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Infection and response flashcards

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Communicable diseases

What is a pathogen?
A microorganism that causes infectious disease.
Name the four types of pathogen.
Viruses, bacteria, protists and fungi.
Name three ways pathogens can be spread.
By direct contact, by water and by air.
How do bacteria make us feel ill?
They reproduce rapidly in the body and may produce toxins that damage tissues.
How do viruses cause damage?
They live and reproduce inside cells, causing cell damage.
Give two ways the spread of disease can be reduced.
Any two of: hygiene, vaccination, treating infected people, controlling vectors, barrier contraception, destroying infected plant material.
What are the symptoms of measles?
Fever and a red skin rash.
How is the measles virus spread?
By inhalation of droplets from sneezes and coughs.
Why are most young children vaccinated against measles?
It is a serious illness that can be fatal if complications arise.
What does HIV initially cause?
A flu-like illness.
What does HIV attack?
The body's immune cells (unless controlled with antiretroviral drugs).
What is AIDS?
Late stage HIV infection, when the immune system is so badly damaged that it cannot deal with other infections or cancers.
How is HIV spread?
By sexual contact or exchange of body fluids such as blood, for example drug users sharing needles.
What does tobacco mosaic virus (TMV) do to a plant?
Causes a 'mosaic' pattern of discolouration on leaves, reducing photosynthesis and so growth.
How is Salmonella food poisoning spread?
By bacteria ingested in food, or on food prepared in unhygienic conditions.
What are the symptoms of Salmonella food poisoning?
Fever, abdominal cramps, vomiting and diarrhoea, caused by the bacteria and the toxins they secrete.
How is the spread of Salmonella controlled in the UK?
Poultry are vaccinated against Salmonella.
What are the symptoms of gonorrhoea?
A thick yellow or green discharge from the vagina or penis, and pain on urinating.
How is the spread of gonorrhoea controlled?
Treatment with antibiotics, or a barrier method of contraception such as a condom.
Why is gonorrhoea harder to treat than it used to be?
Many resistant strains have appeared; it was once easily treated with penicillin.
What are the symptoms of rose black spot?
Purple or black spots on leaves, which often turn yellow and drop early.
How does rose black spot affect a plant's growth?
Photosynthesis is reduced, so the plant grows less.
How is rose black spot spread, and how is it treated?
Spread by water or wind. Treated with fungicides and/or removing and destroying affected leaves.
What type of pathogen causes malaria?
A protist.
What is the vector for malaria?
The mosquito; the protist's life cycle includes the mosquito.
What are the symptoms of malaria?
Recurrent episodes of fever. It can be fatal.
How is the spread of malaria controlled?
Prevent mosquitos breeding, and use mosquito nets to avoid being bitten.
Name the non-specific defence systems of the human body.
Skin, nose, trachea and bronchi, and stomach.
How does the stomach defend against pathogens?
It produces hydrochloric acid, which kills pathogens.
How do the nose and the trachea and bronchi defend against pathogens?
Hairs and mucus trap pathogens; in the trachea and bronchi, cilia move the mucus away.
Name three ways white blood cells defend against pathogens.
Phagocytosis, antibody production and antitoxin production.
What is phagocytosis?
A white blood cell engulfs a pathogen and digests it.
What do antitoxins do?
They neutralise the toxins produced by pathogens.
What does a vaccine contain?
Small quantities of dead or inactive forms of a pathogen.
How does vaccination prevent illness?
It stimulates white blood cells to make antibodies. On re-infection they quickly make the correct antibodies.
How does vaccinating most of a population reduce the spread of a pathogen?
Most people are immune, so the pathogen cannot spread easily, which protects those not vaccinated.
What do antibiotics such as penicillin do?
Cure bacterial disease by killing infective bacteria inside the body.
Why must specific antibiotics be used?
Specific bacteria need to be treated by specific antibiotics.
Can antibiotics kill viruses?
No. It is also difficult to make drugs that kill viruses without damaging body tissues.
Why is the emergence of antibiotic-resistant strains of concern?
The antibiotics no longer kill them, so deaths from bacterial disease could rise again.
What do painkillers do?
Treat the symptoms of disease. They do not kill pathogens.
Which plant is the source of digitalis?
Foxgloves. It is a heart drug.
Which plant is the source of aspirin?
Willow. It is a painkiller.
Who discovered penicillin, and from what?
Alexander Fleming, from the Penicillium mould.
How are most new drugs made?
Synthesised by chemists in the pharmaceutical industry, though the starting point may be a plant chemical.
What three things are new drugs tested for?
Toxicity, efficacy and dose.
What is preclinical testing?
Testing in a laboratory using cells, tissues and live animals.
Who is used in clinical trials?
Healthy volunteers and patients.
How are doses used in clinical trials?
Very low doses first. If safe, further trials find the optimum dose.
What is a placebo, and what is a double blind trial?
A placebo contains no active drug. In a double blind trial neither patients nor doctors know who gets it.
What happens to the results of drug trials before they are published?
They are scrutinised by peer review: other scientists check the methods and conclusions.

Monoclonal antibodies

What are monoclonal antibodies? Triple onlyHigher tier
Antibodies produced from a single clone of cells, specific to one binding site on one protein antigen.
Which cells are stimulated to make the antibody? Triple onlyHigher tier
Mouse lymphocytes.
What is a hybridoma cell? Triple onlyHigher tier
A lymphocyte combined with a tumour cell. It can both divide and make the antibody.
How is a large amount of one monoclonal antibody obtained? Triple onlyHigher tier
Single hybridoma cells are cloned, then the antibody is collected and purified.
Give three uses of monoclonal antibodies. Triple onlyHigher tier
Diagnosis (pregnancy tests), lab measurement or detection, research with fluorescent dye, treating disease.
How can monoclonal antibodies treat cancer? Triple onlyHigher tier
They carry a radioactive substance, toxic drug or growth-stopping chemical to cancer cells without harming other cells.
What are the disadvantages of monoclonal antibodies? Triple onlyHigher tier
More side effects than expected, and not yet as widely used as hoped.

Plant disease

How can plant disease be detected? Triple onlyHigher tier
Stunted growth, spots, decay, growths, malformed parts, discolouration or pests.
How can a plant disease be identified? Triple onlyHigher tier
Gardening manual or website, laboratory testing, or testing kits containing monoclonal antibodies.
Which plant diseases and pests do you need to know? Triple only
Tobacco mosaic virus (viral), black spot (fungal) and aphids (insects).
What causes stunted growth in plants? Triple only
Nitrate deficiency. Nitrate ions are needed for protein synthesis and therefore growth.
What causes chlorosis in plants? Triple only
Magnesium deficiency. Magnesium ions are needed to make chlorophyll.
Name three physical plant defences. Triple only
Cellulose cell walls, tough waxy cuticle on leaves, layers of dead cells around stems that fall off.
Name two chemical plant defences. Triple only
Antibacterial chemicals and poisons to deter herbivores.
Name three mechanical adaptations of plants. Triple only
Thorns and hairs, leaves that droop or curl when touched, and mimicry to trick animals.