Communicable Diseases (AQA GCSE Combined Science: Trilogy: Biology): Flashcards

It initially causes a flu-like illness, then attacks the body's immune cells.

Late-stage HIV infection (AIDS) occurs when the immune system is so damaged it can no longer fight other infections or cancers.

HIV can be controlled with antiretroviral drugs, which stop the virus attacking the immune cells.

A widespread plant pathogen affecting many species, including tomatoes.

It gives a distinctive 'mosaic' pattern of discolouration on the leaves.

The discoloured (mosaic) areas of leaf cannot photosynthesise well.

Less photosynthesis means less glucose for growth, so the plant's growth is reduced.

They can reproduce rapidly inside the body and produce toxins (poisons) that damage cells and tissues.

By bacteria ingested in food, or on food prepared in unhygienic conditions.

Fever, abdominal cramps, vomiting and diarrhoea.

These are caused by the bacteria and the toxins they secrete.

In the UK, poultry are vaccinated against salmonella to control its spread.

A sexually transmitted disease (STD) caused by a bacterium.

Symptoms: a thick yellow or green discharge from the vagina or penis, and pain on urinating.

Treatment with antibiotics (although many resistant strains now exist).

Using a barrier method of contraception, such as a condom.

Some are single-celled (e.g. yeast); others have a body made of thread-like structures called hyphae.

Fungi can produce spores, which spread the infection to other organisms.

Purple or black spots develop on the leaves.

The leaves often turn yellow and drop early.

Because leaves are damaged and drop early, the plant carries out less photosynthesis.

Less glucose is made, so the plant's growth is reduced.

Rose black spot is spread in the environment by water or wind.

Using fungicides.

And/or removing and destroying the affected leaves.

An organism that carries a pathogen from one host to another without getting the disease itself.

Protist pathogens often need a vector to spread (e.g. the mosquito for malaria).

A protist (from the Plasmodium group).

The malarial protist has a life cycle that includes the mosquito as a vector.

Recurrent episodes of fever.

Malaria can be fatal.

Preventing the vectors (mosquitoes) from breeding (e.g. removing standing water).

Using mosquito nets to avoid being bitten.

Skin

Nose

Trachea and bronchi

Stomach

Skin: a barrier, and produces antimicrobial secretions.

Nose: hairs and mucus trap pathogens.

Trachea and bronchi: mucus traps pathogens and cilia waft it away.

Stomach: produces acid that kills pathogens.

Phagocytosis

Antibody production

Antitoxin production

The process in which a white blood cell engulfs and digests a pathogen to destroy it.

A molecule found on the surface of a cell or pathogen that the immune system recognises.

A protein produced by white blood cells (lymphocytes) that is specific (complementary) to the antigens on a pathogen, clumping them together for destruction.

A protein produced by white blood cells that neutralises the toxins produced by bacteria.

Small quantities of dead or inactive forms of a pathogen are introduced into the body.

This stimulates the white blood cells to produce antibodies.

The white blood cells respond quickly to produce the correct antibodies.

The pathogen is destroyed before it can multiply and cause illness.

Vaccination involves introducing small quantities of dead or inactive forms of a pathogen into the body.

If most people are immune, there are fewer people who can catch and pass on the pathogen.

This makes it unlikely that an unvaccinated person will become infected (herd immunity).

When a large proportion of the population is vaccinated, the spread of a pathogen is reduced, protecting even those who are not immune.

A medicine (e.g. penicillin) that helps to cure bacterial disease by killing infective bacteria inside the body.

Specific bacteria should be treated with specific antibiotics.

Viruses reproduce inside the body's cells.

It is difficult to develop drugs that kill the virus without also damaging the body's tissues.

They treat the symptoms of a disease (e.g. reduce pain).

They do not kill pathogens.

A random mutation in the bacterial DNA gives resistance to the antibiotic.

Resistant bacteria survive the antibiotic and reproduce, so the resistant population increases.

A strain of the bacterium Staphylococcus aureus that has become resistant to antibiotics, making it difficult to treat.

Doctors should not over-prescribe antibiotics, and should not use them for non-serious or viral infections.

Patients should complete the full course of antibiotics.

Reduce the use of antibiotics in agriculture.

From plants and microorganisms.

Digitalis (a heart drug) — from foxgloves.

Aspirin (a painkiller) — from willow.

Penicillin — from the Penicillium mould (discovered by Alexander Fleming).

Penicillin was discovered by Alexander Fleming from the Penicillium mould.

Toxicity — does it have harmful side effects?

Efficacy — does it work?

Dose — what is the optimum amount to give?

Results are peer-reviewed before being published.

Testing done in a laboratory using cells, tissues and live animals.

Trials use healthy volunteers and patients.

Very low doses are given at first; if the drug is safe, further trials find the optimum dose.

A placebo is a 'dummy' treatment containing no drug.

In a double-blind trial, some patients are given a placebo, and neither the doctor nor the patient knows who has the real drug.

They are synthesised by chemists in the pharmaceutical industry.

However, the starting point may still be a chemical extracted from a plant.