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KS3 Biology 8C Microbes and Disease 1 of 20 31 © Boardworks Ltd 2005 2004 Contents 8C Microbes and Disease What are microbes? Uses of microbes How microbes cause disease Fighting disease Summary activities 1 of 31 20 2 © Boardworks Ltd 2005 2004 What are microbes? Microbes are very small living things and are sometimes called micro-organisms. Microbes are so tiny that they cannot be seen with the naked eye. They can only be seen using a microscope. How many different microbes can you name? 1 of 31 20 3 © Boardworks Ltd 2005 2004 Different types of microbes There are three types of microbes: microbes bacteria 1 of 31 20 4 viruses fungi © Boardworks Ltd 2005 2004 Bacteria fact file Bacteria e.g. Salmonella and Streptococcus size: 1/1000 mm shape: Bacteria can be spherical, rod-shaped or comma-shaped. structure: Bacteria are singlecelled organisms, which do not completely have a nucleus. Some cause disease, but many are useful. reproduction: Bacteria reproduce very quickly. Two can very quickly become four, then eight and so on. 1 of 31 20 5 © Boardworks Ltd 2005 2004 Bacterium structure 1 of 31 20 6 © Boardworks Ltd 2005 2004 Viruses fact file Viruses e.g. flu virus and HIV (the AIDS virus) size: 1/1,000,000 mm shape: Viruses have regular and geometric shapes. structure: A virus is a simple organism which does not display ALL the characteristics of living things. They are made up of a protein coating and some genetic material. reproduction: Viruses can only grow and reproduce within other living things. 1 of 31 20 7 © Boardworks Ltd 2005 2004 Virus structure 1 of 31 20 8 © Boardworks Ltd 2005 2004 Fungi fact file Fungi e.g. Penicillium and yeast size: Some fungi can actually be seen with the naked eye, others are slightly bigger than bacterial cells. shape: Fungi come in many different shapes. structure: Fungi have the most complex structures of all the microbes. They feed off other living things. 1 of 31 20 9 © Boardworks Ltd 2005 2004 Fungi (yeast) structure 1 ofof20 10 31 © Boardworks Ltd 2005 2004 Contents 8C Microbes and Disease What are microbes? Uses of microbes How microbes cause disease Fighting disease Summary activities 1 ofof20 11 31 © Boardworks Ltd 2005 2004 Using microbes – bacteria and fungi Microbes have many uses that are based on the fact that microbes can be grown. Bacteria grow in milk to make it ‘go off’. l This type of bacterial growth is used to make milk into yoghurt. l Cheese is another product that is made from milk. Fungi can also be used to make food. The meat substitute Quorn is a protein produced using fungi. 1 ofof20 12 31 © Boardworks Ltd 2005 2004 Using microbes – yeast Yeast is a type of fungus and carries out respiration. The respiration of this microbe can be used in different ways in baking bread and in brewing. The aerobic respiration of yeast is used to make bread rise. Yeast uses the sugar in bread dough to carry out aerobic respiration: glucose oxygen carbon dioxide water energy What gas produced by the aerobic respiration of yeast causes bread to rise? 1 ofof20 13 31 © Boardworks Ltd 2005 2004 Using microbes – yeast The anaerobic respiration of yeast is used to make beer and wine. In this case, the yeast respires without oxygen and produces alcohol (ethanol). This process is known as fermentation. Yeast converts the sugar into alcohol by anaerobic respiration: glucose carbon dioxide ethanol energy How do brewers make sure that yeast respire without oxygen? 1 ofof20 14 31 © Boardworks Ltd 2005 2004 Contents 8C Microbes and Disease What are microbes? Uses of microbes How microbes cause disease Fighting disease Summary activities 1 ofof20 15 31 © Boardworks Ltd 2005 2004 Microbes can cause disease The diseases caused by microbes and their severity depend on the type of microbe. 1 ofof20 16 31 viruses bacteria fungi influenza (flu) food poisoning fungal sinusitis mumps sore throats chickenpox smallpox tuberculosis (TB) tetanus athlete’s foot Onychomycosis polio cholera rabies typhoid German measles viral meningitis whooping cough bacterial meningitis (causes discoloured toe nails) © Boardworks Ltd 2005 2004 Which type of microbe? 1 ofof20 17 31 © Boardworks Ltd 2005 2004 How are microbes spread? The spreading of microbes and disease is known as transmission. 1. Transmission by air A cough or a sneeze can release millions of microbes into the air which can then infect somebody else. 2. Transmission by water Dirty water can transmit many diseases, e.g. cholera, which can be transmitted by drinking. 1 ofof20 18 31 © Boardworks Ltd 2005 2004 How are microbes spread? 3. Transmission by animals An animal can carry a microbe from one place to another, e.g. a mosquito which spreads the malaria parasite. 4. Transmission by contact Many microbes can be exchanged from one person to another by direct or indirect contact: l direct contact by hand; l indirect contact, e.g. by walking on a wet floor already contaminated by someone else who has athlete’s foot; l sexual contact. 1 ofof20 19 31 © Boardworks Ltd 2005 2004 How are microbes spread? 4. Transmission by contact There are other forms of indirect contact, e.g. the transmission of microbes from mother to unborn child. l Transmission through the placenta If the mother develops the HIV/Aids infection, it can be passed on to the unborn child through the placenta. l Transmission via breastfeeding If a child is being breastfed, he or she can also pick up microbes from the mother via the mother’s milk. 1 ofof20 20 31 © Boardworks Ltd 2005 2004 How is the spread of disease stopped? The spread of disease can be prevented by making sure that good hygiene is used in key places such as bathrooms and kitchens. Chemicals called antibiotics can be used to treat bacterial infections. People can be immunized against some diseases by the injection of a vaccine. 1 ofof20 21 31 © Boardworks Ltd 2005 2004 Contents 8C Microbes and Disease What are microbes? Uses of microbes How microbes cause disease Fighting disease Summary activities 1 ofof20 22 31 © Boardworks Ltd 2005 2004 Fighting microbes How does the body fight off microbes that cause disease? 1 ofof20 23 31 © Boardworks Ltd 2005 2004 What do white blood cells do? The human body has a number of natural defences against microbes. Noses are hairy inside to trap microbes! The body also produces white blood cells to help defend it from microbes. Some white blood cells can destroy microbes by engulfing them. white blood cell antigen antibody Some white blood cells are able to produce chemicals called antibodies. These pairing with matching antigens on the surfaces of microbes and so help the white blood cells to engulf microbes. 1 ofof20 24 31 © Boardworks Ltd 2005 2004 White blood cell engulfs microbe – animation 1 ofof20 25 31 © Boardworks Ltd 2005 2004 White blood cell and antibodies – animation 1 ofof20 26 31 © Boardworks Ltd 2005 2004 Contents 8C Microbes and Disease What are microbes? Uses of microbes How microbes cause disease Fighting disease Summary activities 1 ofof20 27 31 © Boardworks Ltd 2005 2004 Glossary l antibiotics – Chemicals prescribed as medicine to kill bacteria inside the body. l antibodies – Chemicals produced by white blood cells to fight microbes that cause disease. l bacteria – The type of microbes that are single-celled organisms. l fungi – The type of microbes that feed off other living things. l immune – Resistance to infection caused by a microbe. l microbe – A very small living thing. l transmission – The spread of a disease from person to person. l viruses – The type of microbes that can only grow and reproduce within other living things. 1 ofof20 28 31 © Boardworks Ltd 2005 2004 Anagrams 1 ofof20 29 31 © Boardworks Ltd 2005 2004 Multiple-choice quiz 1 ofof20 30 31 © Boardworks Ltd 2005 2004