AS Biology Unit F212 Molecules, Biodiversity, Food and Health

2.1.1 Biological Molecules(a) describe how hydrogen bonding occurs between water molecules, and relate this, and

other properties of water, to the roles of water in living organisms

Water is attracted to ions and polar substances so it is a good solvent. Water is reactive so can be used during hydrolysis.

(b) describe, with the aid of diagrams, the structure of an amino acid

Structure of Amino acid

Example- Glycine

(c) describe, with the aid of diagrams, the formation and breakage of peptide bonds in the synthesis and hydrolysis of dipeptides and polypeptides

Amino acids have the same general structure, a carboxyl group and a amino group (-NH2). The ‘R’ group is variable.

Condensation reaction where 2 amino acids form a peptide bond between each other. Water is produced as a result.

Hydrolysis reaction where peptide bond is broken. Water is used as a result of this.

Reversible reaction

(d) explain, with the aid of diagrams, the term primary structure

(e) explain, with the aid of diagrams, the term secondary structure with reference to hydrogen

bonding

(f) explain, with the aid of diagrams, the term tertiary structure, with reference to hydrophobic and hydrophilic interactions, disulfide bonds and

ionic interactions

Ionic interactions- weak attractions between oppositely charged parts of the molecule.

Disulphide bonds- 2 molecules of animo acids close together, sulphur atoms in them bond together. (Cysteine).

Hydrophobic- water repelling groups near together in a protein clump.

Hydrophilic- water attracting groups are likely to be pushed outside, affecting proteins final structure.

(g) explain, with the aid of diagrams, the term quaternary structure, with reference to the structure of haemoglobin

Quaternary structure tends to be determined by the tertiary, when it involved multiple polypeptides. Haemoglobin is a quaternary protein as it involves 4 polypeptide chains.

(h) describe, with the aid of diagrams, the structure of a collagen molecule

Collagen is a strong protein that is fibrous. It is used as a supportive tissue in animals. It consists of 3 polypeptide chains that are bound tightly together in a triple helix held by covalent

bonds. Minerals can bind to increase rigidity. Tendons are made mostly fro collagen.

Walls of the artery contain collagen to prevent it from bursting ender high pressure.

Cosmetic use- on lips for fuller appearance.

(i) compare the structure and function of haemoglobin (as an example of a globular protein) and collagen (as an example of a fibrous protein)

Haemoglobin CollagenGlobular protein Fibrous ProteinLarge variety of amino acids in it’s primary structure

35% of primary structure is glycine

Has a prosthetic group- ‘haem’ group Doesn’t contain a prosthetic groupMostly wound into alpha helix structures Mostly left handed helix structures

(j) describe, with the aid of diagrams, the molecular structure of alpha-glucose as an example of a monosaccharide carbohydrate

Monosaccharide carbohydrate, known as a hexose (6 carbons) sugar in every molecule. Solubility is dependant on structure so it can be transported in water. It’s the source of energy in plants and animals, the chemical bonds contain a lot of energy within them.

(k) state the structural difference between alpha- and beta-glucose

(l) 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)

(m) compare and contrast the structure and functions of starch (amylose) and cellulose;

Structural difference- OH group is in opposite ends.

Condensation- H2O removed!

Hydrolysis- H2O breaks glycosidic bond.

Starch- is made up of many ‘α glucose’ molecules. Starch acts as a energy storage.

Cellulose- is made up of many ‘β glucose’ molecules. Cellulose acts as support, inside a plant cell wall it helps strengthen it. Most animals and plants do not have the enzyme to break down cellulose.

(n) describe, with the aid of diagrams, the structure of glycogen

(o) explain how the structures of glucose, starch (amylose), glycogen and cellulose molecules relate to their functions in living organisms

Carbohydrate Example Characteristics Function in Organisms

Monosaccharide monomers

Glucose (6 Carbon sugar)

Small, soluble, sweet, crystalline

Energy via respiration

Deoxyribose (5 Carbon sugar)

Part of DNA information molecule

Disaccharide dimers Maltose (2 glucoses) Small, soluble, sweet & crystalline

Sugar obtained when starch is broken down in hydrolysis, can be split to glucose for more respiration

Polysaccharide polymers

Starch & glycogen Large molecules, many alpha glucose molecules joined by condensation. Insoluble in H2O and form granules

Energy store in plants as cellulose and glycogen in animals and fungi

Cellulose Large molecules of many beta glucose molecules joined by condensation. Insoluble in H2O and are strong.

Structural in plants for cell walls.

Excess glucose is stored as glycogen in animals.

It is made by 1-4 and 1-6 glycosidic bonds making the molecule branched. This allows lots of glucose to be released at a time of need.

(p) compare, with the aid of diagrams, the structure of a triglyceride and a phospholipid

(q) explain how the structures of triglyceride, phospholipid and cholesterol molecules relate to their functions in living organisms

Triglyceride molecules act as a energy storage. The hydrocarbon tails contain a lot of chemical energy when broken down is released. Lipids release contains twice as much energy compared with

carbohydrates.Triglycerides are hydrophobic so they repel water and do not affect water potential as it is not

soluble.Phospholipids have a hydrophilic head and a hydrophobic tail, the head faces outwards and the tail

faces inwards in the bilayer. This makes it difficult for Na+ ions and glucose molecules to pass through.

Cholesterol is a lipid found in the cell membrane and provides mechanical stability to it, it is also used to make steroids. It is made up of a hydrocarbon ring bonded with a hydrocarbon tail, the

hydrocarbon head has a hydroxyl group attached to it making it soluble.

Phospholipids are similar to triglyceride, the exception being

that one fatty acid chain has been replaced by a hydrophilic phosphate head. The fat tail is

hydrophobic.

Phospholipids form the cell membrane; this prevents water soluble molecules from passing

through.

(r) 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)

Benedict’s Test- Test For Reducing and Non-reducing Sugars

Reducing Sugars Add Benedict’s solution to the substance. Heat to 80 degrees. Reducing sugar= blue to brick red. Non-reducing sugar= no colour change, stays blue.

Non-reducing sugars Add HCl, and boil, hydrolysis will split the bonds. e.g Sucrose= Glucose + Fructose. Add Alkali to neutralize pH (NaCO3). Add Benedict’s solution to the substance. Heat to 80 degrees. Colour change= blue to brick red.

Iodine Test- Test for Starch Add iodine to a potassium iodide solution to the sample. Positive result= yellow/brown to dark blue/black (colour change). Negative result= no visible change (colour stays the same).

Emulsion Test Mix sample with ethanol. (Dissolves lipids). Pour solution into water. Positive result= milky white emulsion near top of water.

Biuret Test Add Biuret Reagent to sample. (Reagent contains sodium hydroxide and copper sulphate). Reacts with peptide bonds in protein. Positive result= Solution turning purple means

there is protein. Negative result= No change, stays blue.

(s) describe how the concentration of glucose in a solution may be determined using colorimeter

Colorimeter measures the absorbance of light in a solution, the more concentrated the solution is the more the absorbance of light.

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.

Module 2.1.2 Nucleic Acid

(a) 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);

Nucleotide

Phosphate Group Adenine and Thymine bond

together via 2 hydrogen bond.

Cytosine and Guanine bond together via 3 hydrogen bonds.

Deoxyribose Join together via covalent

bonding between phosphate group and pentose sugar.

(b) 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);

RNA is a polynucleotide, as it is made up more many nucleotide monomers.

(c) describe, with the aid of diagrams, how hydrogen bonding between complementary base pairs (A to T, G to C) on two antiparallel DNA polynucleotides leads to the formation of a DNA molecule, and how the twisting of DNA produces its ‘double-helix’ shape (HSW1);

(d) outline, with the aid of diagrams, how DNA replicates semi-conservatively, with reference to the role of DNA polymerase;

Enzyme ‘DNA Helicase’ breaks the hydrogen bonds between the two polynucleotide strands, exposing bases.

Each original strand is a template for a new strand, free-floating DNA nucleotides join the exposed bases on each of the original templates by complementary base pairing (A-T, C-G).

Nucleotides on new strand are joined by ‘DNA Polymerase’, and new hydrogen bonds are formed between bases of new and old strand.

Each DNA molecule contains one strand from the original and one new strand.

(e) state that a gene is a sequence of DNA nucleotides that codes for a polypeptide (HSW3); Gene- is a length of DNA that carries the code for the synthesis of one or more specific polypeptides.

(f) 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 for the instructions for proteins, they code for the amino acid sequence present in the protein. This is a gene.There are 3 forms of RNA:

Messenger RNA- is a strand complementary to a strand of a DNA molecule. Ribosomal RNA- in ribosome’s. Transfer RNA- carries amino acids to the ribosome’s and they are bonded together to

form a polypeptide.

(a) state that enzymes are globular proteins, with a specific tertiary structure, which catalyse metabolic reactions in living organisms;

Enzymes are: Globular proteins (soluble)- like haemoglobin Able to break down/build up molecules Enzyme=Biological Catalyst Specific- can only catalyse a reaction with only one type of substrate Globular structure has pockets called ‘active site’ Activity effected by- Temperature and pH Large molecule- made up of hundreds of amino acid (help keep its specific tertiary

shape). All primary/secondary and tertiary is involved in maintaining shape of active site.

(b) state that enzyme action may be intracellular or extracellular; Extracellular- enzymes that catalyse reactions outside of the cell.

Eg. Mould produces extracellular enzymes to break down bread. Intracellular- enzymes that catalyse reactions inside of the cell.

Eg. Phagocytes use lytic enzymes to break down pathogens inside the cell.

(c) 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: Lowers activation energy- reactions can take place in lower temperatures with the

presence of enzymes. Active site is complementary to the shape of the substrate (specific).

(d) describe and explain the effects of pH, temperature, enzyme concentration and substrate concentration on enzyme activity;

pH (measure of H+ ions)-H+ Ions are positive so are attracted to negative charged ions/parts of a molecule and are repel positive ions/parts of a molecule. Hydrogen and ionic bonds hold the tertiary structure of the enzyme in place so the active site maintains its specific shape. The bonds are there due to electrostatic attractions between opposite charges of the amino acids making up the enzyme.Hydrogen ions can interfere with these bonds and can alter the specific tertiary shape.Enzymes have their own optimum pH, the H+ ion concentration gives the enzyme its best overall shape. Enzymes work in a narrow pH range, and their pH normally changes with their location. Eg. Pepsin, works best in pH2, convenient in stomach.

Temperature

Increasing heat gives more kinetic energy to molecules, so they move more and vibrate.

Vibrations strain the bonds holding the molecule together.

In a large molecule (enzymes) the vibrations can break the weaker bonds such as hydrogen and ionic bonding.

The weaker bonds are in abundance in a enzyme to hold its specific tertiary shape. Increasing temperature=increasing bonds broken. Tertiary structure has less support holding its shape needed for the shape of the

active site. Rate of reaction decreases as substrates cannot fit active site. If enough bonds are broken, the entire tertiary structure unravels and the enzyme

stops working. Denaturing.

Concentration

Increasing enzyme concentration increases the rate of reaction up to a certain point. This is because the concentration of substrates becomes a limiting factor.

Increasing substrate concentration increases the rate reaction up to a certain point. This is because the number of active sites available is used up. So the concentration of enzymes becomes a limiting factor.

(e) describe how the effects of pH, temperature, enzyme concentration and substrate concentration on enzyme activity can be investigated experimentally;

Variable Method of Keeping Constant

Reasons

Temperature Carrying out the enzyme controlled reaction in a water bath with thermostat

Room temperature changes and fluctuations in the 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 volume of enzyme-solution

Rate of reaction depends on concentration of enzyme molecules present; using accurate volumes of enzyme solution gives a true constant conc. Of enzyme molecules

Living tissue Mass of tissue has to be accurate

Assume that the pieces of tissue have the same number of enzyme molecules

Whole pieces of tissue same surface area and mass

The number of enzymes that have contact with substrate affects rate of reaction, e.g. surface area

Substrate Concentration Accurately measured substrate volume/mass

Rate of reaction depends on substrate molecule concentration

pH value Use pH buffers by keeping H+ concentration constant

Rate of reaction depends on pH because it alters the shape of the active site of the enzyme

(f) 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 similar shape to substrate. Occupy active site forming enzyme-inhibitor complex but no products are formed. Enzyme cannot catalyze the reaction so rate of reaction slows down. (Depends on

inhibitor and substrate concentration).Non-competitive Inhibitors:

Don’t occupy active site but attaches somewhere else, changes the tertiary structure of the enzyme.

Shape of active site changes, substrate cannot fit no more. Enzyme cannot catalyse the reaction so rate of reaction slows down. (Increasing

concentration has no effect).

Reversible Inhibitors- when the inhibitor is not there permanently so afterwards the enzyme is not affected.Non-reversible Inhibitors- usually non-competitive, the enzyme is denatured.

(g) explain the importance of cofactors and coenzymes in enzyme-controlled reactions;

Coenzymes take part in a 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.

(h) state that metabolic poisons may be enzyme inhibitors, and describe the action of one named poison;

Lots of poisonous substances have their effects due to inhibiting or over-activating enzymes.Potassium Cyanide inhibits respiration cells; it is a non-competitive inhibitor that binds to a vital respiratory enzyme, cytochrome oxidase, in the mitochondria. When cytochrome oxidase is inhibited, O2 cannot be used to produce ATP. The organism has to respire anaerobically producing lactic acid which increases the acidity of the blood.

(i) state that some medicinal drugs work by inhibiting the activity of enzymes;

Viral infections are treated by using chemicals that act as protease inhibitors; this stops viruses from creating proteins which is vital for their protein coats. These inhibitors are usually competitive.

Biology Unit 2- Module 2.2.1 Food and Health

(a) define the term balanced diet A diet which includes all needed nutrients for health in appropriate portions.

(b) explain how consumption of an unbalanced diet can lead to malnutrition, with reference to obesity Malnutrition is caused by an unbalanced diet; diseases caused by this can be anorexia and obesity.Obesity- having a BMI of 30+ you are classed as ‘obese’ having 20% more weight than is recommended for your height. This happens when you consume too much or too little of a certain food group. Other factors add to this.

BMI= Mass in kg/(Height in m)2

(c) discuss the possible links between diet and coronary heart disease (CHD)There are many links between diet contributing to CHD.CHD is the result of fatty deposits in the coronary artery wall. (Atherosclerosis)Salt- decreases blood water potential so more water moves into the blood causing blood pressure to increase, causing hypertension. This is high blood pressure continuously even during diastole when the heart muscle is relaxing (blood pressure is meant to be low). High blood pressure can damage the inner lining of the arteries and contribute to causing atherosclerosis. Lipids- animal fats are usually saturated while plant fats are usually unsaturated. Saturated fats are bad for the human body, part of LDL, while unsaturated fats are healthy, part of HDL.Cholesterol- this has similar properties to triglycerides, can be found in meat, eggs and dairy products. Concentration of cholesterol in blood should not exceed 5.2 mmol dm-3.

(d) 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 lipoprotein (LDL) HDL’s are made up of unsaturated fats, proteins and cholesterol; they carry fats from body tissues to the liver. Cells in the liver have receptor sites that let HDL’s bind to the cell surface. In the liver the cholesterol is used in cell metabolism to make bile or it can be broken down. High levels of HDL are linked with reducing cholesterol levels of blood.HDL’s decrease the amount of fats deposited in the artery walls caused by atherosclerosis and even helps to remove the deposits of it.LDL’s are made up of saturated fats, cholesterol and proteins; they carry cholesterol from the liver to the tissues.Tissue cells contain receptor sites on the cell surface membrane in which LDL’s can bind with. If there is a lot of saturated fats and cholesterol then the concentration of LDL’s in the blood increases.Different fats affect the LDL receptor sites:

Saturated fats decrease LDL receptor activity, less LDL is removed from the blood causing it to be deposited in the artery walls. Concentration in the blood increases as well.

Polyunsaturated fats increase LDL receptor activity allows more LDL’s to be removed from the blood decreasing its concentration.

Monounsaturated fats appear to help remove LDL’s from the blood.

(e) explain that humans depend on plants for food as they are the basis of all food chains. (No details of food chains are required)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.

(f) outline how selective breeding is used to produce crop plants with high yields, disease resistance and pest resistance

Isolation- choosing a pair of animals/plants that have a desired characteristic and allow them to reproduce.

Artificial Selection- offspring with the best characteristics are carefully selected and allowed to reproduce.

In breeding/line breeding- over the generations certain characteristics are exaggerated and breeding programmes are carefully monitored.

(g) outline how selective breeding is used to produce domestic animals with high productivity Farmers breed cattle for high milk yield as well as high meat yield, e.g dairy cows are able to produce a massive 40L of milk per day.Chickens are bred to produce high numbers of eggs and high yield of meat. e.g egg layers can lay 300+ eggs per year while normal chickens only 20+.

(h) describe how the use of fertilisers and pesticides with plants and the use of antibiotics with animals can increase food productionFertilizers replace used mineral, such as nitrates, potassium and phosphates, these minerals were used by previous crops. They increase growth rate and the size of crops produced.Pesticides kill organisms that cause disease in crops which reduce yield or kills the plant.Fungicides are used to kill fungi growing on leaves/roots.Animals are treated with pesticide to kill ticks living on them.Infected animals can be treated with antibiotics to prevent the disease from spreading or the disease can reduce growth and population.

(i) describe the advantages and disadvantages of using microorganisms to make food for human consumptionAdvantages DisadvantagesProduction of protein can be faster than plant/animal protein

People don’t want to eat fungal protein or food grown on waste

Production can be increased/decreased easily with demand

Isolation of the protein is hard considering 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. Quorn

The conditions needed to grow these 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

(j) outline how salting, adding sugar, pickling, freezing, heat treatment and irradiation can be used to prevent food spoilage by microorganisms. Cooking Heat denatures enzymes and proteins

and kills microorganismsPasteurising 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

(a) discuss what is meant by the terms health and disease; Health- the state of complete physical, mental and social well-being and the absence of disease and infirmities.Disease- a departure of full health caused by malfunction of the body or mind.

(b) define and discuss the meanings of the terms parasite and pathogen; Parasite- an organism that lives in or lives on another living thing causing harm to the host.Pathogen- a disease causing organism.Bacteria, fungi, viruses and protoctista.

(c) describe the causes and means of transmission of malaria, AIDS/HIV and TB Malaria is spread by means of a vector. The female anopheles mosquito carries the plasmodium from an infected person to a non-infected person, as they feed on blood with adapted mouth parts to penetrate vessels and withdraw blood. Malaria parasite lives in the erythrocytes of humans and feeds on Hb.

HIV/AIDS is a virus that enters the body un-active, once active it kills T-helper cells in the immune system and the ability to resist infection in greatly decreased. This eventually kills a person as they a prone to many different illnesses. This is spread by:

exchange of bodily fluids unscreened blood transfusion Mother to baby- (from placenta or breast feeding).

TB is caused by bacterium, it is usually in the lungs and is common but remains un-active or the immune system controls it. It is spread by droplet infection.It can be spread by:

Overcrowding Poor ventilation Poor health (especially with AIDS/HIV) Poor diet Homelessness Contact with people from countries where TB is common.

(d) discuss the global impact of malaria, AIDS/HIV and TB (HSW4, 6a, 7c);

WHO says that good health is a human right, LEDC are more prone to disease due to: poverty lack of shelter and clean water poor nutrition and hygiene insufficient health services and insufficient education on disease

Malaria- kills 3 million people a year, but is limited to where the anopheles can survive (in tropic countries). Global warming is a worry for this.HIV/AIDS- Pandemic, 45 million people living with HIV/AIDS, almost half living in sub-Saharan Africa.TB- worldwide disease, common in Africa and Asia, new strains are appearing resistant to drugs in Eastern Europe.

(e) define the terms immune response, antigen and antibody; Immune response- is the specific response to a antigen by means of lymphocytes and the releasing of antibodies.Antigen- are molecules that stimulate an immune response.Antibodies- are protein molecules that identify and neutralise antigens.

(f) describe the primary defences against pathogens and parasites (including skin and mucus membranes) and outline their importance. (No details of skin structure are required);

Primary defences are methods to prevent pathogens from entering the body- The epidermis, outer layer, which is the skin is a protective barrier of dead cells. Mucous membranes- in airways lungs and digestive systems. Goblet cells secrete mucus which trap pathogens. Ciliated epithelial waft the mucus

up the throat or down to the stomach to be killed in the stomachs acid. Eyes are protected by tear fluid (has antibodies and enzymes). Ear canals are lined with wax to trap pathogens.

(g) describe, with the aid of diagrams and photographs, the structure and mode of action of phagocytes;

(h) describe, with the aid of diagrams, the structure of antibodies;

(i) outline the mode of action of antibodies, with reference to the neutralisation and agglutination of pathogens;

Agglutination- Large antibodies can bind to more than one pathogen making a group preventing them from binding or entering a host.

Neutralisation- Antibodies covers the pathogens binding site to prevent it from binding and entering a host and entering the cell.

(j) describe the structure and mode of action of T lymphocytes and B lymphocytes, including the significance of cell signalling and the role of memory cells;

Cell signalling- is important as immune response depends on the communication between cells.

Identification- Pathogen has ‘foreign antigens’. Distress signals- Lysosomes in host cell may damage pathogen, antigen can then

bind to host. This causes a distress signal to be sent, and also acts as a indicator to what cell is infected.

Antigen presentation- Macrophages partially break down the pathogen and use its antigens to find the particular lymphocyte that can neutralise the antigen.

Pathogen engulfed by cells from the immune system

Removal of antigens from pathogen

Antigens presented on surface of engulfing cells

Selection of correct T killer and T helper cells.

Reproduction of T helper cells. (clonal expansion).

Reproduction of T killer cells. (clonal expansion).

Reproduction of B cells

Activation of B cells

Release of interleukins

Same B cell clones differentiate to make

plasma cells.

Some B cell clones differentiate to make

B memory cells.

T killer cells search for infected cells.

T killer cells attach to infected cells.

T killer cells secrete toxic substances (hydrogen peroxide) into infected cells to

kill cell and pathogen.

Plasma cells manufacture antibodies.

Memory cells circulate in body providing

immunology memory.

(j) compare and contrast the primary and secondary immune responses;

(l) compare and contrast active, passive, natural and artificial immunity; Active Immunity Artificial ImmunityExposure to antigen No exposure to antigenProtection development takes a longer period

Protection is instant

Protection lasts a long while Protection lasts a short periodMemory cells made No memory cells made

Active Immunity Passive ImmunityNatural Catch the disease Antibodies from mother to

baby across placentaArtificial Vaccination Injected with antibodies

(m) explain how vaccination can control disease; Provides immunity to all people who are at risk of a disease, there are 2 ways to use vaccination:

Herd vaccination- provide immunity to all/most of the population at risk. Once enough people are vaccinated the disease can no longer spread.

Ring vaccination- used when a new case of disease is reported. All people within the vicinity of the disease are vaccinated.

(n) discuss the responses of governments and other organisations to the threat of new strains of influenza each year; Pathogenic organisms can form a new strain by mutation. Diseases caused by viruses are a particular threat.Influenza- causes many deaths, vaccines provide little immunity as the virus can mutate to form a new strain. This affects the respiratory system so old people are more at risk, so they are vaccinated against it.

(o) outline possible new sources of medicines, with reference to microorganisms and plants and the need to maintain biodiversity;

New drugs are needed because: New diseases emerge Many diseases with no effective treatment Some antibiotics are less effective as pathogen evolves

New medicines discovered- By accident- discovery of penicillin. Traditional medicines- use of plants. Anaesthetics- unripe poppies can make opium which reduces activity in the central

nervous system, prevents pain. Observation of wildlife- many animals self-medicate, e.g some animals rub citrus oils

on their coat as it acts as a insecticide.

(p) describe the effects of smoking on the mammalian gas exchange system, with reference to the symptoms of chronic bronchitis, emphysema (chronic obstructive pulmonary disease) and lung cancer;

Tar:Short-term effects:

Increases diffusion distance for O2 and CO2. Paralyses or destroys cilia, mucus remains in the airways. Stimulates goblet cells, which produce more mucus, which remains in the airway

including the bacteria caught in it.Long-term effects:

Smoker’s cough- an attempt to move the mucus stuck in the airway. Constant cough- damages delicate lining of airways which is replaced by thick, scar

tissue.Lung cancer-

Cancer is when the gene for cell division mutates and the cells controls uncontrollably.

Often forms are fork of bronchi where smoke hits. Often takes 20-30yrs to develop.

Chronic bronchitis: Inflammation of the lining of the airways. Damage to cilia and overproduction of mucus. Constant coughing.

Emphysema: Loss of elasticity of the alveoli. Lungs have reduced SA. Shortness of breath.

Chronic Obstructive Pulmonary Disease (COPD): Combination of the above diseases.

(q) describe the effects of nicotine and carbon monoxide in tobacco smoke on the cardiovascular system with reference to the course of events that lead to atherosclerosis, coronary heart disease and stroke;

Nicotine is an addictive chemical that does many things: Makes nervous system more sensitive, makes the smoker fell more alert. Causes release of hormone adrenaline, which increases heart rate, breathing rate

ect. Causes constriction of arterioles, reduces blood flow and oxygen delivery. Affects platelets making them sticky. Increases the risk of blood clot and thrombosis.

Carbon Monoxide: Enters red blood cells and binds with haemoglobin. Combines more readily than O2.

Reduces the oxygen-carrying ability of the blood, body detects low levels of O2 so heart rate increases.

CO damages lining of arteries.

Atherosclerosis- builds up of white blood cells, fats and platelets under the lining of the inner endothelium. This hardens and becomes a plaque which bulges out narrowing the lumen of the artery. This can eventually burst or block the artery.

Thrombosis- Blood clot=thrombus

CHD (Coronary Heart Disease) - 3 forms: Angina- severe pain in chest. Myocardial Infarction- death of a part of a heart muscle. Heart failure when heart cannot sustain pumping action.

Stroke- death of part of the brain- caused when there is insufficient blood flow to the brain.

(r) evaluate the epidemiological and experimental evidence linking cigarette smoking to disease and early death;

Facts and figures between cigarette smoking and lung cancer is evident. Comparison data is called epidemiology. Links to lung disease:

Smoker is 18 times more likely to get lung cancer than a non-smoker. 25% of smokers die of lung cancer. Heavy smokers are 25 times more likely to die of lung cancer. Chances of developing lung cancer are reduced once a person stops smoking.

Links to other lung diseases: COPD is rare in non-smokers. 98% with emphysema are smokers. 20% of smokers have emphysema

Experimental evidence- Dogs were made to inhale unfiltered cigarette smoke and began to show signs of

COPD and lung cancer. Dogs were made to inhale filtered smoke and began to show slight signs of COPD

and early stages of lung cancer. Tar was placed on the skin of mice and they developed skin cancer.

Module 3 Biodiversity and Evolution

(a) define the terms species, habitat and biodiversity; Species- A group of similar individual organisms that are similar in

appearance, anatomy, physiology, biochemistry and genetics. Habitat- the place where an organism lives. Biodiversity- the range of organisms that can be found in a habitat.

(b) explain how biodiversity may be considered at different levels; habitat, species and genetic;

Biodiversity is about the structural and functional variety in the living world. It can be considered in:

Habitat- the range of habitats in which different species lives. (Ponds, fields, lawn are all different habitats).

Species- the differences between species found in a habitat. (Can be structural differences e.g. ant and tree but can be functional differences e.g. bacteria that cause decay and bacteria that help us decay food).

Genetics- genetic variation between individuals belonging to the same species. (variation within species that ensure we do not look alike).

(c) explain the importance of sampling in measuring the biodiversity of a habitat; Human activities affect the environment in many different ways. We study the effects in order to assess the impact that we have on the environment. Environmental impact assessments are vital parts of planning processes.

(d) describe how random samples can be taken when measuring biodiversity; Random samples- selecting portions of the habitat at random and studying them in detail.Random samples= more representative, less bias.Method: Take samples regularly distances across the habitat.PlantsUse of random quadrat- quadrat is placed at random on the habitat; the plants with the quadrat are identified.

Abundance is measured in ACFOR scale. A AbundantC CommonF FrequentO ObviousR Rare

Transects- stretching a long tape measure along a habitat and taking record of the species along it.AnimalsSweep netting- sweep net through vegetation, release organisms onto white sheet to be counted.Collecting from trees- a white sheet is held underneath a branch, the branch is knocked so small organisms fall onto it to be counted.Light trap- UV light attracts insects, which eventually fall into a vessel of alcohol below to be counted.Pitfall trap- animals fall into a container buried in the soil.

(e) describe how to measure species richness and species evenness in a habitat;

Species Richness- the number of species in a habitat. The more species present the richer the habitat.Species evenness- the relative abundance of individuals in each species.Smaller animals: Mark and recapture technique.(C1xC2)/C3C1= capturing a sample of animals and marking them in a non-harmful way. Release them then leave more traps.C2= the number of organisms recaptured.C3= the number of marked organisms recaptured.

(f) use Simpson’s Index of Diversity (D) to calculate the biodiversity of a habitat,

using the formula D = 1-((n/N)2) (HSW3); 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!

(g) outline the significance of both high and low values of Simpson’s Index of Diversity (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.

(h) discuss current estimates of global biodiversity.

We are not sure how accurate they are because:

They do not include marine species New species are being found

Evolution and speciation in continuing Many species are continuing

Some species are becoming extinct

Module 2.3.2 Classification

a) define the terms classification, phylogeny and taxonomy; Classification- process of placing living tings into groups according to their similarities.Phylogeny- the study of the evolutionary history of groups of organisms.Taxonomy- is the study of classification.

(b) explain the relationship between classification and phylogeny; Relationship-

(c) describe the classification of species into the taxonomic hierarchy of domain, kingdom, phylum, class, order, family, genus and species;

(d) outline the characteristic features of the following five kingdoms: Prokaryotae (Monera), Protoctista, Fungi, Plantae, Animalia;

Kingdom Example Features

Prokaryote Bacteria Single cell, no nucleus, smaller than 5 micrometers, no chromosomes.

Protoctista Algae Eukaryotic, single celled or simple multicellular, mostly free living.

Fungi Mould, yeast, mushroom Chitin cell wall, eukaryotic, saprotrophic

Plantae Moss, fern, roses Eukaryotic, multicellular, cellulose cell wall, autotrophic nutrition.

Animalia Mammals, reptiles, birds, fish, insects

Heterotrophic nutrition, eukaryotic, no cell wall, multicellular

(e) outline the binomial system of nomenclature and the use of scientific (Latin) names for species;

(f) use a dichotomous key to identify a group of at least six plants, animals or microorganisms;

(g) discuss the fact that classification systems were based originally on observable features but more recent approaches draw on a wider range of evidence to clarify relationships

between organisms, including molecular evidence;(h) compare and contrast the five kingdom and three domain classification

Module 2.3.3 Evolution

(a) define the term variation; Variation- the presence of variety, the differences between individual organisms of the same species.

(b) discuss the fact that variation occurs within as well as between species; Variation occurs:

Within a species- eye/hair colour Between species- birds can fly but cats cannot

(c) describe the differences between continuous and discontinuous variation, using examples of a range of characteristics found in plants, animals and

microorganisms; Discontinuous Variation-

This is where individuals fall into a number of distinct categories There are no intermediate values/ values measured across a complete range Either you have the characteristic or you don’t

Eg.Sex: Male/Female (Mammals), Female/ Hermaphrodite (Plants)

Continuous Variation- Occurs when there is a complete range of values

Eg. Height (154cm, 167cm, 176cm ect)

Continuous DiscontinuousHeight Dangling/attached ear lobesHandspan GenderWeight Blood groupsShoe Size Bacteria with absence/presence of

flagella

Continuous DiscontinuousAffected by environment & genes Unaffected by environment, just genesQuantitative overlaps Qualitative no overlapsControlled by a large number of genes (polygenic)

Controlled by few/one gene (monogenic)

No distinct categories Distinct categoriesLike heart rate, muscle efficiency, IQ, growth rate, rate of photosynthesis

This type of variation is rare in animals but abundant in plants, like seed colour, petal colour, etc.

Genetics: Organisms inherit a unique combination of alleles from their parents. Differences occur during (crossing over) meiosis Unless you are an identical twin, the chances of having the same alleles are slim. Hence, we have unique characteristics.

Environmental: Linked with genetics Over eating= obesity Plants- lack of water and minerals stunts growth Over exposure to sun= more melanin in skin (tan)

(d) outline the behavioural, physiological and anatomical (structural) adaptations of organisms to their environments;

Behavioural: An aspect of behaviour of an organism that helps it to survive (reptiles sunbathing to

increase body heat).Physiological/Biochemical:

An adaptation that ensures the cell processes are functioning (yeast produces enzymes that respire sugars that are present.

Anatomical: A structure that enhances the chances of survival of an organism (bacteria have

flagella to help them move by themselves)

(e) explain the consequences of the four observations made by Darwin in proposing his theory of natural selection; (HSW1)

Bell-shaped curve

Darwin observed that: Offspring appear genetically similar to their parents. No two individuals are identical. Organisms have the ability to produce large number of offspring.

This led to the conclusion that: There is a struggle to survive More offspring are produced than the habitat can sustain= more competition for food

and resources All individuals are different= some are more adapted than others Better adapted= get more food and resources= pass on their characteristics to their

offspring Less adapted= more likely to die before they reproduce Over time the number of changes will give rise to a new species

(f) define the term speciation; The formation of a new species.

(g) discuss the evidence supporting the theory of evolution, with reference to fossil, DNA and molecular evidence;

Fossils: Found to show similar organisms over a period of time. Slow changes and different environmental changes are shown. They have been compared to modern species, shows similarities.

DNA: Comparing genes by sequencing DNA bases. Most distantly related species show differences in DNA (evolution?)

Molecules: 2 closely related species will have similar biological molecules

(h) outline how variation, adaptation and selection are major components of evolution;

(j) discuss why the evolution of pesticide resistance in insects and drug resistance in microorganisms has implications for humans (HSW6a, 7c).

Insecticides applies a strong selective pressure Insects affected by this die Those who resist survive

The resistant insects:

Pass on resistance to next generation Therefore, whole population is resistant Insecticide is no longer effective

(Applies to antibiotics and bacteria too)

Module 2.3.4 Maintaining Biodiversity

(a) outline the reasons for the conservation of animal and plant species, with reference to economic, ecological, ethical and aesthetic reasons;

Economic reasons: Evolution= provides answers to technological questions (eg. best

aerodynamic shape in water).Ecological reasons:

Natural ecosystems provide processes valuable to humans: Without soil= no crops= no food Purification and retention of water (makes it safe to drink) Regulation of the atmosphere and climate Plants photosynthesise to remove CO2 and release O2

Ethical reasons: All living organisms have the right to survive and live in the way they have become

adapted on earth. Loss of habitat and biodiversity= organisms not living in natural habitat. Can lead to endangered species/extinction

Aesthetic reasons: Studies show that patients recover quicker from stress and injury when exposed to

pleasing natural environment conditions.

(b) 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; Domesticated plants have been bred to produce the best yield in specified conditions:

Change in climate (temperature)- plant unable to adapt Higher temperature= longer growth and breeding for pests Milder temperature= not cold enough to kill pests Plant produces less yield= not enough food produced Human diseases migrate= tropical diseases can become a problem Species who have lost their habitat will be unable to evolve and adapt to changes in

temperature and rain fall. Migration could lead to obstructions such as; humans, large amounts of water,

human development ect.

(c) explain the benefits for agriculture of maintaining the biodiversity of animal and plant species;

Agricultural crops have little diversity. As the climate changes they may longer be able to grow in their current location. Farmers could breed their agricultural plants with wild species that can grow in a new

climate. The offspring will have a high yield and be able to grow in warmer conditions. Specific resistant to disease could be bred to prevent extinction.

(d) 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;Conservation in situ- attempting to minimise human impact and to protect on the natural.

Types of conservation in situ- Conservation parks (natural parks), nature reserves ect.

Advantages: Cheap- as we only provide a supportive role Plants and animals conserved in natural environment Permanently protects biodiversity Permanently protects significant elements of natural and cultural heritage Facilitates scientific research

Disadvantages: Protected animals can come out to raid crops People continuing to hunt protected animals for food Illegal harvesting of timber and other plant products Tourists feeding protected animals or leaving litter

Conservation ex situ- conserving an endangered species outside its natural habitat

Types of conservation ex situ- Zoo’s, seed banks ect.

Advantages: Can enable repopulation of endangered species. Can enable repopulation in the wild. Animals are protected from predators

Disadvantages: Expensive Animals are not in natural habitat so fail to breed successfully. Space is limited so restricts genetic diversity. Low genetic diversity= lack of variation.

(e) 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;

Botanical gardens are involved in the conservation of endangered species.

Seeds banks hold a collective sample of seeds from different species of plants. They contain seeds that remain viable for years.There are many advantages that the seeds have to benefit humanity:

food builinding material disease-resistant crops (agricultural purposes) for habitat repopulation

(f) discuss the importance of international co-operation in species conservation with reference to The Convention in International Trade in Endangered Species

(CITES) and the Rio Convention on Biodiversity;

Loss of habitat and number of endangered species is a worldwide problem. International cooperation in conservation is essential for the benefits of both.CITES:Overall Aim- ensures that international trade in specimens of wildlife does not threaten their survival.CITES aims to:

Monitor and regulate international trade of specific plants and animals. Ensure international trade does not endanger the survival of a species. Ensure trade in wild plants is prohibited for commercial use.

Convention on biological diversity:Overall aim- Promoting sustainable development.Recognises that biological diversity is more than plants, animals, microorganisms and their ecosystem. Also about people and their secure need for food, medicines, fresh air and water.The aims of the convention are:

Conservation of biological diversity Sustainable use of its components Appropriate shared access to genetic recourses

Each member state must make ex situ conservations. So wildlife parks, zoo’s and seed bank facilities are found in the agreed governments.

(g) discuss the significance of environmental impact assessments (including biodiversity estimates) for local authority planning decisions;

Taking a EIA is to assess the likely significant effects that a proposed development may have on an area.

Reasons to carry this out: Avoid/minimise any significant effects on the biological diversity of an area. Any environmental consequences of development are taken to account.

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