b3- infection and response

• pathogens are-

  • microorganisms that enter the body and cause disease
  • they cause communicable diseases
  • both plants and animals can be infected by pathogens
• bacteria are-

  • very small living cells
  • they make you feel ill by producing toxins that damage your cells and tissues
• viruses are-

  • not cells, they're much smaller
  • they reproduce rapidly inside your body
  • they live inside your cells and replicate themselves to make many copies before they burst releasing all of the new viruses
  • the cell damage makes you feel ill
• protists are-

  • single celled eukaryotes
  • some protists are parasites, they live on or inside other organisms and can cause them damage
  • they are often transferred to the organism by a vector
• fungi-

  • come in different shapes- some are single celled
  • others have a body made of hyphae (thread-like structures)
  • these hyphae can produce spores which can be spread to other plants and animals
• pathogens can be spread by-

  • water: drinking/bathing in dirty water cause diseases like chloera
  • air- pathogens can be carried in the air and then breathed in, some can be spread by coughing/sneezing
  • direct contact- touching contaminated surfaces can spread things like athletes foot
• viral diseases-

  • measles : spread by droplets, causes a red skin rash + fever, can be fatal, most people are vaccinated against it
  • HIV: spread by sexual contact/ exchanging bodily fluids, initially causes flu-like symptoms for a few weeks then none for several years. can be treated with antiretroviral drugs- develops into aids
  • TMV: affects many species of plant, causes leaves to become discoloured affecting the rate of photo synthesis
• fungal disease-

  • rose black spot: causes black spots on plants which causes leaves to then turn yellow and drop off
  • this means less photosynthesis can happen and the plan therefore doesn't grow very well
  • gardeners can treat the disease using fungicides and by stripping the plant of its affected leaves
  • those leaves then need to be destroyed to prevent further spread of disease
• disease caused by protist-

  • malaria: causes repeating episodes of fever and can be fatal.
  • spread of malaria can be reduced by stopping the mosquitos from breeding and using insecticides/ mosquito nets
• bacterial diseases-

  • salmonella: causes food poisoning- fever, stomach cramps, vomiting and diarrhoea, cause by the toxins bacteria produce. you get salmonella from eating contaminated food and this can be prevented by vaccinating poultry
  • gonorrhea (STD) : passed on by sexual contact and causes pain when urinating, discharge. treated by antibiotics + prevented by barrier contraceptives such as condoms
• spread of disease can be prevented by-

  • being hygienic (washing hands)
  • destroying vectors (using insecticides ect.)
  • isolating infected individuals
  • vaccination
• defence systems-

  • skin: acts as a barrier, secretes antimicrobial substances that kill pathogens
  • hairs + mucus: trap particles that contain pathogens
  • trachea + bronchi: secrete mucus to trap pathogens
  • trachea + bronchi: lined with cilia
  • stomach: produces hydrochloric acid that kills pathogens
• phagocytosis- white blood cells can engulf and digest foreign particles
• producing antibodies-

  • every invading pathogen has antigens on its surface
  • when some types of WBC come across a foreign antigen, they produce antibodies to lock onto the invading cells so that they are found and destroyed by other cells
  • anti bodies are then produced rapidly and carried around the body to find all similar bacteria or viruses
• producing antitoxins-

  • anti-toxins are produced to neutralise toxins produced by bacteria
• vaccination-

  • small amounts of dead or inactive pathogens are injected into the blood stream.
  • these carry antigens which cause your white blood cells to begin phagocytosis and find the correct antibody.
  • B-memory cells remember the antibody, and if your body ever becomes infected again youre now immune
• painkiller- relieve symptoms
• antibiotics- kill/prevent growth of the bacteria without killing your own body cells
• antibiotic resistance- bacteria can mutate which can cause them to be resistant to an antibiotic

  • superbugs can develop and are more prevalent in hospitals
  • to prevent this make sure to take the full course of anti biotics
• aspirin-

  • found in willow is used as a painkiller to lower fever
• digitalis-

  • found in foxgloves and is used to treat heart conditions
• penecillin-

  • discovered by alexander fleming, comes from mould
• drug testing-

  • preclinical trials: human cells + tissues are tested on in a lab
  • live animals to test for efficancy, dosage, toxicity
  • healthy human volunteers
  • ill people
• double-blind trials-

  • where neither the doctor or patient knows which is the drug and which is the placebo.
  • this prevents sub-conscious bias