GCSE Biology Revision Notes PDF

GCSE Biology Revision notes Paper 1 Contents Section 1 CELL BIOLOGY Part A Cell Structure....................................................................................................... 2 Section 1 CELL BIOLOGY Part B Cell Divisi...

GCSE Biology Revision notes Paper 1 Contents Section 1 CELL BIOLOGY Part A Cell Structure....................................................................................................... 2 Section 1 CELL BIOLOGY Part B Cell Division......................................................................................................... 6 Section 1 CELL BIOLOGY Part C Transport in Cells................................................................................................ 9 Section 2 ORGANISATION Part A – Digestion and enzymes................................................................................12 Section 3 INFECTION AND RESPONSE Part A Non-communicable diseases........................................................15 Section 3 INFECTION AND RESPONSE Part B Communicable diseases................................................................18 Section 3 INFECTION AND RESPONSE Part C Human Defence Systems...............................................................20 Section 3 INFECTION AND RESPONSE Part D Drugs and other treatments.........................................................21 1|Page Section 1 CELL BIOLOGY Part A Cell Structure Name the two groups of cells Prokaryotic and eukaryotic Prokaryotic cells info: Smaller, (just cell membrane, cytoplasm and cell wall – NO NUCLEUS) Genetic material not in a nucleus — single DNA loop May contain small circular DNA called plasmids Example of a prokaryote? cell membrane slime capsule* cell wall plasmids Bacteria Draw and label a bacterial cell: * not always present cytoplasm genetic material Flagella* Eukaryotic cells info: More complex, (cell membrane, cytoplasm — may or may not have a cell wall) HAVE A NUCLEUS Genetic information stored in a nucleus Examples of eukaryotic cells: Animal, plant, fungi and protista Sketch and label an animal and palisade (plant leaf cell) cell membrane cell membrane ribosomes ribosomes cell wall mitochondria mitochondria cytoplasm cytoplasm permanent vacuole nucleus chloroplast nucleus For each organelle state its function. (First 5 for both animal and plant cells): Ribosome: Protein synthesis Mitochondria: Site of aerobic respiration (release of energy) Nucleus: Controls cell activity — contains genetic material Cell membrane: Controls movement of substances in and out of cell Cytoplasm: Liquid gel where most of cell reactions happen (e.g. anaerobic respiration) What organelles are found in plant cells and what is their function? Cell wall — cellulose for strength (algae have too) Chloroplasts — contain chlorophyll for photosynthesis Vacuole — contains cell sap — keeps cell rigid Chloroplast/chlorophyll — what is the difference? Chloroplast is the organelle structure — chlorophyll is the green pigment that absorbs sunlight 2|Page  ____________________________________________________________________________________ As an organism develops... Cells differentiate to form specialised cells What is a specialised cell? A cell that has got different sub-cellular structure So its structure is linked to its function — specific to its job Examples of specialised cells in animals: 3 Nerve cells long axon to carry electrical impulses over long distances special ends that release chemicals to transfer messages to other nerves lots of mitochondria to release energy from respiration Muscle cells many mitochondria for high rate of respiration to contract stores of glycogen as energy source for respiration Sperm cells tail to swim towards egg mid-section has lots of mitochondria to release energy from respiration acrosome (head) has enzymes that breakdown egg layers to gain access Examples of specialised cells in plants: 3 Root hair cells have extensions (hairs) to increase SA for fast absorption of water/nutrients many mitochondria to provide energy for active transport of nutrients against conc gradient have thin cell walls to provide a short diffusion/osmosis distance Xylem long, hollow, dead, tube cells for fast movement of water up the plant cell walls strengthened with lignin Phloem special sieve holed walls to allow movement of dissolved substances no internal structure to obstruct flow When does cell differentiation occur? Animal at early embryo stage — plants retain the ability to differentiate throughout life In mature animals, what is most cell division for? Repair and replacement ____________________________________________________________________________________ Types of microscope: Light and electron Why is the electron microscope useful? To study cells in finer detail Advantages of electron microscope? Has bigger magnification and better resolution What is the difference? Resolution the ability to distinguish between two separate points which are close together Magnification = how many times bigger the object gets 3|Page The magnification equation: magnification (m) = image size (i) object size (o) Rearranged — use triangle if needed: image size = magnification x object size i object size = image size m x o magnification What is it very important to remember before using the equation? Getting all data in the same units How to convert: millimetres (mm) ÷ 1,000 x 1,000 micrometres (m) ÷ 1,000 x 1,000 nanometres (nm) REMEMBER – divide up! Labels of the light microscope Eyepiece lens coarse focus fine focus High power objective lens Low power objective lens Slide Stage Mirror What can we use to estimate size comparisons? Orders of magnitude Orders 1-3 10 times bigger = 101 bigger = 1 order bigger 100 times bigger = 102 bigger = 2 orders bigger 1000 times bigger = 103 bigger = 3 orders bigger How to work out how many times bigger objects are? Divide the bigger number by the smaller one — answer should be —10, —100, 1000 ____________________________________________________________________________________ 4|Page How do bacteria grow? Multiply by binary fission (simple cell division) very quickly (—20 mins) What do they need? Enough nutrients and suitable temperature How can we grow them in a lab? In nutrient broth or as colonies on agar plates Why do we need to grow bacteria? To investigate the effect of chemicals like disinfectants and antibiotics against microorganism What does contaminated culture mean'? The unwanted growth of microorganisms in bacteria culture which is pure How do we grow microbes in a school lab? (5) Use sterilised petri dish and agar Sterilise inoculating loop — pass through flame Use loop to transfer bacteria into agar media Seal lid to prevent contamination — store upside down Incubate at 25oC for 2 days Why left at 25oC in school? To reduce the risk of harmful pathogens growing How do you sterilise the equipment? Heat treat (autoclave) What about the microbes in the air? Always work close to a Bunsen burner — the heat will kill the microorganisms How to calculate cross sectional area? Surface area of a circle = πr2 How to calculate the number of bacteria in a population after a certain time? Step 1 — calculated how many times the bacteria can divide in the time Eg. Mean division time in 30 minutes, time allowed for division is 8 hours 8 hours = 480 minutes 480 ÷ 30 = 16 division in 8 hours Step 2 — calculate the number of bacteria in the end population using: number of bacteria at end = number of bacteria at start x 2number of divisions Eg. If the starting colony is 2, and has divided 16 times: Number of bacteria at the end = 2 x 216 = 2 x 65536 = 131072 All answers for HT biology maths must be given in... Standard form (see maths skill section) 5|Page Section 1 CELL BIOLOGY Part B Cell Division Genetics size rules: Cells contain nucleus, which contain chromosomes, which are made up of genes, which have a genetic code, made from the molecule DNA What are chromosomes? Structure of inheritance — made up of many genes What are genes? Section of DNA that codes for a particular trait What are alleles? Different versions of a particular gene — i.e. blue eyes or green eyes What is DNA? Deoxyribonucleic acid — the molecule of inheritance = the genetic code What shape is DNA? Double helix What is the genetic code use for? To combine amino acids in a specific order to make proteins such as enzymes In humans — how many chromosomes do cells have? Normal body cells 46 Gametes 23 What are gametes? The sex cells, sperm or egg Why do most organisms have an even number of chromosomes? The occur in pairs, one inherited from each parent The pairs are called? Homologous pairs – Two of each chromosome What does this mean? We have two copies of each gene ____________________________________________________________________________________ What is cell division? A cell splitting its nucleus and membrane to create new cells What are the two types? Mitosis and meiosis What is mitosis? The production of two genetically identical cells from an original cell which have the same number of chromosomes What is it important for? Growth, tissue repair and replacement What happens during mitosis divisions? DNA replicates and divides once. 6|Page What is the cell cycle? Stage 3 Series of stages that cause cells to divide Stage 2 Stages of the cell cycle: 1. Cell grows and makes more mitochondria and ribosomes, DNA replicates 2. One set of chromosomes moves to each end of cell, nucleus divides (mitosis) 3. Cytoplasm and cell membrane divides to form two genetically identical cells Stage 1 Describe the cells in mitosis and sketches: not dividing — no chromosomes visible chromosomes become visible chromosomes pulled to either end of the cell cell membrane and cytoplasm divide two genetically identical cells are formed ____________________________________________________________________________________ What are stem cells? Unspecialised cells that can differentiate into any specialised cell of an organism What is differentiation? Stem cells becoming specialised — being assigned a specific job 7|Page When does differentiation happen in animals? Mainly during early stages of development in womb What about in plants? They keep some stem cells even when mature in their meristem tissues (root and shoots) What can stem cells be used for in plants? Cloning plants — creating genetically identical plants for research, horticulture and agriculture Protecting rare species from extinction How? Take a small piece of leaf tissue, grown under right conditions by mitosis to create an unspecialised bundle of cells. Then split the cells and grow into identical plantlets. Human stem cells — sources: 1. embryonic stem cells — human embryos 2. adult stem cells — bone marrow Problem with adult stem cells? Keep some specialism and so cannot be made to differentiate into all types of cells but can turn into lots of cells including blood cells Human stem cells use? Cloned to differentiate into cells/tissues/organs for medical therapy Examples? Nerves cells — paralysis Pancreatic cells — diabetes Organs — e.g. kidney for transplant Heart cells — heart attack recovery How are these cells made? Embryo is produced with the same genes as the patient — this means that the cells/tissues/organs are not rejected by the patients' immune system. Evaluate use of stem cells for therapy Pros: reduce suffering by treating disease/ save NHS money/ no rejection issues Cons: expensive and not always effective/ ethical issue with discarding embryos/ possible transfer of viral infections Summary: the high cost spent researching a developing the treatment will be outweighed by saving to NHS once treatment is established so I think it's a good idea. 8|Page Section 1 CELL BIOLOGY Part C Transport in Cells What are the three ways substances can move? Diffusion, osmosis and active transport Why do substances need to move? Life processes need gases and other dissolved substances before they can happen E.g. (2) Respiration requires glucose and oxygen to be inside cells Photosynthesis requires carbon dioxide and water to get into the plant What is diffusion? (4) The movement of molecules from an area of high concentration to an area of low concentration Down the concentration gradient (high concentration to low concentration) Passive process — require no energy Occurs until equilibrium Examples of diffusion Oxygen from the air into the bloodstream C02 from the bloodstream into the air Oxygen into cells of body from the blood to supply respiration Carbon dioxide into actively photosynthesising cells What causes diffusion? Passive — no energy required: relies on molecules moving randomly due to the energy they have Factors that affect rate of diffusion (ROD) and what makes diffusion quicker (3) Difference in concentration – The larger the concentration gradient = faster ROD temperature/thermal energy – higher temperature = faster ROD Surface area – larger SA = faster ROD ____________________________________________________________________________________ What is osmosis? (4) The movement of water molecules from an area of high water concentration to an area of low water concentration through a selectively permeable membrane. Down the concentration gradient (high concentration to low concentration) Passive process — requires no energy Occurs until equilibrium A high concentration of water is AKA? Dilute solution A low concentration of water is AKA? Concentrated solution Osmosis in animal cells — what are the three types of solution? Hypotonic, isotonic and hypertonic Cells in a hypotonic solution? Concentration of solutes is lower than inside the cell so water moves in by osmosis and cell bursts Cells in an isotonic solution? Concentration of solutes is equal to inside the cell so no NET movement of water by osmosis and cell remains same size 9|Page Cells in a hypertonic solution? Concentration of solutes is higher than inside the cell so water moves out by osmosis and cell shrivels Importance of osmosis in plants To keep turgor of cell — vacuole fills with water and cell becomes hard and rigid If plant cell in hypertonic solution? Water leaves cell, and cell becomes flaccid (soft) Cell cell Eventually... (images) wall membrane Plasmolysis happens and cell membrane pulled away from the cell wall If water/ion balance not maintained what happens? Water moves in/out of cell by osmosis so cells do not work as efficiently— can die ____________________________________________________________________________________ What is active transport? (3) the movement of molecules from an area of low concentration to high concentration against the concentration gradient active process — requires energy Other than requiring energy, what is different about active transport? Use of a protein carrier to move substances Example of active transport use? (3) glucose from low concentration in small intestine into the blood glucose re-absorption in the kidney uptake of mineral ions in the root of plants Single celled organisms large SA:V ratio so easily exchange substances with the surrounding environment for their metabolic needs Problem with multicellular organisms? Small SA:V ratio so exchange (including diffusion) is difficult due to large number of cells How is problem overcome? (Exchange surface adaptations) Large surface areas — more space for exchange Thin walls — short diffusion path Increase concentration gradient by moving substances Examples of these adapted surface areas Lung alveoli, small intestine, villi, leaves, plant roots, fish gills Fish gill (can be inside or outside the fish) Extension flaps increase SA for gas exchange Good blood supply to increase conc gradient Counter current flow to increase exchange Exchange in the small intestine — adaptations (3) Lots of tiny extensions = microvilli increase SA for absorption of nutrients Each villus has a good blood supply to maintain concentration gradients Lots of mitochondria to provide the energy for active transport 10 | P a g e Surface area to volume ratio SA: V Small organisms have a large SA:V ratio Large organisms have a small SA:V ratio Maths to explain: E.g. small cube = 1x1x1 SA = 6 V = 1 SA:V = 6:1 Larger cube = 3x3x3 SA = 54 V=27 SA:V 54:27 = 2:1 So, as organisms get bigger their SA:V ratio get smaller What does it mean? That large organisms need organ systems in order to provide the large number of cells with sufficient exchange 11 | P a g e Section 2 ORGANISATION Part A – Digestion and enzymes What is the order of size rules? Cells → tissues → organs → organ systems → organisms What is a tissue? A group of cells with a similar structure and function Human tissues and function (roles specifically in the stomach) Muscular — contracts – churn food and digestive juices together Glandular — secretion of enzymes/hormones - produce digestive juices Epithelial — cover the body and organs - covers the inside and outside of stomach Plant tissues and function? (4) Epidermal — covers and protects Mesophyll — got lots of chloroplasts to carry out photosynthesis Xylem/phloem — transport of water and dissolved materials Meristem — growing tissue found at tips of roots and shoots — stem cells and high mitosis rate Mesophyll made up of... Palisade mesophyll and spongy mesophyll layers What is an organ? Many different types of tissues all working together for a function Plant organs and function (3) Roots — absorb water and minerals Stem — support leaves and flowers Leaves — photosynthesis Plant organ system Transport system — made up of root, stems and leaves When many organs work together it is called a... Organ system AQA organ system of choice and function? `Digestive system — to breakdown large insoluble molecules into smaller soluble ones that your body can then absorb The digestive system —you need to be able to label it with some functions: 12 | P a g e What is a protein? A large molecule made up of small units called amino acids Protein functions in the body? (4) Structural — muscles and tendons Hormones Antibodies Enzymes What is an enzyme? A biological catalyst What do enzymes do? (2) They speed up the rate of reactions without being used up themselves They build up small molecules into large one or breakdown large ones to small. How do they speed up reactions? By lowering the activation energy needed for a reaction to begin What does optimum mean? Conditions where enzymes work at their highest rate How do enzymes work? Lock and key theory — model to explain how enzyme active site bind specifically with their substrate because they have the same shape. What does denatured mean? Changing the specific shape of the enzyme protein so the active site no longer fits the substrate — no enzyme substrate complexes can be made What causes denaturing? Too high temperature Incorrect pH How to increase rate of enzyme reactions? Increase energy, increases collision, increases enzyme substrate complexes increased ROR Sketch graph, describe and explain how enzymes are affected by temperature Describe as temp increase, rate of reaction increases to a max value of *** at *** at temp goes up more, rate of reaction falls quickly Explain rate of reaction goes up initially as there is more kinetic energy= more collisions= more enzyme substrate complexes - max is enzymes optimum temp rate of reaction falls quickly as enzyme is denatured, change in specific shape of active site so no enzyme substrate complexes forms 13 | P a g e Sketch graph, describe and explain how enzymes are affected by pH Describe as pH increase, rate of reaction increases to a max value of *** at *** at pH goes up more, rate of reaction falls Explain — at high and low pH enzymes are denatured so no enzyme substrate complexes formed, active site changed specific shape and no longer fits substrate max rate of reaction is optimum pH for enzymes Remember for different enzymes... They have different optimum conditions different pH and temperature they work best at Calculating rate how much product is made Rate = how long it took to make ____________________________________________________________________________________ What is an extracellular enzyme? Plus example One that works outside of cells — digestive enzymes What is the function of these digestive enzymes? To breakdown large insoluble molecules into small soluble ones which can be absorbed into the blood Draw the enzymes memory table: Large insoluble molecule Name Where acts and is made Produces... eaten Carbohydrates carbohydrase Mouth glucose Proteins Protease Stomach Amino acids Fats Lipase Small intestine fatty acids and glycerol All enzymes also made in the... Pancreas What conditions are the stomach? Acidic — hydrochloric acid (HCI) What is the role of bile? (2) Neutralise acid from stomach - for lipase enzymes in optimum conditions Emulsifies fats to create a larger surface area for lipase to break them down Bile info... Made in the liver, stored in the gall bladder Amylase A special carbohydrase which breaks down starch into simple sugars in the mouth and sml intestine What is metabolism? The sum of all the reactions in a cell or body 14 | P a g e What are the products of digestion used for? To build new carbohydrates, lipids and proteins. Glucose is used for respiration Practical food tests and positive results Test for starch iodine — positive result yellow/red to blue/black Test for sugars benedict's solution — positive result = blue to brick red (heat) Test for protein = Buiret reagent — positive result = blue to purple Test for fats = ethanol — positive result = clear to cloudy Safety to consider. Ethanol = flammable, Buiret corrosive ____________________________________________________________________________________ Section 3 INFECTION AND RESPONSE Part A Non-communicable diseases What is health? A state of physical and mental well-being What are the two types of disease? Communicable and non-communicable What is the difference? Communicable disease is infectious Other than communicable and non-communicable disease, what can make us ill? Diet — overeating = risk of type 2 diabetes Stress — linked to heart disease/cancers Life situations — where you live = access to medicine Examples of non-communicable disease? Coronary heart disease, stroke, COPD (chronic obstructive pulmonary disease) A non-communicable disease... Cannot be passed on from one person to another What contributes to non-communicable disease? Risk factors — aspects of a person's lifestyle, or substance present in the body/environment that have been shown to be linked to an increased rate of disease Most diseases? Are caused by the interaction of a number of factors what is a causal relationship? For some non-communicable diseases have been proved that a certain risk causes the disease If there is no causal relationship, what do we describe the increase risk as? A correlation — as risk factor increases, so does disease HOWEVER... correlation is not causation, another factor may be involved eg genetics How can different types of disease interact? 3 examples: Defects in the immune system means you are more likely to suffer an infection disease Viruses living in cells can be triggers for cancer (eg HPV — cervical cancer) Immune reaction caused by a pathogen can trigger allergies (asthma/rashes) What are the known risk factors for disease? 15 | P a g e  The effects of diet, smoking and exercise on cardiovascular disease. Obesity as a risk factor for Type 2 diabetes. The effect of alcohol on the liver and brain function. The effect of smoking on lung disease and lung cancer. The effects of smoking and alcohol on unborn babies. Carcinogens, including ionising radiation, as risk factors in cancer. What do you need to be aware of in terms of effects of non-communicable diseases? The human cost (deaths) the financial cost (treatment) for an individual, community, nation or globally Explain the effect of poor diet? a poor diet increases your risk of developing cardiovascular disease directly through cholesterol levels causing CAD and indirectly through obesity (body stress of being overweight) what is the effect of exercise? Reduces the likelihood of developing cardiovascular disease Obesity is a strong risk factor for? Type 2 diabetes Explain the effect of high alcohol consumption? Alcohol is toxic and damages the liver causes cirrhosis and liver cancer — it also causes brain damage and can affect unborn babies’ development. Explain the effect of smoking Smoking causes cardiovascular disease including coronary heart disease, lung cancer and COPD If a foetus is exposed to smoke? Has restricted oxygen levels and carbon monoxide takes the place of oxygen in red blood cells, this leads to low birth weight, premature birth and even stillbirth. ____________________________________________________________________________________ 4.2.2.7 Cancer What is cancer? A change in cells that lead to uncontrolled cell growth and division. Uncontrolled cell growth can cause cancers to grow very large. What changes in a cancer cell? The DNA in the nucleus. This change is called a mutation. What are the two types of tumours? Benign tumours and Malignant tumours Features of Benign tumours Growths of abnormal cells which are contained in one area, usually within a membrane. They do not invade other parts of the body. Features of Malignant tumours Generally referred to as cancers. Some of the cancer cells split off and travel to different parts of the body in the blood They settle in different organs and form secondary tumours. Lifestyle risk factors for various types of cancer. 16 | P a g e  Smoking – lung cancer UV – skin cancer Viruses (e.g. HPV) – Cervical cancer Alcohol – liver cancer There are also genetic risk factors for some cancer o E.g. Breast cancer Why has the survival rates for all cancers increased? Improved treatment / drugs Earlier diagnosis More cancer screening Improved patient knowledge (of risk factors) 17 | P a g e Section 3 INFECTION AND RESPONSE Part B Communicable diseases What is a pathogen? A micro-organism that causes infectious disease Name the pathogens we need to know Bacteria, viruses, protists and fungi How are they different to animal and plant cells? Much smaller What do they infect? Plants or animals What does infectious mean? Disease that can be passed between people How can pathogens be transmitted? Plus example Air - Droplet infection (cough or sneeze) Direct contact (STIs) Contaminated food/drink (salmonella) How can we prevent spread of disease? (4) Simple hygiene measures Destroying vectors Isolation of infected individuals Vaccination How do bacteria make us feel ill? (2) Reproduce quickly produce toxins which damage tissues How do viruses make us feel ill? (3) Reproduce quickly, live and reproduce inside cells causing cell damage Do pathogens make us feel ill straight away? No — they must reproduce to high numbers to make enough toxin to make us feel ill ____________________________________________________________________________________ Viral Diseases Viral diseases = Measles, HIV and TMV Measles info Symptoms — fever and red skin rash (can be fatal) Spread — droplet infection from sneezes Prevented — isolate patient / vaccination HIV info Symptoms Initially flu like Late stage — AIDS immune system so damaged it can no longer fight infection Spread — sexual contact or exchange of bodily fluids (eg share needles) Prevented — safe sex, not sharing needles Treatment- antiretroviral drugs 18 | P a g e TMV info Tobacco mosaic model — plant pathogen eg tomatoes Symptoms — mosaic discoloration of leaves affecting growth due to lack of photosynthesis Spread — contact and vectors Prevented — field hygiene and pest control ____________________________________________________________________________________ Bacterial Diseases Bacterial Diseases = Salmonella and Gononhoea Salmonella info — Symptoms — fever, abdominal pain and diarrhoea Spread — bacteria ingested in food prepared in unhygienic conditions Prevented — poultry vaccinated — good food hygiene Gonorrhoea info — Symptoms — yellow/green discharge from vagina or penis/ pain urinating Spread — STI sexually transmitted disease Prevented — barrier method of contraception e.g. condom Treated — antibiotics Issue with antibiotic use for gonorrhoea? Many strains are becoming resistant to penicillin ____________________________________________________________________________________ Fungal Diseases Fungal diseases = Rose black spot Symptoms — purple/black spots on leaves, turning yellow and drop off early affecting growth as photosynthesis is reduced. Spread — water and wind Prevention — removing/ destroying affected leaves Treatment — fungicides ____________________________________________________________________________________ Protist Diseases What is a protist? Single celled organisms What is a parasite? Live and feed on another organism Example of a disease caused by a parasitic protist: Malaria Malaria info: Symptoms — repeated fevers Spread — live as a vector in the female mosquito, infected when bitten Prevention — preventing mosquito breeding/ using mosquito nets/avoid being bitten ____________________________________________________________________________________ 19 | P a g e Section 3 INFECTION AND RESPONSE Part C Human Defence Systems What is a pathogen? Microbe which causes disease How can the body defend itself from pathogens? Non-specific/passive methods Specific immune response Name 5 of the body 's passive defence mechanisms: Protective barrier skin — physical barrier Nose hairs — mucus coated trap microbes to protect lungs Trachea and bronchi Stomach acid Clotting of blood — prevent entry of microbes How do the trachea and bronchi protect our bodies? Ciliated cells sweep mucus made by goblet cells. Mucus traps microbes and is moved up to the throat to be swallowed into the stomach. How does stomach acid help? Hydrochloric acid (HCI) which kill most microbes in our food and mucus from lungs. If a microbe gains entry to the body? The immune system tries to destroy the pathogen What is the name of the cell which helps us defend against pathogens? The white blood cells How does the white blood cell protect us? (3) they ingest pathogens — digest and destroy they produce antibodies - destroy specific pathogen they produce antitoxins to neutralise toxins pathogens produce What is the 'science ' name of ingestion of microbes? Phagocytosis ____________________________________________________________________________________ Vaccination How does a vaccine/ immunisation work? (4) inject dead or inactive form of disease stimulates antibody production by white blood cells which can rapidly produce correct antibodies on re-infection How do vaccinations help? Prevent illness of the individual Prevent spread of pathogens How do vaccinations prevent spread? Immunising a large enough proportion of the population that infected individuals do not come into contact with people who are not vaccinated so infection doesn't spread. 20 | P a g e WS 1.4 Evaluate the global use of vaccination in the prevention of disease... Vaccination has massively reduced the number of deaths and spread for certain diseases. Pros — reduced deaths and spread of disease Cons — access for all and cost of immunising programmes Cons summary — overall, I think that even though vaccinations can be expensive, they have massively reduced deaths due to certain diseases. ____________________________________________________________________________________ Section 3 INFECTION AND RESPONSE Part D Drugs and other treatments Antibiotics and Painkiller How do you treat bacterial infections? (plus example) Antibiotics eg penicillin How do they work? Cure bacterial disease by killing ineffective bacteria inside the body What is important about treating with antibiotics? Specific bacteria should be treated by specific antibiotics Who discovered antibiotics? Fleming at first but other scientists developed and tested on people Antibiotics good? Greatly reduced deaths from infectious bacterial diseases Antibiotics bad? Using them has led to the emergence of strains resistant to antibiotics — massive concern What can antibiotics not kill? Viral infections It is difficult to kill viruses without what effect? Damaging body tissues why are viral infection hard to treat? viruses live inside cells viruses inaccessible to drugs drugs would damage body cells viruses mutate frequently What is antibiotic resistance? When bacteria mutate to that they can no longer be treated by a specific antibiotic What has caused this? Inappropriate and overuse of antibiotics What do painkillers do? Relieve symptoms (stop pain) but do not kill the pathogen that causes disease What is a mutation? Change in DNA sequence which could give a new characteristic that can be good, bad or indifferent. 21 | P a g e How has resistance developed? Through natural selection — when a new characteristic is beneficial, the organisms survives HT ext: how does natural selection lead to resistance? Antibiotics kill individual pathogens of non-resistance Individual resistant pathogens survive and reproduce proportion in a population that are resistant increases HT ext: what is happening more recently? Antibiotic not used to treat non-serious infections to rate of new resistant strains developing has slowed down. How can we fight against resistance strains? Continually develop new antibiotics What is the problem with these resistant strains? Spread quickly through communities/hospitals as there is reduced treatment. Example of resistant strain MRSA or SARS What is an epidemic? Countrywide spread of disease What is a pandemic? Worldwide spread of disease ____________________________________________________________________________________ Discovery and Development of Drugs Where have drugs traditionally from? Extracted from plants and microorganisms For example? Heart drug digitalis originated from foxgloves Painkiller aspirin originated from willow Antibiotic penicillin from Penicillium mould Most new drugs... Are synthesised by chemists in the pharmaceutical industry However... ? The starting point may still be a chemical extracted from a plant New medical drugs must be? Tested and trialled before being used What are the two main stages of drug development for new medicines? Preclinical and clinical trials What do we test drugs for? Toxicity — is it safe? Efficacy — is it effective? Dose — how much should we take? Preclinical testing? Done in laboratory using cells, tissues and live animals 22 | P a g e Clinical trials? Healthy volunteers given very low doses are given to see if it is safe Further trials with patients to see if the drug work and to find optimum dose Why are they given to healthy volunteers first? They are 'well' and so any bad side effects will have less of an effect What is double blind testing? Some patients given the drug; others given a placebo What is a placebo? Fake drug — no active ingredients What does double blind testing show? How effective the drug is compared to placebo effect What is placebo effect? A psychological effect where patients believe they will improve and so they do Results of testing and trials? Are published in scientific journals only after scrutiny by peer review ____________________________________________________________________________________ 4.3.2 Monoclonal Antibodies - Biology only What are monoclonal antibodies? Identical antibodies made from a single clone of cells What do they do? They are specific to one binding site on one protein antigen and so are able to target a specific chemical or specific cells in the body What can they be used for? Identification of substances How are they produced? Stimulating mouse lymphocytes to make a particular antibody. The lymphocytes are combines with a particular kind of tumour cell to make a cell called a hybridoma. What can this hybridoma cell do? The hybridoma cell can both divide and make the antibody Single hybridoma then are? Cloned to produce many identical cells that all produce the same antibody. Large amounts of the antibody can be collected and purified How can these antibodies be used? for diagnosis such as in pregnancy tests in laboratories to measure the levels of hormones and other chemicals in blood, or to detect pathogens In research to locate or identify specific molecules in a cell or tissue by binding to them with a fluorescent dye to treat some diseases e.g. for cancer 23 | P a g e How are antibodies used to treat cancer? the monoclonal antibody can be bound to a radioactive substance, a toxic drug or a chemical which stops cells growing and dividing. It delivers the substance to the cancer cells without harming other cells in the body. What is a negative of monoclonal antibodies? They create more side effects than expected and so are not as widely used as everyone hoped when first developed WS 1.3 evaluate the use of monoclonal antibodies Define — monoclonal antibodies are identical antibodies made from the same cloned cells. Pro — they can be used in treatment of diseases like targeting drugs to cancer cells - they can be used to measure levels of hormones in the blood Con — they Create more side effects than expected Cons sum — overall, I think that, even though the possibility to disease treatment is an advantage, because of the side effects created more studies should be done before wide scale use. 24 | P a g e