Microorganism Knowledge Organiser - PDF

# Microorganism Knowledge Organiser A microorganism is a living organism, invisible to the naked eye but visible when viewed under a microscope. ## Types of microorganism: ### Bacteria * Single-celled organisms (1 thousandth of a mm long). * Diseases caused by bacteria include: * Food poisoni...

# Microorganism Knowledge Organiser A microorganism is a living organism, invisible to the naked eye but visible when viewed under a microscope. ## Types of microorganism: ### Bacteria * Single-celled organisms (1 thousandth of a mm long). * Diseases caused by bacteria include: * Food poisoning * Cholera * Typhoid * Tetanus ### Viruses * Smaller than bacteria and consist of just a fragment of genetic material inside a protective protein coat. * Some scientists argue that viruses aren't living because they do not follow all of MRS GREN. * Diseases caused by viruses include: * Influenza (flu) * Measles * Chicken pox * AIDS ### Fungi * Vary in size, from single-celled yeast, to massive mushrooms. * Diseases caused by fungi include: * Ringworm * Athlete's Foot * Thrush ## Many microorganisms, rather than causing harm, are actually extremely useful to us. * Examples: * Yeast to make dough, beer and wine * Bacteria to make yoghurt and cheese * Fungi to make antibiotics to treat bacterial infections ## Yoghurt production * Milk is composed of water, proteins and lactose (a sugar). * Bacteria e.g. _Lactobacillus bulgaricus_ break down the lactose sugar in milk to release energy (without oxygen) and produce lactic acid as a result. This process is called **fermentation**. * The result of this is a semi-solid yoghurt with a sour taste. * When lactic acid is produced, the milk becomes more acidic and the proteins in the milk change shape (denature). * This causes the milk to become thick. This process is called **coagulation**. * The drop in pH gradually reduces the reproduction of the bacteria. * The yoghurt is then cooled to 5°c and fruit/ flavours can be added. ## Yeast * A single-celled fungus. * It can respire aerobically (using oxygen) and anaerobically (without oxygen). * During aerobic respiration, $CO_2$ is produced. * In bread-making, the yeast starts off respiring aerobically, producing water and also carbon dioxide to make the dough rise. * The equation for aerobic respiration: Glucose + Oxygen -> Carbon Dioxide + Water + Energy ## How do microorganisms enter the body? * Infected food * Infected water * Inhaled droplets * Vectors e.g. Mosquitos * Blood * Through the placenta * Breastfeeding ## Preventing infectious disease: 1. The skin acts as a major barrier to infection. Bacteria are allowed to live on and feed on the dead skin cells, but can't penetrate it. 2. Tears from the eyes contain lysozyme, an enzyme that breaks down bacteria. 3. The mucous membrane in our breathing tract helps to trap bacteria and other inhaled particles. Sticky mucus catches the bacteria and tiny cilia waft the mucUS up and away from the lungs. 4. Stomach acid kills many of the bacteria found on your food. ## Vaccines are used to prevent infection * A vaccine can be made from weak or inactive versions of the same microorganism that makes us ill. * Once vaccinated, your white blood cells are able to identify and destroy the pathogen. * As a result you don't have any symptoms. * Immunisation programme: when healthcare professionals vaccinate large groups of people against certain diseases. ## Fighting infectious disease: * When a pathogen (disease-causing organism) invades, we increase our body temperature to stop pathogens reproducing. * White blood cells travel in our blood and protect our body from pathogens by attacking them. * If we cut our skin, our blood clots and a scab forms to prevent the entry of pathogens into our body. * Phagocytes engulf pathogens and destroy them. * Lymphocytes make antibodies (chemicals) which stick to the surface of pathogens so that they can no longer invade our cells. ## Antibiotics can be used to treat bacterial infections * Antibiotics are chemicals that kill bacteria or stop them from growing. * They do this by attacking the bacterial cell wall. * The first antibiotic to be discovered was penicillin. * Viruses do not have a cell wall so that cannot be treated with antibiotics. ## Experimental design * **Plan an experiment (6 marks)** * **Remember to use CORMMSS to structure your answer:** * **Change:** What will we change? How? Select 5 different conditions and remember units. * **Organism:** Which organism are we using? You must use the same species throughout the practical. * **Repeats:** You should repeat the entire experiment at least 3 times to improve reliability. You can then take a mean. * **Measure:** What will we measure? How? How long should we wait before measuring? * **Same:** What should we keep the same to ensure that the experiment is fair/valid? You must state at least 2. * **Independent variable:** what we change * **Dependent variable:** what we measure * **Control variables:** what we keep the same to ensure a valid experiment. * **How to draw a graph: 'SLAAP'** * **Scale:** Choose a linear scale that uses up as much of the space given on the page. * **Line:** Connect the data points with a straight line. * **Axes:** Plotted axes correctly. The variable you have changed in your experiment (the independent variable) always goes on the x axis. The variable you have measured (the dependent variable) always goes on the y axis. * **Axes (again):** Include the units. * **Points:** Correctly plot the points on the axes you have drawn. * **Aseptic techniques ensure the microorganisms being investigated do not escape or become contaminated with an unwanted microorganism. E.g. wash hands, disinfect the surface before you begin.** * **Step 1** Sterilise a wire inoculating loop by heating it over a blue flame until it is red hot. * **Step 2** Whilst holding the bacterial broth over a Bunsen flame, carefully remove the lid. The up draught from the flame prevents other bacteria falling into and contaminating the bacterial broth. * **Step 3** Dip the sterile inoculating loop into the bacterial broth to collect a sample of bacteria. * **Step 4** Lift the agar plate lid at an angle of 45 degrees (do not open it fully as other microorganisms may enter) and carefully inoculate the agar jelly with the loop in a zig-zag fashion. Take care not to break the agar surface (as this would encourage anaerobic bacteria to grow). * **Step 5** Seal the lid with 2 pieces of tape. Incubate at 25°C. Any hotter and you may encourage the growth of potentially harmful bacteria. * **Step 6** After a few days your bacteria should have grown. Never re-open the lid. **Key terms:** * **Reliable:** How close repeated measurements are to each other. To check reliability we repeat experiments and look to see how close the results are. * **Validity:** Am I actually measuring what I'm trying to measure? To ensure this we must only change 1 variable at a time and control all others.