Infection And Response Flashcards
Pathogens
Microorganisms that enter the body and cause disease
Cause communicable diseases in both plants and animals
Bacteria, Viruses, Protists or Fungi
Bacteria
Very small cells (1/100th size of body cells)
Reproduce rapidly inside the body
Make you feel ill by producing toxins that damage the cells and tissues
Viruses
Not cells, much smaller, (1/100th size of bacterium)
Reproduce rapidly inside the body like bacteria
Live inside the cells and replicate themselves using the cells’ machinery to produce many copies of themselves
Cell then bursts releasing all new viruses
Cell damage makes you feel ill
Protists
Eukaryotes
Most single-celled
Some are parasites which live on or inside other organisms and cause damage
Often transferred to organisms by a vector, which doesn’t get the disease itself
Fungi
Some are single-celled
Others have body made up of hyphae (thread-like structures)
Hyphae can grow and penetrate human skin and surface of plants, causing disease
Hyphae can produce spores, which can be spread to other plants and animals
How can pathogens be spreads?
WATER - pathogens can be picked up by drinking or bathing in dirty water e.g cholera- bacterial - spread by drinking water contaminated with diarrhoea of other sufferers
AIR - pathogens can be carried in air and can be breathed in e.g. influenza - virus - caused by airborne pathogens in droplets when someone coughs or sneezes
DIRECT CONTACT - pathogens can be picked up by touching contaminated surfaces, including skin e.g. athlete’s foot - fungus - skin itchy flakes off
Measles
VIRUS
Spread by droplets from infected person’s sneeze or cough
Red skin rash and signs of a fever
Very serious/even fatal if complications
Most people vaccinated against it when young
HIV
VIRUS
Spread by sexual contact or exchanging bodily fluids such as blood
Flu-like symptoms for a few weeks
Virus attacks immune cells
No symptoms for several years - antiretroviral drugs taken during this time
Tobacco Mosaic Virus (TMV)
VIRUS
Affects many species of plants like tomatoes
Causes mosaic pattern on leaves - parts of leaves become discoloured
Discolouration means plant can’t carry out photosynthesis well, so virus affects growth
Rose Black Spot
FUNGAL
Causes purple/black spots to develop on leaves of rose plant - leaves turn yellow and drop off
Stops photosynthesis from happening so plant doesn’t grow very well
Spreads through environment or by wind
Using fungicides and stripping plant of affected leaves which are then destroyed so fungus can’t spread
Malaria
PROTIST
Part of protist’s life cycle takes place inside mosquito
Mosquitos are vectors
Every time mosquito feeds on another animal, it infects it by inserting protist intro animal’s blood vessels
Malaria cause repeating episodes of fever and can be fatal
People can be protected from mosquitoes using insecticides and mosquito nets
Salmonella
BACTERIAL
Type of bacteria causing food poisoning
Suffer from fever, stomach cramps, vomiting and diarrhoea
Symptoms caused by toxins bacteria produce
Eating food that’s been contaminated with bacteria e.g. chicken caught suedes whilst alive, or eating food prepared in unhygienic conditions
Gonorrhoea
BACTERIAL
Sexually transmitted disease (STD)
Caused by bacteria
Pain when urinating, thick yellow or green discharge from vagina or penis
Antibiotics used and so should barrier methods of contraception e.g. condoms
How can the spread of disease be reduced or prevented?
Being hygienic
Destroying vectors
Isolating infected individuals
Vaccination
Body’s defence system
Skin acts as barrier to pathogens - also secretes antimicrobial substances which kill them
Hair and mucus in nose trap particles that could contain pathogens
Trachea and bronchi secrete mucus to trap pathogens - also lined with cilia which waft mucus up to the back of the throats where it can be swallowed
Stomach produces hydrochloric acid that kills pathogens which make out far from the mouth
Three lines of attack from white blood cells
1) Consume
2) Produce antibodies
3) Produce antitoxins
1) Consuming them
WBCs can engulf foreign cells and digest them - phagocytosis
2) Producing Antibodies
Every invading pathogen has unique molecules called antigens on its surface
When some types of WBC come across a foreign antigen they will produce proteins called antibodies with lock onto the invading cells so that they can be found and destroyed by other WBCs
The antibodies produced are specific to that type of antigen
Antibodies are then produced rapidly and carried around body to find similar bacteria or viruses
If the person is infected with the same pathogen again, the WBCs will rapidly produce the antibodies to kill it - the person is naturally immune to that pathogen and won’t get ill
Producing antitoxins
These counteract toxins produced by the invading bacteria
Vaccination
Involves injecting small amounts of dead or inactive pathogens
These carry antigens which cause the body to produce antibodies or attack them - even though the pathogen is harmless
If the live pathogen of the same type appear after that, the white blood cells can rapidly mass-produce antibodies to kill off the pathogen
Pros of Vaccination
Vaccines have helped control lots of communicable diseases that were once common in the UK e.g. polio, measles, whooping cough, rubella, mumps, tetanus
Big outbreaks of disease (epidemics) can be prevented if a large population is vaccinated. That way, even people who aren’t vaccinated are unlikely to catch the disease because fewer people able to pas it on
Cons of Vaccination
Vaccines don’t always work - sometimes don’t give immunity
Can sometimes have a bad reaction to a vaccine e.g. swelling or s maybe something more serious like a fever or seizures. Bad reactions are very rare
