are three species of flower in a field, red, white and blue.
There are eleven organisms all together, so N = 11
There are three of the red species, five of the white and three of the blue
D = 1 – ((3/11)2 + (5/11)2 + (3/11)2 = 1 – 0.36 = 0.64 Quite high!
Outline the significance of both high and low values of Simpson’s Index (D).
The closer to one the index is, the more diverse the habitat is. A high value indicates
high biodiversity in a habit which is beneficial, a low one indicates low biodiversity in a
habitat which isn’t so good, and may suggest that conservation methods might have to
be put in place.
Classification
Define the terms classification, phylogeny and taxonomy.
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26. Emily Summers
Classification is arranging organisms into groups based on similarities and differences
in appearance.
Phylogeny is the study of the evolutionary history of groups of organisms
Taxonomy is the study of classification
Explain the relationship between classification and phylogeny.
Describe the classification of species into the taxonomic hierarchy of domain, kingdom, phylum, class, order, family,
genus and species.
Outline the characteristic features of the following five kingdoms: Prokaryotae (Monera), Protoctista, Fungi, Plantae,
Animalia.
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27. Emily Summers
Kingdom Example Features
Prokaryote Bacteria Single cell, no nucleus,
smaller than 5 micrometres
Protoctista Algae Eukaryotic, single celled or
simple multicellular
Fungi Mould, yeast, mushroom Chitin cell wall, eukaryotic,
saprotrophic
Plantae Moss, fern, roses Eukaryotic, multicellular,
cellulose cell wal, autotrophic
Animalia Mammals, reptiles, birds, fish, Heterotrophic, eukaryotic, no
insects cell wall, multicellular
Outline the binomial system of nomenclature and the use of scientific (Latin) names for species.
One international name in latin with two parts is given to every organism. The
first part is the genus and is a capital letter, and the second is the species and is
lower case- typed in italics or underlined when written. E.g. Homo sapien
Helps to avoid confusion within scientists as they’re standard scientific names.
Use a dichotomous key to identify a group of at least six plants, animals or microorganisms.
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28. Emily Summers
Discuss the fact that classification systems were based originally on observable features but that more recent
approaches draw on a wider range of evidence to clarify relationships between organisms, including molecular evidence.
Early classification systems simply used observable features to put organisms
into groups, but this is problematic because the fact that some organisms look
similar doesn’t mean they’re closely related, e.g. sharks and whales look similar
and live in the sea, but sharks are fish and whales are mammals! Classification
systems today are based on more evidence, like:
Molecular evidence protein and DNA similarities, e.g. how it’s stored,
closeness of bases.
Anatomical Similarities in structure and function of body parts
Behavioural evidence Similarities in behavior and social organization of
organisms
Compare and contrast the five kingdom and three domain classification systems.
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29. Emily Summers
Evolution
Define the term variation.
Variation  Presence of variety of differences between individuals
Discuss the fact that variation occurs within as well as between species.
Describe the differences between continuous and discontinuous variation, using examples of a range of characteristics
found in plants, animals and microorganisms.
Continuous variation  Variation in which there is a full range of intermediate
phenotypes between two extremes
Discontinuous variation  Variation in which there are discrete groups of phenotypes
with few or no individuals in between
Continuous Discontinuous
Height Dangling/attached ear lobes
Handspan Gender
Weight Blood groups
Shoe Size Bacteria with absence/presence of flagella
Continuous Discontinuous
Affected by environment & genes Unaffected by environment, just genes
Quantitative overlaps Qualitative no overlaps
Controlled by a large number of genes Controlled by few/one gene (monogenic)
(polygenic)
No distinct categories Distinct categories
Like heart rate, muscle efficiency, IQ, growth This type of variation is rare in animals
rate, rate of photosynthesis but abundant in plants, like seed colour,
petal colour, etc.
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30. Emily Summers
Explain both genetic and environmental causes of variation.
Genetic Environmental
Genes from our parents Linked with genetic
Combination of alleles Like height is somewhat
Not the same in any other living determined by your genes but
thing apart from identical twins the environment plays a part on
Never a complete match the height you will reach. (diet)
Human cells have 25,000 Environmental changes affect
different genes and a lot of them what genes in animals and plants
have more than one allele, so it are activated, bringing about
isn’t likely that any two changes we see
individuals will have the exact Obesity diet  socio-economic
same allele combinations. issues. Westernized society has
more overweight people than
ledc’s
Outline the behavioural, physiological and anatomical (structural) adaptations of organisms to their environment
Behavioural Physiological/Biochemical Anatomical
•Behaviour of an organism •A physiological/biochemical • Any structure that
that enables it to survive it's adaptation that ensures enhances survival of the
living conditions. Like when correct functioning of cell organism is an adaptation.
you touch an earthworm it processes. Like yeast can Like bacteria that have
quickly contracts and goes respire sigars an/aerobically flagella to allow them to
back into it's burrow. This is to get energy depending on move indepedently.
a behavioural adaptation the amount of O2 in the Structural adaptation.
that avoids it being eaten. environment. Producing
correct enzymes to respire
the sugars in the
environment falls under this
category.
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31. Emily Summers
Explain the consequences of the four observations made by Darwin in proposing his theory of natural selection.
Individual in a species have differences from each other – so variation is present.
Offspring bare resemblance to their parents – those characteristics are inherited.
There are more offspring produced than survived to maturity - they suffer from
predation, disease and competition.
Populations have constant sizes
“Darwin concluded that individuals that were better adapted to their environment
compete better than the others, survive longer and reproduce more, so passing on more
of their successful characteristics to the next generation. Darwin used the memorable
phrases survival of the fittest, struggle for existence and natural selection.” Biology Mad
Define the term speciation.
Formation of a new species from the evolution of one species
geographical isolation which is an example of allopatric speciation
reproductive isolation which is an example of sympatric speciation
Discuss the evidence supporting the theory of evolution, with reference to fossil, DNA and molecular evidence.
Outline how variation, adaptation and selection are major components of evolution.
Discuss why the evolution of pesticide resistance in insects and drug resistance in microorganisms has implications for humans.
Conserving biodiversity
Outline the reasons for the conservation of animal and plant species, with reference to economic, ecological, ethical and
aesthetic reasons.
Discuss the consequences of global climate change on the biodiversity of plants and animals, with reference to changing
patterns of agriculture and spread of disease.
Explain the benefits for agriculture of maintaining the biodiversity of animal and plant species.
Describe the conservation of endangered plant and animal species, both in situ and ex situ, with reference to the
advantages and disadvantages of these two approaches.
Discuss the role of botanic gardens in the ex situ conservation of rare plant species or plant species extinct in the wild,
with reference to seed banks.
Discuss the importance of international cooperation in species conservation with reference to the Convention in
International Trade in Endangered Species (CITES) and the Rio Convention on Biodiversity.
Discuss the significance of environmental impact assessments (including biodiversity estimates) for local authority planning
decisions
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32. Emily Summers
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