Infection and response summary - year 9 biology

Pathogens

Pathogens

a disease-causing micro organism, there are four types: virus, bacteria, fungi and protist, they infect a host to cause communicable diseases, these diseases can be spread through direct contact, water, air, vectors and unhygienic food preparation

Viruses

are not alive because they do not complete (MRS GREN), made from short lengths of DNA with a protein coat, they infect a suitable host (then replicate themselves until the host cell burst), can't be treated with anti-biotics

Tobacco mosaic virus

infects tobacco and tomatoes, transmitted through contact between plants, infects the chloroplasts which changes the leaves' colour and reduces photosynthesis, there is no cure

HIV/AIDS

a virus transmitted through bodily fluids/sharing needles/cuts, people suffer flu-like symptoms which pass, after a while HIV becomes AIDS which attacks the patient's immune system, there is no cure but infected people are given anti viral drugs to slow AIDS development

Measles

a virus transmitted through droplets in the air, which causes a fever and skin rashes, children are vaccinated to prevent it

Bacteria

are prokaryotic cells, not all bacteria are pathogens

Gonorrhoea

an bacterium STD, causes yellow/green discharge and pain whilst urinating, prevented by using barrier methods (condoms), can be treated by antibiotics

Salmonella

a bacteria that causes food poisoning which leads to stomach cramps and vomiting, found in undercooked meat or eggs, farm animals are vaccinated against it, prevented by fully cooking food in hygienic places/surfaces

Protists

eukaryotic micro organisms which share some features with plants/animals

Malaria

is a protist spread by vectors (mosquitos), they suck blood from infected people and then pass it on to others they bite, symptoms include a fever headaches sweats and vomiting, there is no vaccine but people spray insect repellent and sleep under mosquito nets, and antimalarial drugs can be taken to treat symptoms

Fungi

are eukaryotic micro organisms

Athlete's foot

a rash caused by fungi, causes red/flaky or white/wet skin, is transmitted in communal areas (swimming pools), treated by antifungal medication

Rose black spot

caused by a fungus, causes purple/black spots on plant leaves and can make other leaves drop off, reduces it's ability to photosynthesize, transmitted through water/air/direct contact, treatable using fungicides

First line of defence

skin (heals itself when cut to stop pathogens entering body) eyes (produce tears which are chemical barriers) nose (hairs act as a physical barrier, cells in the nose produce mucus which traps pathogens) trachea and bronchi (cells line the trachea with hair known as cilia which waft their hair and move mucus, which traps pathogens and is then swallowed) stomach (stomach acid kills pathogens that have been swallowed)

Phagocytes

engulf pathogens and enzymes inside break it down, they do this to all pathogens so are 'non-specific'

Lymphocytes

a type of white blood cell that recognize antigens, produce antibodies which cause pathogens to stick together (makes it easier for phagocytes yo engulf), can also produce antitoxins if pathogens produce toxins, antibodies and antitoxins are specific to the pathogen

Vaccines

contain a specific antigen, causes immune system to create complementary antibodies, when a majority of a population is vaccinated this can lead to herd immunity

Painkillers

can relieve symptoms but don't cure the disease

Antibiotics

slow down/stop growth of bacteria but don't work for viruses, they kill bacterial cells but not host cells ,the first antibiotic was discovered by Alexander Flemming in 1928, they are becoming less effective due to antibiotic resistance increasing because of overuse of antibiotics

Drug development

drugs must be tested for safety, effectiveness and dosage, they are first tested on human cells in a lab (then animals, and finally healthy human volunteers and infected human volunteers)