The Search For Better HealthBiology 1.1 Discuss the difficulties of defining the terms health and diseaseHealth is more than merely the absence of disease. Health is defined by the World Health Organisation (WHO) as a state of complete physical, mental and social well-being, and not merely the absence of disease or infirmity. This definition allows the whole person to be taken into account rather than just whether they have a disease or not. An individual who does not have a disease may still not be considered healthy. On the other hand, a person who suffers from a disease could still be classified as healthy.Physical health refers to the physical state of the body and includes things like our level of fitness, body weight, amount of energy and the proper functioning of the systems in the body. Mental health is related to our ability to function effectively in society and to cope with changing situations in our lives. Social health is our ability to interact, communicate and socialise effectively. One problem with the WHO definition is that it is very broad, and if taken literally, it would be very difficult to achieve a healthy status. It would be very unlikely that a person has a complete state of physical, mental and social well-being at any one time.The concept of health for individuals is very subjective on their lifes circumstances. What is healthy for one may not be regarded as healthy for another person. A person who is physically fit and not suffering from any disease would consider themselves to be healthy whereas a person who has a disability or a chronic disease, may describe themselves as healthy because they have learnt to adapt and cope with this disability or disease in their everyday life.Health is a constantly changing state and is relative to others and ourselves over a period of time.Disease can be defined in many ways, but one of the most common is any condition that adversely effects the normal functioning of any part of a living thing.This definition is also quite broad and the problem with this is that conditions that would not normally be classified as a disease would be included if this definition if it were taken literally. It could mean that a broken arm would be classed as a disease because it adversely affects the normal functioning of the body. Similarly, pregnancy could be classified as a disease.The normal function referred to in the definition may be at different levels for different individuals. E.g. Absent mindedness in the elderly may be a normal facet of aging whereas it could be the manifestation of a disease in the young. Another issue in defining health and disease is the ways in which the words are used. These terms used in every day conversations by the general public will have different meanings to the scientific definitions.

1.2 Outline how the function of genes, mitosis, cell differentiation and specialisation assist in the maintenance of healthThe maintenance of health is dependent on the information stored in the DNA of each cell. A gene is a hereditary unit that controls the production of polypeptides that make up the proteins in the cell. These proteins are responsible for normal cell functioning, growth and repair. A malfunction in a particular gene may result in the inability of the cells to function properly and lead to the onset of disease. For example, cystic fibrosis is a genetic disease that is caused by a mutation to the CFTR gene.DNA Repair genes code for proteins that are responsible for the stopping pf the cell cycle while other proteins remove the damaged regions of DNA and replace them with a new correct sequence. Proto-oncogenes code for proteins that stimulate cell growth and mitosis. Mutations to this gene lead to the expression of oncogenes that would normally be silent. This causes the uncontrolled production of cells and prevents cell death.Tumour suppressor genes code for proteins that slow down or stop cell growth and mitosis. These genes also code for proteins that induce cell death if there is an uncontrolled increase in cell numbers. Mitosis is the process of cell division by which identical body cells are produced to allow for growth; repair of damaged tissue, replacement of worn out cells; and genetic stability in which there is a precise and equal distribution of chromosomes to each daughter nucleus, so that all resulting cells contain the same number and kind of chromosomes as each other and the parent cell.This allows all cells to function normally and tissues in the body to be repaired and maintained. If cells are damaged through disease, they are replaced by the division of healthy cells close to the injury or disease site.

3.1 Describe the contribution of Pasteur and Koch to our understanding of infectious diseases Prior to the work of Pasteur, Koch and others, the theory of spontaneous generation was the accepted explanation for disease and decay. This theory involved the idea that life (such as maggots that were present in rotting flesh) arose spontaneously from non-living things.Pasteur was able to disprove this theory and he established the germ theory of disease. This theory states that germs/microbes cause disease and all living microorganisms come from pre-existing living things. Koch determined that each disease is caused by a specific microorganism. Pasteur contributed in finding that microorganisms were the cause of wine, beer and vinegar spoilage. He discovered that the solution to the wine and vinegar problems was to heat these solutions long enough to kill the contaminating bacteria that were present after fermentation. This was the beginning of the process of pasteurisation that is still widely used today. He found that the rotting of food was due to the activity of living organ isms. He carried out his famous swan necked flask experiments to gain evidence to support his theory germ theory of disease. These experiments involved using flasks that were not sealed. Meat broth was boiled in the flasks and as they cooled the air was drawn in from the outside. Any microorganism present in the air did not reach the broth as they were trapped in the narrow necked and curve of the glass. No fungal or bacterial growth was observed in these flasks. Bacterial growth occurred if the curve of the glass was broken off and the contents of the flask exposed to the air. This added further evidence to disprove the theory of spontaneous generation. It proved that the organisms that contaminated the broth and caused it to decay was carried in the air and not spontaneously generated. After 150 years the broth in the swan necked flask is still free of bacterial growth. Pasteur also uncovered the relationship between microorganisms and disease, and as specific bacteria became known for specific diseases the spontaneous generation became less and less widely supported and the germ theory of disease was more widely accepted. Koch developed the agar plate technique for growing microorganisms that is still used today and used it to culture the isolated anthrax bacillus (AB). He studied the blood of sheep that had died from AB and identified the rod shaped bacteria that he isolated and grew in cultures. These cultured bacteria were injected into healthy sheep that subsequently developed AB.These experiments added further weight to the germ theory of disease as they showed that a microorganism grown outside the body caused a disease. Koch determined that each disease is caused by a specific microorganism.The principals he used to identify the specific microorganism that was responsible for a disease came to be known as Kochs postulates and are still used today to identify the specific microorganism that causes a particular disease.Kochs Postulates:1. The same microorganism must be present in every diseased host.2. The microorganism must be isolated and cultured in the laboratory and accurately described and recorded. 3. When a sample of the pure culture is inoculated into a healthy host, this host must be able to develop the same symptoms as the original host.4. The microorganism must be able to be isolated from the second host and cultured and identified as the same original species. One of Kochs subsequent big breakthroughs was the discovery of the bacterium responsible for tuberculosis, mycobacterium tuberculosis. He was also responsible for identifying the bacteria that causes cholera.

3.2 Distinguish between: Prions Viruses Bacteria Protozoans Fungi Macro-parasitesAnd name one example of a disease caused by each type of pathogen

A prion or proteinaceous infectious particle is a protein that is capable of causing disease. Unlike other types of pathogens, prions do not contain any genetic material (DNA or RNA). They are smaller than smaller than all other pathogens. Normal prion proteins are coded for by genes in an organisms DNA. It is unclear what the function of these prion proteins is, but they are present mainly in the nerve cells of the brain. Normal prion proteins do not cause disease and can be destroyed by heat.A mutation to the gene that codes for these normal proteins causes the production of a different form of this prion protein. This form has a different structure and is the disease-causing prion. This prion is also resistant to most normal methods used to break down proteins and cannot be destroyed by heating or treating with chemicals.Infectious prions are capable of multiplying and are thought to do this when they come into contact with the normal prion proteins, altering their structure and changing them into infectious prion proteins.Prion diseases cause degeneration of brain tissue. Humans may be affected in two ways: acquired infection (eg; through food or medical procedures.) or through apparent hereditary transmission. This means that prion diseases are unusual as they can be both infectious and hereditary diseases.Diseases caused by prions are called spongiform diseases because the brain tissue of individuals that are infected by these diseases is full of holes, like that of a sponge. All of these diseases are fatal.An example such a disease is kuru, a disease that was found in tribes in the Fore highlands of Papua New Guinea. The symptoms include uncontrollable shaking, continuous trembling, and grimacing of the face which led to the name laughing death. It was transmitted by eating, during funeral ceremonies, the infected brain tissue of dead relatives. It was usually fatal within 6-12 months. Only women and children contracted the disease, as the men did not take part in the burial ritual. The transmission of disease stopped when the cannibalism practices of the tribe stopped.Viruses are non-cellular pathogens that have both living and non-living characteristics. They contain genetic material and are able to pass on hereditary information (a characteristic of living organisms), are not composed of cells and can be crystallised (characteristics of non-living things). They are the smallest known reproducing thingsViruses are larger than prions and many times smaller than bacteria. A virus is made up of a protective protein coat that encloses the genetic material, which may be either DNA or RNA. Viruses are unable to reproduce on their own and can replicate only inside host cells. The viral protein coat contains chemicals that allow the virus to attach itself to the surface of the host cell. Once the virus attaches itself to the cell, it enters and takes of the cells reproductive mechanisms to make copies of itself. The cell becomes so full of copies that it dies and bursts, releasing the new viruses so they can repeat the process with other host cells.At present, there are no cures for viral diseases but there are vaccines which reduce their incidence. Viral diseases include measles, mumps, chickenpox, AIDS, Influenza and glandular fever. Bacteria are single-celled procaryotic organisms. Their genetic material is a single large chromosome a circular thread of DNA double helix. They are larger than viruses but smaller than protozoans and vary in size from 0.5 to 100 micrometres. Bacteria are classified on the bases of their shape they can be a spherical shape (coccus), a rod shape (bacillus), a spiral shape (spirillum), a comma shape (vibrio) or an oval shape (rickettsiae). Bacteria reproduce by asexual reproduction using the process of binary fission (dividing in two). The time it takes for the number of bacteria to double is known as the generation time. This varies for different species and is between 10 minutes and 24 hours. This means that many bacteria can be produced in short space of time.Some bacteria are beneficial whereas others are not. Those that arent release toxins or chemicals that are harmful to the hosts body. These toxins can either inhibit protein synthesis, damage cell membranes, disrupt transport of material across cell membranes, or interfere with normal nerve function. Some examples of diseases that are caused by bacteria include tetanus, meningococcal disease and food poisoning.Protozoans are single-celled eucaryotic organisms. They usually reproduce by the process of asexual binary fission and range from 1-300 micrometresSome protozoans possess a long whip-like tail called a flagellum to enable them to move about. These protozoans are known as flagellates. Ciliates have many hair-like projections called cilia surrounding the cell. These beat rapidly to propel them along. Protozoans such as Amoeba possess projections of the cytoplasm, called pseudopods, to move them around. Sporozoa are protozoans such as Plasmodium that do not have structures for motion and reproduce by spores. Diseases caused by protozoans include malaria, giardiasis and trypanosomiasis.Fungi are eucaryotic organisms. Fungi do not contain chlorophyll and are not capable of producing their own food. They can be unicellular, such as yeasts, or multi-cellular, for example mushrooms. Most are composed of a system of microscopic tubular filaments or threads known as hyphae, which branch and spread to form a structure known as mycelium. Fungi range in size (micro to macroscopic), and also in reproductive methods (asexual, sexual or even both). Most fungi are saprophytic (live on dead organisms) and hence act importantly as decomposers. Most pathogenic fungi are dermatophytes (live in skin, nails and hair), and a small number cause diseases such as candidiasis (thrush) and athletes foot (tinea).Micro-parasites are parasites that are visible to the naked eye and are larger than other pathogens. They are multicellular eucaryotic organisms that vary in size from the tiniest louse to very long tapeworms. Some macro-parasites cause disease directly, whereas others will act as vectors in the transmission of a disease. Macro-parasites can be divided into two groups:1. Endoparasites live inside the hosts body and include flatworms (tapeworms) and roundworms. They cause diseases such as taeniasis (tapeworm disease), and elephantiasis (caused by a filarial worm).1. Ectoparasites are parasites that live outside the body, usually sucking blood. Examples include mosquitoes and lice. Some of these parasites inject toxins while feeding; these can cause inflammation, allergic reactions and sometimes partial paralysis. Ectoparasites can also act as vectors for the transmission of other pathogens. The flea is vector for the bacterium Yersinia pestis, which causes bubonic plague.

3b) Gather and process information to trace the historical development of our understanding of the cause and prevention of malaria.Malaria is one of the most prevalent infectious diseases in the world today, with more than 300 million cases reported and 1.5-3 million deaths, mostly of African children under 5 years old, each year. Malaria starts suddenly and is characterised by intermittent violent chills and intense fevers, severe headaches, convulsions and delirium. Anaemia is also a common symptom, as well as an enlarged spleen. Death will result when the tissue dies from a lack of oxygen or serious brain/kidney infections.The historical development of our understanding of the cause of malaria can be broken up into three stages: Recognising the symptoms and hypothesise as to the cause Discovering the microorganism responsible Determining the life cycle and mode of transmission of the protozoan that causes malaria. Step 1: Recognising the symptoms and hypothesising the causeThe symptoms of malaria have been reported since the beginnings of recorded history. In Chinese methodology for example, three demons are pictured: One with a hammer, one with cold water, and one with a stove. These demons were held responsible for the headache, chill and fever suffered with malaria. The Greeks, however realised that those who live in swampy areas had a higher chance of developing the disease. Hence they believed that it may have been due to the drinking of the swamp water, or the inhalation of the dirty air that resulted in the disease. Step 2: Discovering the micro-organism.Pasteurs and Kochs work ignited the search for the cause of malaria. In 1880 Charles Laveran discovered the pathogen that causes malaria while looking at the blood of malaria patients. This organism was a protozoan that he classified as Plasmodium.In 1885, Golgi, an Italian neurophysiologist, established that there were at least two forms of the disease: one that causes a fever third day. In 1886, he observed that each of these forms produced differing amounts of new parasites (merozoites) and that the peak of the fever coincided with the release of the merozoites into blood.Later, other scientists found that there was in fact two more malaria parasites and the initial pathogens name was changed form Plasmodium to P. falciparum. Step 3: Determining life cycle of the parasite and the mode of transmission.In 1897, Ronald Ross, demonstrated that the malaria parasite could be transmitted from infected patients to mosquitoes. He tested this hypothesis in birds and was successful in showing that the mosquitoes were able to pass the malaria parasite from bird to bird. He determined the main steps in the cycle of transmission of the malaria parasite and identified that only a certain strain of mosquito transmitted the malaria parasite.Life Cycle of Malaria:The mosquito ingests infected red blood cells, the cells are digested and the malarial parasite is released in the intestine of the mosquito. The parasites migrate from the intestine to the salivary glands where they remain ready to enter another host when the mosquito next feeds.

Prevention of MalariaAlthough drugs are available for the treatment of malaria, a complete cure is difficult. This is because the parasite can remain dormant for many years in the liver before becoming active again. Different drugs are used against the different stages of the malarial parasite. Malaria is still one of the most serious infections in the world and is particularly common in some tropical and sub-tropical areas. The Anopheles mosquito, the main carrier of malaria is common in these areas.Control of the disease is also becoming more difficult as mosquitoes become increasingly resistant to chemicals such as DDT that have been effective against them in the past. Eradication of the vector for the malarial parasite is proving to be virtually impossible.History of Prevention:The ancient Chinese used the anti-fever properties of the Qinghao plant in order to treat malaria. In order to prevent it, however, the ancient Greeks and Romans decided to build drains to remove stagnant water. After they had done this, the incidence of these fevers fell.In the mid-1600s the first drug to treat malaria was produced. This was known as quinine. It was extracted from the bark of the Peruvian cinchona tree. After it was shown that the mosquito was responsible for the transmission of malaria, procedures were followed to reduce the chance of being bitten by a mosquito. Many areas where the mosquitoes were bred were drained, bodies of water were sprayed with oil to prevent breeding and protective clothing was worn to reduce the risk of being bitten.Following this, a range of drugs were developed, each of which had a positive immediate effect such as Atebrin, but over time, the virus evolved and became resistant, hence reduces the drugs effectiveness. Additionally, the use of DDT was employed to eradicate large numbers of mosquitoes. This also resulted in the same consequence where initially large populations were wiped out, but over time, the species evolved and became resistant to the pesticide.Overall, the best method of prevention is those that reduce the risk of being bitten

3c) Describe an infectious disease in terms of its cause, transmission, host response, major symptoms, treatment, prevention and control.Disease: InfluenzaCause: Influenza is caused by infection with the influenza virus. There are two types (A and B) are the two main types of influenza viruses that infect humans, and each contains RNA surrounded by a protein coat. They differ from each other as they carry different antigens on their surfaces. There are a number of different strains of both the influenza A and B viruses.Transmission: The transmission of influenza virus can be either direct of indirect: Direct contact: The viral particles are inhaled through the nose and mouth in droplets that have been exhaled by an infected person when they sneeze or cough. Indirect contact: The infected person touches the respiratory tract, and then touches some else, such as a handrail. A second person touches the handrail and soon afterwards, then places their hand on their nose or mouth.Host Response to the influenza virus: The immune response is initiated by the presence of the virus in the body. This produces antibodies and other immune-response cells specific for the particular strain of the influenza virus that has infected the body. The immune response is responsible for destroying the viral particles that have invaded the body.Major symptoms of Influenza: Fever, Headache, inflammation of the upper respiratory tract, sore throat, muscle pain, coughing and sneezing as well as nasal catarrh (inflammation the mucous membrane causing excess production of mucous).Treatment: Influenza is caused by a virus and therefore there is no treatment that will cure it. The main method of treatment is to relieve the symptoms, get plenty of bed rest and drink extra fluids. Bed rest allows the body to fight the disease and then recover. Aspirin or paracetamol can be given to help alleviate headaches, sore throat and muscle pain and to reduce fever. Antibiotics are ineffective in the treatment of viral diseases, but can be used if secondary bacterial infections develop.Prevention: The primary method of prevention of influenza involves the use of influenza vaccines. New vaccines are produced each year and are derived from the influenza A and B viruses that circulated during the previous influenza season. If the virus vaccine and the circulating virus are closely related, the effectiveness is fairly high. As the influenza virus is constantly changing by mutation, the vaccines have to be constantly updated. Other strategies include wearing protective masks, avoiding crowded areas and ensuring that adequate nutrition and sleep is obtained.Control: To reduce the spread of the disease through the population a number of strategies could be employed. These include: Implementing immunisation programs along with education programs to encourage at risk individuals to be vaccinated. Isolation infection individuals to reduce the spread of influenza throughout the population this would include infected individuals remaining at home to stop the spread of the virus to their work or school colleagues.

3a) Perform an investigation to model Pasteurs experiment to identify the role of microbes in decayAim: To model Pasteurs experiment to identify the role of microbes in decayHypothesis: The flask that has the S-shaped glass will not show signs of microbial growth. The flask with the straight glass tubing that is open to the air will show signs of microbial growth.Equipment: Beef broth made from beef stock cubes, filtered to remove any cloudiness 2 conical flasks: each with a single-hole stopper to fit. Glass tubing bent into an S-shape fitted into one of the stoppers Straight glass tubing fitted into the other stopper Heating equipment (Bunsen burner, tripod, gauze mat etc.)Risk Assessment: While handling glass flasks and stoppers, take caution as glass is fragile and breakage may cause injury. Wear safety glasses while boiling the broth as hot water may spit out the glass tubing. Be cautious with the Bunsen burner, flames and hot equipment can cause severe burns.Method:0. Add the filtered beef broth to each of the flasks until they are approximately one third full.0. Fit the stoppers to the flasks0. Heat each flask so that it boils for 20 minutes. After boiling, ensure there is a small amount of water trapped in the S-bend 0. Leave flasks out of direct sunlight for several weeks.0. Every 2-3 days, observe the contents of the flask

Results: After several weeks we observed that the flask with the S-bend has had no microbial growth while the flask with the straight glass tubing open to the air has substantial microbial growth in the flask.Conclusion: we were successful in modelling Pasteurs swan-necked flask experiment and found that his hypothesis that microbes in the air caused the decay of foods was correct.

3.3 Identify the role of antibiotics in the management of infectious disease Antibiotics are chemicals made by microbes that can kill or stop the growth of bacteria and fungi without destroying the host. In 1928 Alexander Fleming discovered the first antibiotic, penicillin. It was not able to be used at this stage and was not until a decade later that Howard Florey (an Australian) ad Ernst Chain purified penicillin. It then became available for medical use in 1941.Penicillin is a naturally occurring substance produced by a living thing and since its discovery many synthetic forms of antibiotics have been made. (Eg. Tetracyclines, cephalosporins, sulphonamides)Broad-spectrum antibiotics, such as sulphonamides, act on a wide range of bacteria and are useful when the identity of the bacteria causing infection is not known. Other types of antibiotics, such as penicillin, act on only one or two types of bacteria and are known as narrow-spectrum antibiotics.The antibiotics act on the bacteria to destroy them in a number of different ways: Some accumulate in the cells of the bacteria and prevent them from forming a new cell wall when they are dividing. (Eg. Penicillin.) Some destroy the cell membrane, effectively destroying the bacteria. (Eg. Amphotericin) Some interfere with protein synthesis so the bacteria are unable to make essential compounds, resulting in the death of the cell. (Eg. Erythromycin.)

3d) Discuss problems relating to antibiotic resistance Bacteria, during the normal process of natural selection, have evolved strains that are resistant to many, if not all, of the antibiotics that are used to treat infectious diseases in the world today. Antibiotic resistance is being further accelerated by a number of common practices. These include: The overuse of antibiotics for the treatment of many diseases and not just bacterial diseases. Eg: prescribing of antibiotics for the treatment of coughs, colds and the flu. These are caused by viruses which are not affected by antibiotics. This practice just gives the bacteria more chances to build up populations of resistant strains. A very common practice is only taking the course of antibiotics until the symptoms of the particular disease disappear. This is dangerous as not all the bacteria may be killed before the end of the course of tablets. This allows the bacteria that are resistant yet another chance to survive, reproduce and develop more populations of resistant strains.Microorganisms that cause diseases once easily cured, such as tuberculosis, have developed resistant strains that are not responding to the cheaper first-line antibiotics. As a result of this, the effects of these diseases are now more severe and because they take much longer to cure, the infectious period is longer, meaning that there is a greater chance of passing on the resistant strain of the microorganism to other members of the community. When second-line or third-line antibiotics have to be used they are usually much more expensive and more toxic. The drugs needed to treat multi-resistant tuberculosis are 100 times more expensive than those used to treat the non-resistant forms, and in countries where this is too expensive to use, the disease is untreatable and therefore spreads. Antibiotic resistance is a major problem for the treatment of some diseases, as the current trend indicates that in the near future some diseases will have no treatment, unless there is a significant breakthrough in producing more effective drugs.Strategies to slow the development of antibiotic resistance: Only prescribe antibiotics for bacterial infections and when it will be of benefit to the patient The antibiotic prescribed should target the pathogen and not be broad-spectrum Not take antibiotics for viral infections such as the cold and flu Taking the whole course of the antibiotic and not stop when the symptoms go away Never take antibiotics that are prescribed for someone else

4.1 Identify defence barriers to prevent entry of pathogens in humans: Skin Mucous Membranes Cilia Chemical Barriers Other Body secretionsThe first line of defence is a non-specific defence and involves the body using both chemical and physical barriers to try to prevent the entry of pathogens into the blood and tissues. The most vulnerable area of the body for the entry of the body for the entry of pathogens are the openings, such as the mouth and nose, and the internal passages, such as the alimentary canal and urinogenital tract. The skin is a physical barrier that forms a tough outer barrier that covers the entire body and prevents penetration by microbes. It is fairly dry which helps to prevent the growth of pathogens. The skin also contains its own population of harmless bacteria that help to stop the invading microbes from multiplying. Oil and sweat glands in the skin produce antibacterial and antifungal substances that further inhibit the growth of invading pathogens. If the continuous barrier is cut, the blood clots almost immediately to produce a temporary patch to maintain the barrier until new skim forms. The respiratory, digestive, reproductive and urinary tracts are covered with membranes that produce a thick layer of mucus which traps entering pathogens. The pathogens are held in the mucus until they are removed by processes such as coughing and sneezing. The mucus can contain an antibody that prevents bacteria and viruses from attaching to the surface. The mucus also provides a moist, nutritious layer in which the harmless microbes live and produce substances that inhibit the growth and entry of pathogens.Cilia are tiny hairs that line the respiratory surfaces of the trachea and bronchial tubes. The cilia are constantly beating in an upwards direct to move the mucus containing the trapped pathogens towards the throat where they are then removed by coughing or sneezing or swallowing.Different types of chemicals secreted in different parts pf the body act as a barrier to the invading pathogens. In the alimentary canal, pathogens entering with food or drink, or swallowed with mucus, will be destroyed by the acidic conditions of the stomach or the alkaline conditions of the intestines. The urinary and vaginal openings and the surface of the skin are also acidic, which inhibits the growth of pathogens. Other body secretions include: Urine is sterile and slightly acidic and flushes and cleans the ureters, bladder and urethra. It also helps to prevent the growth of microorganisms Tears contain lysozymes that destroy the cell walls of some bacteria. As the tears are produced and the eyelid blinks, the surface of the eye is cleaned and the pathogens are washed away. Saliva also contains lysozymes and washes microorganisms from the teeth and the lining of the mouth.

4a) Gather, process and present information from secondary sources to show how a named disease results from an imbalance of microflora in humansThrush is a disease caused by the excessive growth of a yeast-like fungus call Candida albicans. The fungus occurs naturally in the bowel and the vagina, along with a variety of other microflora, and normally causes no problems in a healthy person. If, however, the environment changes, the balance of these microorganisms may be disturbed and an overgrowth of Candida may occur, especially in the vagina.Symptoms of thrush include vaginal itching and discomfort, thick discharge, redness and swelling, stinging or burning experience may be experience when passing urine. It must be noted, however, that other conditions, such as genital herpes or urinary tract infections, may display the same symptoms and an accurate initial diagnosis is important.A change in the environment of the vagina leading to thrush may be caused by the oral contraceptive pill, diabetes, pregnancy, immune system disorders and general illness. The use of some antibiotics can also be a major cause of this disease because these drugs kill most, if not all, types of bacteria in the body. The resulting imbalance of microflora leads to the excessive growth of Candida, and thrush-like symptoms begin to appear. In addition, a change in pH of the vagina caused by spermicides and feminine hygiene products can also lead to the overgrowth of Candida.Treatment usually involves the use of antifungal cream, but also may involve the insertion of suppositories such as micronazole. In some cases, the insertion of natural yoghurt into the affected area may help to retain the balance of microflora in this region.Prevention techniques involve careful washing of vulnerable areas, the avoidance of some types of antibiotics and the practice of wiping front to back after using the toilet to avoid spreading yeast from the anus to the vagina.

4.2 Identify antigens as molecules that trigger the immune response An antigen is any molecule the body recognises as foreign and that triggers the immune response.On the surface of cells in the body, there are marker molecules that allow the body to recognise the cells as self.When pathogens enter the body, they have chemical markers, called antigens, on their surface; the immune system recognises these as not belonging to the body (non-self). The presence of these antigens causes the immune response to be activated to destroy the foreign organisms. It is not only pathogens that have antigens on their surface. Any cell, cell fragment, protein debris or toxin produced by bacteria can also contain antigens. The venom of poisonous snakes contains a number of antigens. In these cases the immune response will be activated because the body recognises all these antigens as foreign molecules.

4.3 Identify defence adaptations, including: Inflammation response Phagocytosis Lymph system Cell death to seal of pathogenThe inflammation response is a non-specific defence mechanism and occurs at the site of infection. When the cells are infected or injured in some way, the release chemical alarm signals such as histamines and prostaglandins. These chemicals cause the blood vessels to dilate, increasing blood flow to the site of infection or injury and causing the area to become red, hot and swollen. These chemicals also increase the permeability of the blood vessels; this allows the movement of phagocytes from the blood into the tissues so they can attack the invading pathogens. Phagocytes are a special type of white blood cell. Plasma also moves into the tissues, bringing more phagocytes and producing swelling in the area, forcing tissue fluid into the lymph and taking debris and pathogens with it. Chemicals that increase the temperature are released. This inhibits the growth of pathogens, inactivates some enzymes and toxins made by pathogens and increases the rate at which the biochemical reactions occur in the body.Phagocytosis is a non-specific process where white blood cells, called phagocytes, attack foreign substances and engulf and destroy them. Phagocytosis is not always effective as some pathogens can repel phagocytes; some bacteria have special capsules which the phagocytes cannot grasp, and some pathogens escaped before being completely destroyed. Pus is a mixture of dead phagocytes, bacteria, tissue fluid and damaged body cells.Macrophages are the largest phagocytic cells are involved in wound healing, inflammation and the immune response. Macrophages pseudopodia and engulf dead and damaged cells, debris, antibody coated microbes and damaged fatty particles. They then release digestive enzymes and lytic enzymes to destroy the particles. After a macrophage has destroyed the pathogen, parts of the partially digested antigen are displayed on the surface of the macrophage. Contact with T-cells stimulates the production of more helper T-cells for that particular antigen. Thus, macrophages are part of the non-specific response but also involved in the production of specific defence cells.The lymph system is a system of vessels and lymph nodes that returns fluids and proteins to the blood. The lymphatic system is important in controlling tissue fluid balance, lipid transport and defence against disease. Lymph is a colourless fluid that drains from the interstitial spaces into lymph capillaries, blind end tubes with valves which prevent lymph flowing back into the tissues. The lymph passes through the lymph nodes and eventually joins up with the circulatory system at the heart. Lymph nodes are located along the lymphatic vessels and act as filters, removing microbes, foreign particles, tissue debris and dead cells from circulation. Cell death to seal off pathogen: a cluster of cells may surround the pathogen and damaged tissue. A cyst may even form. The area is sealed off and other cells such as white blood cells and healthy cells may be sacrificed to make sure the pathogen is sealed off.

4.4 Explain why organ transplants should trigger an immune response When a person has an organ transplant, the new organ they are receiving from somebody else has different antigens. The transplanted organ is therefore identified as foreign and the immune response is activated to attack the organ in order to defend the body. To try to prevent this from happening, the tissue type of the donor is matched to the recipient as closely as possible so that there is a high number of matching marker molecules. This will mean that there are fewer foreign (antigen molecules) on the surface, a situation which may lead to less violent immune response.The patient can also be treated with immunosuppressant drugs, which will also lessen the immune response so that the transplanted organ is not attacked. This has the disadvantage of making the patient more susceptible to infection from pathogens and they must take precautions (such as isolation) to reduce their potential exposure to any infections.

5.1 Identify the components of the immune response: Antibodies T Cells B CellsT cells are lymphocytes that are produced in bone marrow and mature in the thymus gland where they are programmed for a specific antigen. T cells provide cell-mediated immunity, being partly effective against body cells which have been infected by a virus or other pathogen. There are many different types of T cells; killer T cells (cytotoxic T cells), helper T cells and Suppressor T cells. Memory T cells recognise the antigen if it is reintroduced. Cytotoxic cells destroy cells identified as non-self. They are formed when either a macrophage or an infected cell displays the antigen. The T cell binds with the infected cell and inserts a toxic chemical called perforin, a protein which causes the cell membrane to rupture, and the cell lyses (disintegrates). They also target cancer cells and foreign graft cells. Helper T cells stimulate the production of plasma cells and help activate B cells to produce antibodies. Many B cells cannot go into production unless helper T cells for that antigen have first acted. Helper T cells secrete chemicals, such as lymphokines and interleukins, which cause activated B cells or T cells to divide and also to stimulate the macrophages for phagocytosis. The production of Killer T cells is stimulated by helper T cells. Suppressor T cells turn off the immune response and suppress the production of antibodies. Some believe they are actually a form of helper T cells. B cells are white blood cells, formed in the bone marrow like all white blood cells. They mature in the bone marrow and are released into the blood stream. They provide what is called antibody-mediated immunity. The presence of an antigen activates B cells to divide and differentiate into either plasma cells or memory cells. Plasma cells secrete immunoglobulins called antibodies with a shape compatible to that of the antigen. The antibody can bind with its particular antigen to form an antibody-antigen complex. This binding destroys the antigen by either immobilising it, or by blocking and neutralising an active binding site of the antigen, or by causing the antibody-antigen complexes to agglutinate (stick together) and clump which makes them easier to eliminate by phagocytosis. The memory B cells remain in the body for a long time and can identify that particular antigen. A later infection of the same antigen will be detected by the memory cells, which cause a rapid, large-scale production of the needed antibody. Memory cells provide immunity. Antibodies are proteins called immunoglobulins. They are produced in response to the presence of an antigen in the body. When the appropriate B cells are activated they form plasma cells that produce antibodies, the antigen binding sites of which match the shape of the antigen they are specific for, much like enzymes being substrate specific. These antibodies then seek out the antigen and bind to a part of it, forming the antigen-antibody complex, which causes the deactivation of the antigen.

5.2 Describe and explain the immune response in the human body in terms of: interaction between B and T lymphocytes the mechanisms that allow interaction between B and T lymphocytes the range of T lymphocyte types and the difference in their roles

5.3 Outline reasons for the suppression of the immune response in organ transplant patientsWhenever a patient receives an organ transplant, the bodys immune system recognises the foreign tissue as an antigen and the immune response is triggered. This often happens despite the fact that the tissue proteins of the donor are matched as closely as possible with those of the recipient. Killer T cells, macrophages and antibodies begin to attack the tissue that has been distinguished as non-self by the lymphocytes and tissue rejection usually follows. As a result, special immunosuppressive drugs need to be administered to organ transplant recipients to prevent this rejection process.

Outline the way in which vaccinations prevent infectionImmunisation is a process which stimulates the immune system to produce lymphocytes or antibodies to fight an infection, giving immunity to that disease. Vaccination is a method of providing immunisation, in which weakened or dead pathogens are introduced to the body.Vaccines act as an antigen, inducing the immune response; plasma cells and memory cells are produced. The vaccine does not cause the disease or the symptoms so the plasma cells are not really needed. The memory cells are important as they give the body immunological memory for a particular pathogen. If that pathogen enters the body, the circulating memory cells can respond very quickly and in greater numbers so that the person does not suffer the symptoms or the disease. As the number of memory cells can decrease over time, booster injections are sometimes needed to maintain immunity. Vaccines can contain either the killed bacteria or viruses (e.g. cholera or typhoid); living attenuated forms of the pathogen (e.g. rubella or poliomyelitis0; or a toxoid (e.g. Tetanus or diphtheria).

5a) Evaluate the effectiveness of vaccination programs in preventing the spread and occurrence of once common diseases including smallpox, diphtheria and polioMany diseases including smallpox, diphtheria and polio were once very common and caused widespread suffering and many deaths. Vaccination programs have been one of the most successful programs used in preventing the spread and occurrence of these diseases. Since the introduction of vaccination programs such as the Expanded Program on Immunisation (EPI), launched by World Health Organisation (WHO) in 1974, the percentage of the worlds infants immunised against 6 target diseases has increased from 5% in 1974 to 80% in 1997. This has prevented approximately three million deaths per year. Mass immunisation programs have not only been effective in reducing the occurrence of disease in the individual but also decreased the spread of disease through the population.Vaccination programs have been very effective in preventing the spread and occurrence of the disease smallpox. The program has been so successful that it has totally eradicated the disease from the world. Smallpox has killed more people than any other infectious disease and was responsible for one-tenth of all deaths in Europe in the 19th century.A vaccine for smallpox was developed by Edward Jenner in 1798 but was not widely used. In 1967 there were still 33 countries where smallpox was still a major health problem. The WHO carried out worldwide immunisation programs that involved routine mass immunisations with supplementary doses given on special immunisation days. People who missed out on the routine immunisations were targeted and special surveillance teams were sent out to all possible cases of smallpox. In 1979 WHO declared they had eliminated the virus from the world population and eradicated the disease smallpox. Diphtheria is a deadly disease, often killing its sufferers within a week. Mortality rates were very high with two thirds of the deaths being children under the age of five. In 1921, there were 206,000 cases with 15,000 deaths in the US. Immunisation programms introduced in Australia, Europe and other developed countries in the 1930s and 40s resulted in a rapid decrease in the incidence of diphtheria. However, in 1980 there were still nearly 100,000 cases worldwide. When the WHO introduced the EPI in 1974 only 5% of children in the world were immunised against diphtheria. Infants were given 3 doses of the combined diphtheria-tetanus-pertussis vaccine. By 1990 the number of children immunised increased to 80% and resulted in a greatly decreased mortality rate worldwide. By 2005 the incidence of diphtheria had dropped to just over 8000 cases, 6000 of these were in the South-East Asia region. This vaccination program was very effective as the global incidence dropped significantly. Polio is an extremely serious disease with death occurring in 50% of cases and nerve damage and paralysis in 50% of sufferers. After a safe vaccine was developed by Albert Sabin, and following widespread immunisation there was a 60-70% reduction in the incidence of the disease. Polio had become very rare in industrialised nations and the incidence decreased even further after the EPI was introduced in 1974.A global Polio eradication Initiative was launched in 1988 by the World Health Assembly (WHA). When this program began there was 350,000 cases in 125 countries with more than 1000 children being paralysed each day. In 1997, almost 450 million children under five were immunised during National Immunisation Days. By 2000 there was only 719 cases of polio, thats a 99% reduction of cases. At the end of 2006 on four countries experienced fewer than 7000 cases reported. The types of vaccination programs and the planted implementation of these vaccination programs have been very successful in reducing the spread and occurrence of the once common diseases smallpox, diphtheria and polio. Smallpox has been completely eradicated and the occurrence and spread of diphtheria and polio has been drastically reduced due to the successful implementation of planned vaccination programs.