Infection & Response

• What is a pathogen? A microorganism that causes an infectious disease
• How do pathogens spread? [3] - Direct contact - Water or air - Vectors
• What are the 4 types of pathogens? - Bacteria - Viruses - Protists - Fungi
• How can you reduce the spread of an infectious disease? [4] - Simple hygiene measures - Destroying vectors - Isolating infected individuals - Vaccination
• What are viruses? Viruses reproduce rapidly within a body's cell, causing damage to the cells.
• What is measles? Measles is a disease caused by a virus.
• What are the symptoms of measles? Fever and a red skin rash
• What is HIV and what does it cause afterwards? Human Immunodeficiency Virus, and causes AIDS afterwards.
• How does HIV spread? - Sexual Contact - Exchange of bodily fluids
• What does HIV do? At first, HIV causes a flu-like illness. If untreated, the virus enters the lymph nodes and attacks the body's immune cells. However, taking antiviral drugs can delay this happening. Late stage HIV, or AIDS, is when the body's immune system is damaged and cannot fight off any other diseases.
• What is TMV? Tobacco Mosaic Virus
• What pattern does TMV leave? It leaves a mosaic pattern of discolouration that reduces the chlorophyll content of leaves.
• What does TMV affect? Photosynthesis and plant growth.
• How does Bacteria damage cells? Damaging it directly or producing toxins.
• What is salmonella? A type of food poisoning caused by bacteria.
• What happens when the salmonella bacteria is ingested? The bacteria secretes toxins, which causes fever, abdominal cramps, vomiting and diarrhoea.
• How are chickens protected against salmonella? Chickens are vaccinated against salmonella to control the spread of the disease.
• What is gonorrhoea? It is a sexually transmitted disease caused by a bacteria.
• What are the symptoms of Gonorrhoea? [2] - Thick, yellow or green discharge from the penis or vagina - Pain during urination.
• How can you treat Gonorrhoea? Originally you can treat it with pencillin, but many resistant strains have now appeared. However you can use a barrier method of contraception, e.g. a condom.
• What are protists? Single-celled organisms. (unlike bacteria they are eukaryotic)
• How is Malaria caused? It is caused by a protist. The protist will use a particular type of mosquito as a vector. It is passed on to a person when they are bitten by the mosquito.
• What are the symptoms of Malaria? Severe fever, which reoccurs and can be fatal.
• What is one of the main ways to stop the spread of Malaria? Killing mosquitoes or using mosquito nets.
• What is rose black spot? It is a fungal disease.
• How is rose black spot spread? It is spread when spores are carried from plant to plant by water or wind.
• What are the symptoms of rose black spot? Purple or black spots develop on leaves, which often turn yellow and drop early. The loss of leaves will stunt the growth of the plant because photosynthesis is reduced.
• How can rose black spot be treated? Using fungicides and removing and destroyed the affected leaves.
• What are the body defences against pathogens? - Enzymes - Nose - Skin - Glands - Mucus
• What happens if a pathogen enters the body? The immune system tries to destroy it.
• What three ways can white blood cells destroy pathogens? - Phagocytosis - Antibodies - Anti-toxins
• What is phagocytosis? It is when a White Blood Cell engulfs and digests a pathogen.
• What are antibodies? Antibodies are special protein molecules that attach to antigen molecules on the pathogen. This causes the microorganisms to clump together, so that other white blood cells can digest them.
• What are antitoxins? They are chemicals that neutralise the poisonous effects of toxins.
• What happens when the same pathogen re-enters the body? The white blood cells respond more quickly to produce the correct antibodies. This quick response prevents the person from getting ill and is called immunity.
• What is a vaccination? It is when small quantities of dead or inactive forms of a pathogen is injected into the body. The vaccine stimulates the white blood cells to produce antibodies and to develop immunity.
• What happens if a large proportion of the population has been made immune to a pathogen? The pathogen cannot spread very easily.
• What are antibiotics? They are medicines that kill bacteria inside the body. However they cannot destroy viruses.
• How can you reduce the rate at which resistant bacteria develop? [2] - Doctors should not prescribe them for non-serious infections - Patients must complete the whole course of the antibiotics so that all the bacteria is killed
• Why is it difficult to create an antiviral drug? It would kill the cells in the process as viruses reproduce within a cell.