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As ocr biology revision pack unit f212 edited As ocr biology revision pack unit f212 edited Document Transcript

  • Emily Summers AS Unit F212: Molecules, biodiversity, food and health Module 1 - Biological molecules Biological moleculesDescribe 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 Glycine1
  • Emily SummersDescribe, with the aid of diagrams, the formation and breakage of peptide bonds in the synthesis and hydrolysis of dipeptides andpolypeptides. 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 structurewith reference to hydrogen bonding.Explain, with the aid of diagrams, the term tertiary structure, withreference to hydrophobic and hydrophilic interactions, disulphidebonds and ionic interactionsIonic Interactions weak attractionsbetween oppositely charged parts themoleculeDisulfide Bonds  Two molecules of anamino acid close together, the sulphuratoms in them bond together forming thisbond. (E.g. Cysteine)2
  • Emily SummersHydrophobic Water repelling groups near together in a protein they clump.Hydrophilic Water attracting groups are likely to be pushed outside, affecting theprotein’s final structure.Explain, with the aid of diagrams, the term quaternary structure, with referenceto the structure of haemoglobin.The quaternary structure tends to be determined bythe tertiary, when it involves multiple polypeptides.E.g. Haemoglobin has a quaternary structure, it has4 polypeptide chains.Describe, with the aid of diagrams, the structure of a collagen moleculeCollagen is a strong protein that is fibrous. It is asupportive tissue in animals; it is made of threepolypeptide chains that are very tightly coiled into atriple helix, interlinked by covalent bonds. Mineralsare 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 appearanceCompare the structure and function of haemoglobin (as an example of a globular protein) and collagen (as an example of a fibrousprotein). Haemoglobin CollagenGlobular protein Fibrous ProteinLarge variety of amino acids in it’s primary 35% of primary structure is glycinestructureHas a prosthetic group- haem Doesn’t contain a prosthetic groupMostly wound into alpha helix structures Mostly left handed helix structuresDescribe, 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.3
  • Emily SummersState 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 CelluloseLarge molecules of many alpha glucose Large molecules of many beta glucosemolecules joined with condensation molecules joined with condensationreactions, insoluble in water and form reactions, they are insoluble in water andgranules also strongFor energy storage in plants Structural found in plants where it forms cell walls4
  • Emily SummersDescribe, 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 livingorganisms.Carbohydrate Example Characteristics Function in OrganismsMonosaccharide Glucose (6 Carbon Small, soluble, sweet, Energy via respirationmonomers sugar) crystalline Deoxyribose (5 Part of DNA Carbon sugar) information moleculeDisaccharide dimers Maltose (2 glucoses) Small, soluble, sweet Sugar obtained when & crystalline starch is broken down in hydrolysis, can be split to glucose for more respirationPolysaccharide Starch & glycogen Large molecules, Energy store in plantspolymers 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.5
  • Emily SummersCompare, with the aid of diagrams, the structure of a triglyceride and a phospholipid.Phospholipid Phospholipids are similar to triglycerides except that one ofTriglyceride 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 thehydrocarbon tails of the fatty acids have lots of chemical energy that is released whenbroken down, so lipids contain double the energy carbohydrates do.They are insoluble because of their hydrophobic so they do not interfere with the waterpotential in cells that would cause water to enter cells by osmosis so they couldswell/burst.Phospholipid molecules have a hydrophilic head and a hydrophobic tail. The head facesoutwards and the tail faces inwards in the phospholipid bilayer on cell surfacemembranes, making it difficult for water soluble substances like Na+ ions and glucose topass through.6
  • Emily SummersCholesterol is a lipid found in cell membranes for mechanical stability, and is used tomake steroids. It has a hydrocarbon ring structure attached to a hydrocarbon tail. Thehydrocarbon 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 TestAdd Benedict’s solution to the substance and heat to 80 degrees Celsius in a waterbath. If the solution changes colour from blue to green-brick red then it is a reducingsugar. (Monosaccharide and disaccharide) Non reducing sugars do not react with Benedict’s solution so there would be no colourchange E.g. Sucrose, formed by a condensation reaction between glucose andfructose. The formation of this bond is different to reducing sugars, so it must be boiledwith hydrochloric acid, to hydrolyse/split the sucrose molecules to give glucose andfructose 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.StarchAdd iodine in a potassium iodide solution to the sample, and if there is starch thesample solution will change from yellow/brown to a dark blue/black. Negative resultspresent no colour change.LipidsMix the sample with ethanol, dissolving lipids present. Pour the solution into water in aseparate test tube. If there is a lipid there will be a cloudy white milky emulsion near thetop of the water.7
  • Emily SummersProteinAdd biuret reagent to a sample. The reagent contains sodium hydroxide and coppersulphate, reacting with the peptide bonds in protein turning the solution to a purplecolour 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 concentratedthe 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.8
  • Emily Summers Nucleic AcidsState that deoxyribonucleic acid (DNA) is a polynucleotide, usually double-stranded, made up of nucleotides containing the basesadenine (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).9
  • Emily SummersDescribe, with the aid of diagrams, how hydrogen bonding between complementary base pairs (A-T, G-C) on two anti-parallel DNApolynucleotides 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 ormore specific polypeptides.10
  • Emily SummersOutline 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 theamino 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, atemplate strand that is a copy of the coding strand of the double helixRibosomal RNA  In ribosomesTransfer RNA  Carries amino acids to the ribosomes and they are bonded together toform polypeptides. EnzymesState that enzymes are globular proteins, with a specific tertiary structure, which catalyse metabolic reactions in living organisms.Enzymes are:Globular proteins and soluble in waterAble to break molecules down or build them up!Biological catalystsSpecific- because they catalyse a reaction with only one type of substrateTheir globular structure has a pocket called an active siteActivity affected by temperature and pH (Rate of reaction)Enzymes are large molecules with hundreds of amino acids. A lot of these amino acidswork to keep the specific tertiary structure of the enzyme. The function of the enzymedepends on the shape, and for the enzyme to work correctly the tertiary structure mustbe maintained specifically.All of the structures (primary, secondary, tertiary) of the enzyme is involved in thespecific 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 donot produce unwanted by products.An individual cell could contain over one thousand enzymes to catalyse every process,like digestion, respiration, photosynthesis.11
  • Emily SummersState that enzyme action may be intracellular or extracellular.Extracellular Enzymes catalase reactions outside of the cellIntracellular Enzymes catalase reactions inside of the cellMould 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 quicklyat 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.12
  • Emily SummersDescribe and explain the effects of pH, temperature, enzyme concentration and substrate concentration on enzyme activity.pHpH is the measure of the H+ ion concentration. These ions are positive so they areattracted to negatively charged ions, or parts of molecules and repelled by positiveparts. Hydrogen bonds and ionic bonds hold the tertiary structure of an enzyme in placeso the active site is maintained in it’s correct shape. The bonds are there because ofelectrostatic attraction between opposite charges on the amino acids making up theenzyme.Hydrogen ions interfere with these bonds and can alter the tertiary structure of anenzyme by altering their concentration.Enzymes have their own optimum pH, the H+ ion concentration gives the enzyme thebest overall shape. Enzymes work in a narrow pH range usually, and their pH rangeoften changes with their location. E.g. Pepsin is in the stomach and has an optimum pHof 2. Handy! Whereas Trypsin has an optimum pH of 7 which is good for the conditionsof 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.13
  • 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.ConcentrationIncreasing the enzyme concentration increases rate of reaction to a point, until it will notincrease anymore because substrate concentration is the limiting factor. Reactionscannot be quick if there isn’t enough substrate left, and vice versa.14
  • Emily SummersDescribe how the effects of pH, temperature, enzyme concentration and substrate concentration on enzyme activity can beinvestigated experimentally.Variable Method of Keeping Reasons ConstantTemperature 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 foundEnzyme 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 areaSubstrate Concentration Accurately measured Rate of reaction depends substrate volume/mass on substrate molecule concentrationpH 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 enzymeExplain the effects of competitive and non-competitive inhibitors on the rate of enzyme-controlled reactions, with reference to bothreversible and non-reversible inhibitors.Competitive inhibitors have a similar shape to the substrate so they occupy the activesite and form an enzyme inhibitor complex but no product is made. So the enzymecannot catalyse a reaction and rate of reaction slows down. Depends on inhibitor andsubstrate 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 onthe enzyme to distort the tertiary structure of the enzyme. So the active site changes15
  • Emily Summersand the substrate can’t fit anymore, so no reaction can be catalysed and reaction ratedecreases. Increasing substrate concentration has no effect.Reversible inhibitors are when the inhibitor isn’t there permanently and afterwards theenzyme is unaffected.Non Reversible inhibitors are usually non competitive and the enzyme is denatured.Explain the importance of cofactors and coenzymes in enzyme-controlled reactionsCoenzymes take part in the reaction and are changed, but are recycled back to takeplace in the next reaction.Cofactors are there to ensure an enzyme controlled reaction takes place at anappropriate 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-activatingenzymes. For instance, Potassium Cyanide inhibits respiration of cells, because it is anon competitive inhibitor for a vital respiratory enzyme, cytochrome oxidase, in themitochondria. When cytochrome oxidase is inhibited the use of oxygen is reducedand 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 stopviruses from replicating by inhibiting the activity of protease- which are vital to viruses tobuild their new virus coats. Usually these inhibitors are competitive.Cystic Fibrosis sufferers have the problem that the passage of digestive enzymes thatare usually secreted from the pancreas into the gut is blocked, leading to digestiveproblems. Enzymes in a tablet can overcome the problem; they are in an acidresistant coat so they’re not destructed by acid/protein digesting enzymes located inthe stomach.Module 2 Food and HealthDiet and Food ProductionDefine the term “Balanced Diet”A diet that contains all the nutrients needed for health in appropriate portions16
  • Emily SummersExplain 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 of30 or over, with 20% or more above the recommended weight for your height, If youconsume too little or too much of each food group.BMI = mass in kg/ height in m2Discuss 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 +, causinghypertension, which is a too high blood pressure especially at diastolic pressure whenthe heart should be relaxing with a lower BP. This can damage the arteries inner liningwhich 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. Concentrationof cholesterol in blood shouldn’t exceed 5.2 mmol dm-3Discuss the possible effects of a high blood cholesterol level on the heart and circulatory system, with reference to high densitylipoproteins (HDL) and low density lipoproteins (LDL).HDL’s are made by unsaturated fats, cholesterol and protein. They carry cholesterolfrom the body tissues to the liver usually. The cells in the liver have receptor sites thatlet the HDL’s bind onto their cell surface membranes. In the liver the cholesterol is usedin cell metabolism to make bile or it can be broken down so high levels of HDL’s arelinked with reducing blood cholesterol levels.This is because they decrease fatty deposition in the artery walls caused byatherosclerosis and can even help to remove depositions of it. HDL’s use unsaturatedfats, 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 surfacemembranes.If there is too much saturated fat and cholesterol is consumed in the person’s diet thenthe blood concentration of low density lipoproteins will increase.17
  • Emily SummersDifferent 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. Theychange energy from the sun to energy in a chemical form that animals can use. So wedepend 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 monitoredFarmers breed cattle for a high milk yield and for meat production, dairy cows canproduce a massive 40l or more milk a day.Chickens are bred to produce eggs, or for meat. Egg layers can produce a huge 300 ormore 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 wereremoved 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. Animalsare 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 farmedclose to each other. Otherwise the diseases can reduce growth and reproduction.18
  • Emily SummersDescribe the advantages and disadvantages of using microorganisms to make food for human consumption.Advantages DisadvantagesProduction of protein can be faster than People don’t want to eat fungal protein orplant/animal protein food grown on wasteProduction can be increased/decreased Isolation of the protein is hard consideringeasily with demand the microorganisms are grown in big fermenters and need to be isolated from the material on which they growNo animal welfare issues The protein must be purified to ensure it isn’t contaminatedGood protein source for vegetarians e.g. The conditions needed to grow theseQuorn microorganisms are ideal for pathogens, which can cause infectionNo animal fat or cholesterol in protein The protein will not have the same taste/texture as traditional protein sourcesSCP production can be combined withwaste removalOutline the methods that 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 microorganismsDrying/salting/sugar coating Dehydrates microorganisms so water leaves them by osmosisSmoking Food has a hardened and dry outer surface and the smoke has antibacterial chemicalsPickling An acid pH kills microorganisms by denaturing enzymes and proteinsIrradiation Ionising radiation kills microorganisms by distorting their DNA structureCooling/freezing Slows metabolic processes and growth, reproduction by slowing down enzyme activity. Does not kill them.Canning Food is heated and sealed in airtight cansVacuum packing No air so microbes can’t respire aerobically19
  • Emily SummersHealth and diseaseDiscuss what are meant by the terms health and diseaseHealth is a complete state of physical, mental and social well being as well as theabsence of disease or infirmity.Disease is a departure from full health caused by a malfunction of the mind or bodyDefine 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 thehost. External head lice Internal TapewormPathogen A general term for any organism that causes diseaseBacteria, fungi, viruses, protoctistaDescribe the causes and means of transmission of malaria, AIDS/HIV and TB.Malaria is caused by a eukaryotic organism, from the genus Plasmodium and mostcommonly the species Plasmodium falciparum.Malaria is spread by means of a vector. The female Anopheles mosquito carries theplasmodium from an uninfected to an infected person, they feed on blood with adaptedmouthparts to penetrate a blood vessel and withdraw blood, malarial parasites live inthe erythrocytes of humans and feed on Hb.HIV/AIDSThe virus enters the body and is un-active, but once the virus is active andattacks/destroys T helper cells in the immune system your ability to resist infection isgreatly decreased. You are open to opportunistic infections which will eventually kill theperson 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 feedingTBTB 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 theimmune system controls it, it is transmitted by a droplet infection. Overcrowding20
  • 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 diseaseMalaria kills three million a year, but is limited to where the Anopheles can survivewhich 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 subSaharan Africa.TB Worldwide disease, new strains of Mycobacterium are resistant to drugs availableto 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 oflymphocytes 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 theirimportance. 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.21
  • 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 enzymesEyes are protected by tear fluid antibodies and enzymesEar canals are lined with wax to trap pathgogensDescribe, with the aid of diagrams and photographs, the structure and mode of action of phagocytes.22
  • Emily SummersDescribe, with the aid of diagrams, the structure of antibodiesOutline 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 cell23
  • Emily SummersA large antibody can bind lots of pathogens together so the group of pathogens are toolarge to enter a host cell.Compare and contrast the primary and secondary immune responsesCompare and contrast active, passive, natural and artificial immunity.Active Immunity Artificial ImmunityExposure to antigen No exposure to antigenProtection development takes a longer Protection is instantperiodProtection lasts a long while Protection lasts a short periodMemory cells made No memory cells made24
  • Emily Summers Active Immunity Passive ImmunityNatural Catch the disease Antibodies from mother to baby across placentaArtificial Vaccination Injected with antibodiesModule 3 Biodiversity & EvolutionBiodiversityDefine the terms species, habitat and biodiversityA species is a group of similar individual organisms with similar appearance,biochemistry, physiology and genetics whose members are able to interbreed freely toproduce fertile offspringA habitat is a place where the organism livesBiodiversity is the variety of life, the range of living organisms to be foundUse 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 = 11There are three of the red species, five of the white and three of the blueD = 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 indicateshigh biodiversity in a habit which is beneficial, a low one indicates low biodiversity in ahabitat which isn’t so good, and may suggest that conservation methods might have tobe put in place.ClassificationDefine the terms classification, phylogeny and taxonomy.25
  • Emily SummersClassification is arranging organisms into groups based on similarities and differencesin appearance.Phylogeny is the study of the evolutionary history of groups of organismsTaxonomy 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.26
  • 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.27
  • 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.28
  • Emily SummersEvolution 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 characteristicsfound in plants, animals and microorganisms.Continuous variation  Variation in which there is a full range of intermediatephenotypes between two extremesDiscontinuous variation  Variation in which there are discrete groups of phenotypeswith few or no individuals in between 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 Controlled by few/one gene (monogenic)(polygenic)No distinct categories Distinct categoriesLike heart rate, muscle efficiency, IQ, growth This type of variation is rare in animalsrate, rate of photosynthesis but abundant in plants, like seed colour, petal colour, etc.29
  • 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’sOutline 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 its 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 its 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.30
  • Emily SummersExplain 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 frompredation, disease and competition.Populations have constant sizes“Darwin concluded that individuals that were better adapted to their environmentcompete better than the others, survive longer and reproduce more, so passing on moreof their successful characteristics to the next generation. Darwin used the memorablephrases survival of the fittest, struggle for existence and natural selection.” Biology MadDefine the term speciation.Formation of a new species from the evolution of one speciesgeographical isolation which is an example of allopatric speciationreproductive isolation which is an example of sympatric speciationDiscuss 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 planningdecisions31
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