pathogens are microorganisms that cause infectiousdisease
pathogens maybe viruses, protists, bacteria or fungi
bacteria and virusesreproducerapidly inside the body
bacteria produces poisons (toxins) that damage tissues and make us feel ill
viruses call illness by living and reproducinginside our cells, using our cell machinery to produce many copies of themselves. This causes our cells to burst, and causes celldamage
protists cause illness by spreading through a vector.Protists are eukaryotes, and illness is spread when the infectedvectorbites or feeds on another organism
fungi cause illness through their body which is made up of hyphae. The hyphae can penetrate human skin causing disease, and produces spores which allows the fungi to spread
spread through water -> drinking or bathing in dirty water
spread through direct contact -> touching a contaminated surface or someone with the disease
spread through air -> breathing in infected cough and sneeze droplets
virus : measles --
affects children
symptoms are a fever and red skin rash, and can be fatal if complications arise
spread through the inhalation of infected droplets from coughs and sneezes
children are vaccinated against measles through the MMR vaccine
virus : HIV --
spread through sexualcontact or sharing of bodilyfluids such as blood which occurs when drug users share needles
HIV initially causes flu-likesymptoms. Unless successfullycontrolled with antiretroviral drugs, the virus attacks the body'simmunesystem.
LatestageHIVinfection (or AIDS) occurs when the body's immune system becomes so badlydamaged it can no longerdeal with other infections or cancers
virus : tobacco mosaic virus --
widespread plant pathogen that affects many species of plants including tomatoes
gives a distinct'mosaic'pattern of discolouration on the leaves
discolouration affects the growth of the plant because it means less absorption of sunlight, less photosynthesis and less glucose and respiration to grow
bacterial diseases : salmonella:
salmonella food poising is spread by bacteria ingested in food, or food prepared in unhygienic conditions
symptoms include fever, abdominal cramps, vomiting and diarrhoea caused by the bacteria and the toxins they secrete
in the UK, all poultry are vaccinated against Salmonella to control the spread
bacterial diseases : gonorrhoea --
sexually transmitted disease, spread by sexual contact
symptoms include thickgreen or yellowdischarge from the penis or vagina, and painurinating.
it is caused by a bacterium, and was easily treated with the antibiotic penicillin until many resistantstrain appeared
the spread can be controlled by treatment with antibiotics or the use of barriermethods of contraception such as condoms
fungal disease : rose black spot --
spread in the environment by wind or water
symptoms are purple and black spots that develop on leaves, which often turn yellow and dropearly. It affects the growth of the plant as photosynthesis is reduced
can be treated using fungicides and removing and destroying the affected leaves
protist disease : malaria --
the pathogens that cause malaria are protists
the malarial protist has a life cycle that includes the mosquito
malaria causes recurrent episodes of fever and can be fatal
the spread of malaria is controlled by preventing the vector (mosquitoes) from breeding so not leaving areas of open still water and using mosquito nets to avoid being bitten
non-specific defences : skin --
acts as a physical barrier
gland secrete antiseptic oils to kill pathogens
good microorganisms (skin flora) compete with bad microorganism for space and nutrients
non-specific defences : the nose --
nose hairs that act as a physical barrier by trapping pathogens
mucus traps pathogens and dust from entering the lungs
non-specific defences : trachea and bronchi --
secrete mucus to trap pathogens
ciliated cells waft mucus upwards to be swallowed, and enter the stomach
non-specific defences : stomach --
produces hydrochloric acid that kills any pathogens swallowed in food or in the mucus
the immune system protects the body against pathogens
if a pathogen enters the body, the immune system tries to destroy the pathogen
white blood cells : phagocytosis --
phagocytes engulf pathogens
this destroys them, preventing them from making you feel ill or reproducing
white blood cells : producing antibodies --
white blood cells produce antibodies that are complimentary to the antigen on pathogens
antibodies bind on to pathogens, meaning the pathogen can no longer reproduce or cause harm
the pathogens start to clump together, and then a phagocyte engulfs them
the antigen and specific antibody is stored in memory cells so if the same pathogen reenters, more antibodies are produced faster leading to an improved immune response
white blood cells : producing antitoxins --
white blood cells produce antitoxins which neutralise the toxins produced by bacteria
vaccination:
smallquantities of a dead or inactive form of the pathogen is injected
the body recognises this pathogen as foreign and stimulates the whitebloodcell to produce antibodies complimentary to the antigen
memory cells store the antigen and the specific complimentary antibody
if the same pathogen reenters the body, the memory cells will recognise it, and the white blood cells will produce more of the correctantibodiesquicker.
this leads to an improved immune response, preventing infection
by immunising a large proportion of the population, the spread of pathogens is reduced as there are less people to catch the disease from (herd immunity)
antibiotics are drugs that kill bacterial pathogens inside the body, without damaging body cells
antibiotics cannot kill viral pathogens because viruses use our body cells to replicate meaning the drug would have to damage our cells to work
antibiotics, such as penicillin, are medicines that help to curebacterialdisease by killinginfectivebacteria inside the body. It is important that specificbacteria should be treated by specificantibiotics.
the use of antibiotics has greatly reduced the deaths from infections bacterial diseases, however the emergence of resistant strains is of great concern
painkillers and other medicines are used to treat the symptoms of disease but do not kill pathogens.
it is difficult to develop drugs that kill viruses without also damaging the body’s tissues.
antibiotic resistance:
a bacterial population, one bacterium will have a DNAmutation, meaning it is resistant to an antibiotic
when the antibiotic is taken, the susceptiblebacteria are killed
this reduces competition for nutrients and space meaning the antibioticresistant bacteria reproduce rapidly, forming a large population that is difficult to control
developing drugs:
drug is tested on tissues in a lab to make sure it isn't toxic, and efficacy
the drug is tested on animals such as mice to check its toxicity and for side effects
drug is given to healthy volunteers at a low dose to check the toxicity, and if there are any unwanted side effects
drug is given to volunteer patients, starting at a low dose to find the optimum dose
a double-blind trial is conducted with patients to eliminate bias and check efficacy
apply to government and international health organisations for permission to market, prescribe and sell the drug
traditionally drugs were extracted from plants and microorganisms:
the heart drug digitalis originates from foxglove
painkilleraspirin originates from willowbark
penicillin was discovered by Alexander Fleming from the penicillium mould which developed a clear ring when growing on a bacterial petri-dish
most new drugs are synthesised by chemists in the pharmaceutical industry, however the starting point may still be a chemical extracted from a plant
new medical drugs have to be tested and trialled before being used to check that they are safe and effective.
new drugs are extensively tested for toxicity, efficacy and dose.