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Defending Against Infection (Medicine (Antibiotics are substances that…
Defending Against Infection
White Blood Cells
white blood cells do not eat the pathogens - they ingest them
antibodies and antitoxins are not living things - they are specialised proteins
The pathogens are not the disease they cause the disease
Ingest pathogens and destroy them.
Produce antitoxins that counteract the toxins released by pathogens.
The pathogens are not the disease - they cause the disease
Antibodies
Bind to pathogens and damage or destroy them
Coat pathogens, clumping them together so that they are easily ingested by white blood cells called phagocytes
Antibodies are proteins
Each lymphocyte produces a specific type of antibody
Vaccines
These all act as antigens. When injected into the body, they stimulate white blood cells to produce antibodies against the pathogen. If the person does get infected by the pathogen later, their body can respond in the same way as if they had had the disease before
Live pathogens treated to make them harmless
Harmless fragments of the pathogen
Dead pathogens
Medicine
Antibiotics are substances that kill bacteria or stop their growth. They do not work against viruses because they live and reproduce inside cells. It is difficult to develop drugs that kill viruses without also damaging the body’s tissues
Penicillin breaks down cell walls
Erythromycin stops protein synthesis
Ciprofloxacin stops DNA replication
Painkillers helps to relieve the symptoms of an infectious disease, but they do not kill the pathogens involved
Bacterial strains can develop resistance to antibiotics. This happens because of natural selection
The main steps in the development of resistance are:
antibiotics kill individual pathogens of the non-resistant strain
resistant individual pathogens survive and reproduce
the population of the resistant pathogens increases.