Infection & Response

• What are considered microorganisms?

  • Viruses 
  • Fungi
  • Protists
  • Bacteria 
• What is a pathogen?

  A microorganism that can cause a communicable disease 

  • It can infect both animals and plants
• What are the four main ways a pathogen can spread

  • Through the air - Diseases such as influenza and measles can spread via tiny droplets of saliva that we expel when we cough or sneeze.
  • Contaminated water - Diseases such as cholera can spread through water sources contaminated by the diarrhoea of infected people. 
  • Contaminated food - Diseases such as salmonella are spread by eating food which has been infected with salmonella, and then not cooked properly.
  • Direct contact - Athlete's foot is spread by walking barefoot on surfaces contaminated with the fungi. 
• Give four ways we can reduce the spread of infectious diseases?

  • Improved hygiene, such as washing hands and cleaning surfaces 
  • Vaccination 
  • Killing the vectors that carry pathogens 
  • Isolating or quarantining people who are infected 
• Viruses are not living organisms or made up of cells

  • They are about 10,000 times smaller than animal or plant cells. 
• • Viruses can pass between humans via the air, contaminated food or water, or by direct contact.
  • As they can't reproduce themselves, viruses have to enter one of our cells, and then use it to create multiple copies of the virus itself.
  • Once there are lots of copies, the viruses cause the cell to burst, and then go on to infect neighbouring cells. 
• What are three types of viruses?

  • Measles
  • HIV
  • Tobacco mosaic virus
• Measles

  Symptoms: Fever, red skin rash

  Transmission: droplets in air when an infected person coughs or sneezes

  Control of spread: Childhood vaccinations
• HIV

  Symptoms: Flu like symptoms for two weeks, then serious damage to the immune system

  Transmission: Sexual contact and exchange of bodily fluids

  Control of spread: Anti-retroviral drugs, use of condoms, Don't share needles
• Tobacco Mosaic Virus

  Symptoms: Mosaic Patten on leaves

  Transmission: Enters via wounds in epidermis caused by pests

  Control of spread: Remove infected leaves and control pests that damage leaves
• HIV stands for Human Immunodeficiency Virus.

  This is because it affects humans, it weakens the immune system (immunodeficiency), and it is a virus. 
• Infection with the HIV virus can lead to ADIS. This is where the immune system is so weak that the person can catch unusual infections. 
• Tobacco Mosaic Virus (TMV) reduces the amount of photosynthesis that a plant can do.
• Bacteria are unicellular
• Only a small minority of bacteria cause disease. Lots of bacteria don't affect other organisms at all, while many others are actually helpful.
• Bacteria release small proteins called toxins. These can damage our cells and are responsible for many of the symptoms of bacterial diseases. 
• What are two types of bacteria?

  • Salmonella
  • Gonorrhoea
• Salmonella

  Symptoms: Fever, stomach cramps, vomiting, diarrhoea

  Transmission: Food prepared in unhygienic conditions or not cooked properly

  Control of spread: Improve food hygiene, wash hands, cook food thoroughly, vaccinate poultry

  Treatment: hydrate well and symptoms should pass within a week
• Gonorrhoea

  Symptoms: Green discharge from the vagina or penis, pain when urinating

  Transmission: Direct sexual contact or exchange of bodily fluids

  Control of spread: Use condoms

  Treatment: Antibiotics
• Fungi can be either unicellular or multicellular
• What is a example of a fungal disease?

  • Rose black spot
• What is an example of a protist disease?

  • Malaria
• Rose black spot

  Symptoms: Purple or black spots on leaves, reduced photosynthesis

  Transmission: Spores carried by wind or water

  Control of spread: Remove infected leaves

  Treatment: Spray with fungicides
• Malaria

  Symptoms: Recurrent fever, headaches and in extreme cases it can be fatal

  Transmission: By an animal vector (mosquitoes)

  Control of spread: Prevent breeding of mosquitos, use mosquito nets and bug spray
• Protists are considered parasites. This means that they live on, or in, a host organism, and get their food at the expense of their host.
• What's a vector?

  An organism that transport a disease to another organism without being infected
• What are ways we can reduce the spread of malaria?

  • Stop the mosquito vectors from spreading the protists 
  • Destroy the mosquito breeding sites 
  • Use mosquito nets
  • Use mosquito repellent 
• What is an antigen and what are examples?

  An antigen is any substance that your body sees as foreign, which then causes your immune system to produce antibodies against it.

  • the toxins and cell walls of pathogens would be considered antigens. 
• What an antibody?

  An antibody on the other hand is a protein produced by our white blood cells that binds to specific antigens. This acts as a signal to our immune system to destroy the antigen/pathogen
• What are examples in our body that reduce the entry of pathogens?

  • Enzymes in tears
  • Hairs/mucus in the nose
  • Skin/skin oils
• How does skin help to defend against disease?

  • It covers the body, physically preventing pathogens from entering
  • It secretes oils and antimicrobial substances that kill pathogens
• What substance does the stomach produce to kill pathogens? 

  Hydrochloric acid 
• The cells that line the trachea, bronchi and bronchioles have tiny hair-like projections (cilia) that waft the mucus and pathogens away from the lungs. 
• What is the role of the immune system?

  To locate and destroy pathogens that enter the body
• What are three functions of white blood cells

  • Producing antibodies 
  • Phagocytosis 
  • Produce antitoxins 
• Stages of phagocytosis

  1. Phagocytosis is carried out by a special type of white blood cell called a phagocyte. 
  2. The first step is for the phagocyte to track down a pathogen, and then bind to it. 
  3. The phagocyte's membrane will then surround the pathogen and engulf it.
  4. Finally, enzymes inside the phagocyte break down the pathogen in order to destroy it.
• What do antitoxins do?

  Bind and neutralise the toxins produced by bacteria 
• What does a vaccine contain?

  Small quantities of dead, weakened, or inactive forms of a pathogen
• vaccines be made against both bacterial and viral diseases
• How do vaccines work?

  They expose us to the antigens of a pathogen so that we can develop immunity to it

  -The memory cells can produce antibodies straight away if the person becomes infected so they don't feel any symptoms