Biology Topic 3 - Infection and Response

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What is a pathogen?
A microorganism that enters the body and causes disease; they cause communicable diseases
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What are bacteria and how do they make you feel ill?
They are very small cells, which can reproduce rapidly inside your body and they make you feel ill by releasing toxins.
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What are viruses and how do they make you feel ill?
Viruses reproduce rapidly inside your body and live inside your cells, which they burst by producing many copies of themselves.
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What are protists?
They are single celled eukaryotes, and some of them are parasites. These live on or inside other organisms and are transferred by a vector (e.g. an insect)
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What are fungi?
They come in many different shapes but most have a body made up of hyphae, which can grow and penetrate human skin/the surface of plants. They can also produce spores, which spread to other plants and animals
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How can pathogens be spread?
Water (drinking/bathing in dirty water), air (breathed in as water droplets), direct contact (touching contaminated surfaces).
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Measles (virus)
-spread by droplets from sneeze/cough -red skin rash showing signs of a fever -can sometimes lead to pneumonia/encephalitis but is usually vaccinated against
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HIV (virus)
-spread by sexual contact/exchanging bodily fluids -initially causes flu like symptoms -attacks the immune cells so it can't cope with other infections (AIDs) -controlled with antiretroviral drugs
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TMV (virus)
-affects many species of plants -causes a mosaic pattern so parts of leaves are discoloured -plant cannot carry out photosynthesis as well so growth is affected
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Rose black spot (fungus)
-causes purple or black spots to develop on the leaves of rose plants -can turn yellow and drop off -photosynthesis can't happen as well -spreads by water/wind -treated by fungicides or ********* the plant of affected leaves and destroying them
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Malaria (protist)
-mosquitoes pick up malarial protist when feeding on infected animal -infects other animals by inserting the protist into the blood -causes repeating fever episodes -reduce spread by stopping mosquitoes breeding -use insecticides and mosquito nets
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Salmonella (bacteria)
-causes food poisoning, fever, stomach cramps, vomiting and diarrhoea -caused by toxins that bacteria produce -eating contaminated food -most poultry is vaccinated against it
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Gonorrhoea (bacteria)
-sexually transmitted disease -pain when urinating and yellow/green discharge from vagina or penis -treated with antibiotics and using barrier methods of contraception
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How can we reduce or prevent the spread of disease?
Be hygienic (e.g. wash hands), destroying vectors, isolating infected individuals and vaccination
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What are the four first lines of defence for the human body?
The skin acts as a barrier and secretes antimicrobial substances, hairs and mucus trap pathogens, the trachea and bronchi secrete mucus to trap pathogens and are lined with cilia, the stomach produces hydrochloric acid to kill bacteria
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How do white blood cells work?
They can engulf and digest foreign cells (phagocytosis). They can produce antibodies specific to the antigens on a pathogen so it can be identified and destroyed by other white blood cells. They produce antitoxins.
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How do vaccinations work?
Dead or inactive pathogens are injected into the body, and the white blood cells produce antibodies to attack them. If the body is reinfected with the same pathogens, the white blood cells will produce antibodies much faster.
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What are the pros of vaccination?
They have helped to control lots of communicable diseases. Big outbreaks of disease (epidemics) can be prevented by herd immunity.
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What are the cons of vaccination?
They don't always work, and you can sometimes have a bad reaction.
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What do painkillers do?
They will relieve pain and reduce the symptoms, but will not tackle the cause of the disease or kill bacteria.
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How do antibiotics work differently and why aren't they used to treat viruses?
They kill or prevent the growth of bacteria, but they can't destroy viruses because they work inside cells.
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What are the stages of antibiotic resistance?
Bacteria mutate and become resistant. When you treat the infection with antibiotics, only the non resistant strains are killed and this allows the resistant bacteria to reproduce with less competition.
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How can the development of antibiotic resistant strains be slowed down?
Doctors should avoid over-prescribing antibiotics, and patients should finish the whole course of antibiotics.
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Name two drugs and the plants they come from.
Aspirin is a painkiller and comes from the chemicals in willow. Digitalis is used to treat heart conditions and comes from the chemicals in foxgloves.
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How did Alexander Fleming discover penicillin?
He noticed that the area around some mould on a. petri dish was free of bacteria. The mould was producing a substance (penicillin) that killed the bacteria.
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Describe the first stage of drug testing.
Drugs are synthesised and tested on human cells and tissues in the lab.
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Describe the second stage of drug testing.
Drugs are then tested on live animals to test for efficacy (whether the drug works), toxicity (how harmful the drug is) and dosage.
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Describe the third stage of drug testing.
The drug is then tested on human volunteers: firstly healthy volunteers to see the side effects, then on patients to find the optimum dosage.
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What are placebos and why are they used?
A placebo is a substance that's like the drug being tested but doesn't do anything, and it is used to see the actual difference the drug makes.
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What is the difference between a blind and a double blind trial?
A blind trial is where the patient doesn't know whether they're getting the drug or the placebo, and a double blind trail is where neither the patient nor the doctor knows (so they aren't subconsciously influenced)
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What is peer review and why is it used?
Peer review is when other scientists check that the work is valid and is done to prevent false claims
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Describe the stages of producing monoclonal antibodies.
A mouse is injected with the chosen antigen, and b-lymphocytes are taken from the mouse. They are then fused with a tumour cell to make a hybridoma, which multiply quickly. They are cloned, and they all produce the same monoclonal antibodies.
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How are monoclonal antibodies used to treat cancer?
Cancer cells have tumour markers on their membranes. Monoclonal antibodies that bind to these tumour markers can be produced and attached to anti cancer drugs (e.g. toxic drug, radioactive substance or chemical). They target + kill the cancer cells.
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How else can monoclonal antibodies be used?
They can bind to hormones and other chemicals to measure their levels. They can test blood samples for certain pathogens. They can locate specific molecules (bind to fluorescent dye)
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What are the problems with monoclonal antibodies?
They cause more side effects than initially expected (e.g. fever,vomiting and low blood pressure), so they are not as widely used.
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Why do plants need nitrates and magnesium ions?
Nitrates are needed to make proteins and therefore for growth (lack of nitrates = stunted growth). Magnesium ions are needed for making chlorophyll (lack of magnesium=chlorosis, yellow leaves)
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What are the common signs of plant disease?
Stunted growth, spots on the leaves, patches of decay, abnormal growth, malformed stems or leaves, discolouration.
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How can diseases be identified?
Look them up in a gardening manual or website, take the infected plant to a lab or use a testing kit to identify the pathogen.
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Give 3 examples of physical defences of plants.
A waxy cuticle, which acts as a barrier. A cell wall made from cellulose and layers of dead cells (e.g. bark on a tree) which also act as barriers.
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Give 2 examples of chemical defences.
Some plants produce antibacterial chemicals (e.g. mint plant and witch hazel). Other plants produce poisons which deter herbivores (e.g. tobacco plants, foxgloves and deadly nightshade)
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Give 3 examples of mechanical defences.
Thorns/hairs to stop animals from touching and eating them. Leaves that droop or curl when something touches them. Cleverly mimic other organisms (e.g. Passion flower has spots to look like butterfly eggs to stop butterflies laying their eggs there)
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Card 4

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Card 5

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