B5: Communicable Diseases Flashcards
How are communicable diseases caused?
They are caused by pathogens and can be passed from one person to another. Pathogens = viruses, fungi, protists, bacteria.
What are viruses?
They are small and cause disease by moving into cells and reproducing inside of them. This may cause them to burst and release copies into the bloodstream. Cell damage is what makes you feel ill.
What is bacteria?
They are small and multiply very quickly by dividing by binary fission. They produce toxins that damage your cells and tissues which makes you feel ill.
What are protists?
They are single celled eukaryotes such as parasites which use humans/animals to live on and cause damage. Usually involve a vector that transfers a pathogen to the host.
What is fungi?
Can produce spores that can spread to other organisms (hyphae). Hyphae can grow and penetrate human skin and the surface of plants, causing disease. Can be fatal if they attack lung/brain of someone who is already ill.
How is disease spread?
Air: Breathing in droplets of air with pathogens, expelled by sneezing/coughing or talking.
Direct Contact: Common in plants. Can be through sexual contact and exchange of bodily fluids. Pathogens can enter body through wounds. Animals can act as vectors and carry pathogens to humans.
Water: Drinking contaminated water, eating undercooked food can mean that pathogens enter the digestive system.
Why are microorganisms grown?
An uncontaminated culture of microorganisms can be grown using sterilised petri dishes. These are needed for investigating the effects of disinfectants and antibiotics. They are incubated at 25°C to reduce the chance of harmful pathogens growing.
Describe how you can carry out an experiment to culture microorganisms.
- The petri dish and agar plate must be sterilised to kill any unwanted microorganisms.
- Clean area you are working in with disinfectant.
- Sterilise inoculating loop using a bunsen burner flame.
- Open petri dish near bunsen burner flame.
- Transfer bacteria to agar plate using inoculating loop.
- If not already, place 3 sterile filter paper discs with antibiotics onto the plate.
- Put lid back on immediately and seal with tape.
- Store upside down to prevent condensation from falling on agar.
- Incubate dishes for few days and observe bacterial growth.
Zone of inhibition = Area that no bacteria has grown
How do bacteria grow?
If bacteria have enough nutrients and a suitable temperature, then they can grow/divide very fast by binary fission. Bacteria x 2^n
How can you limit the spread of pathogens?
- Improve hygiene by washing hands, using disinfectants, using tissues when sneezing.
- Reduce contact with the infected by isolating them.
- Remove vectors by using pesticides.
- Get vaccinations by injecting a weakened form of the pathogen in the blood.
What is measles and how is it spread/prevented?
- Measles is a viral infection and causes fever and red skin rash which can lead to other problems such as lung infection and blindness.
- Spread by inhalation of droplets from sneezes/coughs.
- Can prevented by vaccinating young children. It is less common now due to better living conditions.
What is HIV/AIDS and how is it spread/prevented?
- It is a viral infection that initially causes flu like symptoms and then the virus attacks the immune system and leads to AIDs where the body is susceptible to many different diseases or cancer.
- Spread by sexual contact or exchange of bodily fluids like blood.
- No cure or vaccine but can use antiretroviral drugs.
- Prevented by using condoms and not sharing needles.
What is tobacco mosaic virus and how is it spread/prevented?
- It is a distinctive pattern of discolouration on leaves as virus destroys cells. This affects the growth of the plant as it can’t photosynthesise.
- Spread by contact between diseased/healthy plants, insects can act as vectors.
- Can be prevented by good field hygiene and pest control.
What is salmonella and how is it spread/prevented?
- It is a bacterial disease caused by humans ingesting meat with bacteria in the guts of different animals. It causes fever, cramps, vomiting, diarrhoea caused by the toxins it produces.
- Spread by eating undercooked meat/eggs or if food is prepared in unhygienic conditions.
- Prevented by vaccines, keeping raw meat away from cooked food and generally good hygiene when preparing the food.
What is gonorrhoea and how is it spread/prevented?
- It is a bacterial STD spread by unprotected sexual contact with an infected person.
- It causes yellow discharge from penis/vagina and pain when urinating.
- Prevented by using contraception or using antibiotics however bacteria is becoming more resistant to antibiotics.
What is rose black spot and how is spread/prevented?
- It is a fungal disease that causes purple/black spots to grow on leaves, reducing the area of the leaf available for photosynthesis, causing the leaves to turn yellow.
- Spread by spores of fungus in water or wind.
- Prevented by using fungicides ore removing infected leaves.
What is malaria and how is it spread/prevented?
- Caused by protist pathogens that enter red blood cells and damage them, causing symptoms such as fevers and shaking.
- Spread by vectors of mosquitoes that feed on blood, allowing protist to enter the bloodstream.
- Prevented using insecticide, mosquito nets, antimalarial drugs to kill parasites.
What makes up the human defence system?
Skin: Acts as a barrier by preventing bacteria or viruses from reaching the tissues beneath. Produce antimicrobial secretions to kill pathogens. If cut, platelets quickly form a scab.
Nose: Full of hairs and mucus that trap pathogens breathed in to prevent it from reaching the lungs.
Trachea/Bronchi: Secrete mucus to trap pathogens. Cilia waft mucus upwards to be swallowed.
Stomach: Produces hydrochloric acid to kill pathogens in mucus, food or drink.
How do white blood cells attack pathogens?
Phagocytis/Engulfing Microorganisms - some white blood cells ingest pathogens, digesting and destroying them so that they no longer have an effect.
Produce Antibodies - antibodies target/bind to particular bacteria or viruses and destroy them. If the same pathogen enters the body, antibodies are produced much more quickly, making you immune.
Produce Antitoxins - neutralise toxins released by pathogen by binding to them.
What are common signs of plant diseases?
- Stunted growth (nitrate deficiency).
- Spots on leaves (black spot fungus).
- Areas of decay / Abnormal growths.
- Malformed stems or leaves (aphids).
- Pests on leaves.
- Discolouration (magnesium deficiency).
Why are nitrates important in plants?
They are used to convert sugars from photosynthesis into proteins so a nitrate deficiency stunts growth.
Why is magnesium important in plants?
It is needed to make chlorophyll which is vital for photosynthesis. A magnesium deficiency causes chlorosis.
What are the defence systems of a plant?
Physical: Tough waxy cuticle layer, cellulose cell walls, dead cells around the stem all prevent the invasion of microorganisms.
Chemical: Produce poisons to deter predators, antibacterial chemicals kill bacteria.
Mechanical: Thorns/hairs, may droop or curl when touched, mimicry.
