Flashcards in B3 Infection and Response Deck (41):
What is a pathogen?
A pathogen is a microorganism that causes disease
How are pathogens spread?
Water, air (droplets), direct contact and contaminated food or water
How can the spread of pathogens generally be prevented?
Good hygiene, destroying vectors, isolating infected individuals, vaccination, cooking and clean water
What are bacteria?
- Very small cells (1/100th of a body cell)
- Produce toxins that damage cells and tissues
Communicable disease examples: Salmonella
- Bacterial disease
- Caused by undercooked food or eating contaminated food with the Salmonella bacteria
- Causes fever, stomach cramps, vomiting and diarrhoea
- Prevented by cooking food, good hygiene and vaccinating poultry
- In the UK, poultry are vaccinated against Salmonella to control the spread
Communicable disease examples: Gonorrhoea
- Bacterial disease
- Spread by sexual contact (unprotected sex)
- Symptoms include yellow/green discharge from genitals and pain when urinating
- Prevented by condoms or antibiotics (penicillin)
What are viruses?
- Not cells
- 1/100th size of a bacterium
- reproduce rapidly
- replicate themselves within body cells and eventually burst out releasing more virus cells and cell damage (making us ill)
Communicable disease examples: Measles
- Viral Infection
- Caused by droplets from the air (sneezing or coughing)
- Symptoms include fever, rash and blindness
- Complications from pneumonia and encephalitis can lead to brain damage or be fatal
- Most children are vaccinated against it
Communicable disease examples: HIV
- Viral Infection
- Caused by contact with bodily fluids (sexual contact, blood, sharing needles)
- There are initial flu-like symptoms with HIV then become symptomless for many years
- Late HIV stages or AIDS occurs when the body's immune system becomes so damaged that the body can't cope with other infections or cancers
- HIV can controlled with antiretroviral drugs
- Can be prevented with condoms, blood screening, not sharing needles
Communicable disease examples: TMV
- Tobacco Mosaic Virus is a viral infection in plants
- Caused by the contact with insect vectors carrying the virus
- Causes a mosaic pattern on the leaves (becoming discoloured), plant can't carry out photosynthesis and therefore growth is affected
What is fungi?
- Some are single-celled and others have a body made up of hyphae
- Grow and penetrate human skin/surface of plants
- Produce spores to spread to other plants and animals (wind + water)
Communicable disease examples: Rose Black Spot
- Fungal infection in plants
- Causes purple/black spots on plants, reducing photosynthesis, leaves eventually turn yellow and drop off
- Prevented by the removal/burning of infected leaves or using fungicide sprays
What are protists?
- All eukaryotes and mostly single celled
- They're parasites that live in or on other organisms causing damage
- Transferred between organisms by vectors (e.g. insects)
Communicable disease examples: Malaria
- Protist disease
- Caused by mosquito bites as it inserts the protist into the blood vessels
- Part of the mosquitoes life cycle
- Mosquito are vectors - catch it from feeding on infected animals
- Symptoms include: recurrent fever (when pathogens burst out of liver and red blood cells) and fatal
- Prevented by anti-malarial drugs, preventing the breeding of mosquitoes, mosquito nets and removal of stagnant water (where they breed)
Describe the body's non-specific defence systems
- Skin acts as a barrier and secretes antimicrobial substances
- Hairs and mucus in the nose trap particles which may contain pathogens
- Trachea and bronchi (lungs) secrete mucus to trap pathogens, walls are lined with cilia (hairs) which waft mucus back up to the back of the throat to be swallowed, stomach produces hydrochloric acid, killing any pathogens
What is the role of the immune system?
If a pathogen enters the body the immune system tries to destroy the pathogen
Describe how white blood cells destroy pathogens
White blood cells help to defend against pathogens by:
• recognise foreign cell (from antigen) and engulf the cell, enzymes inside will render it harmless
2. antibody production
• antibodies are made and released by WBC which are specific to a cell's antigen, joins to the pathogen's antigen, clumping multiple together allowing white blood cells to engulf pathogen
• counteract the toxins of the bacteria
What is an antibody?
Antibodies are proteins that bind to antigens to damage pathogens or clump them together
What is meant by being naturally immune?
- WBC can recreate an antibody quicker and at larger quantities if the pathogen re-enters the body as they know what antibody fits to which antigen
What is meant by artificial immunity?
Getting white blood cells to respond to a particular pathogen without harm
Describe how vaccines work
1. Injected with a dead/inactive virus
2. WBC are stimulated to create the correct antibodies fro the antigen of that pathogen
3. Antibodies clump pathogens together to be engulfed
4. The next time the pathogen re-enters the body (artificially or naturally), the WBC respond quicker, release larger quantities of antibodies and they stay in the blood longer to prevent infection
What is meant by herd immunity?
When a large number of people in a population are immune (less people pass on the disease)
Discuss Pros and Cons of vaccines
• Able to control once common and fatal communicable diseases
• Epidemics are prevented from herd immunity as less people are able to pass it on
• In rare cases it doesn't give an individual immunity
• In rare cases there are bad reactions, fevers, seizures or swelling
How are painkillers and antibiotics used to treat diseases?
- Painkillers are drugs that relieve pain, reduce symptoms but DON'T fight the disease (decongestants also treat symptoms)
- Antibiotics are drugs that kill or prevent growth of a specific type of bacteria
Explain how antibiotic resistant can be prevented
Bacteria has mutated causing antibiotic resistance which can cause serious infections that can't be treated, e.g. MRSA is resistant to the powerful antibiotic meticillin
To stop this from happening:
• doctors should avoid over-pescribing
• increase the importance on finishing the whole course of antibiotics
Describe the sources of drugs
• Aspirin (lowers fever) -> willow
• Digitalis (treats heart conditions) -> foxgloves
• some are extracted from microbes
* (for example) Flemming found that the mould penicillin notatum produced a substance that killed the bacteria penicillin
Describe how drugs are tested
New drugs have to be tested for toxicity, efficacy and dose
1. Pre clinical trials on human cells and tissues
• can't show how it would affect a whole body system
2. Pre clinical trials on live animals
• testing efficacy, toxicity and to find an optimum dosage
• In the UK drugs must be tested on 2 different mammals before human trials
3. Clinical Trials on human volunteers
• Small group of healthy volunteers -> harmful side effects and optimum dose
• Small group of volunteers with disease -> efficacy?
• Large group of volunteers with disease -> long term effects?
4. Peer reviewed (prevents false claims)
What is a blind trial?
Where the patient doesn't know if they're in the control group of placebo, but the group collecting the data does know, leading to possible bias
What is a double blind trial?
Neither the patient or doctor knows what group the patient is in, removing bias
- Pharmaceutical company outsources drug trial to an independent company to eliminate bias completely as they're not being paid
What is a placebo?
A medicine that does not contain the active drug being tested
What are the uses more mABs?
• for diagnosis such as in pregnancy tests or detecting STDs
• in laboratories to measure the levels of hormones and other chemicals in blood, or to detect pathogens
• in research to locate or identify specific molecules in a cell or tissue by binding to them with a fluorescent dye
• to treat some diseases: for cancer the monoclonal antibody can be bound to a radioactive substance, a toxic drug or a chemical which stops cells growing and dividing by preventing the growth hormone from binding. It delivers the substance to the cancer cells without harming other cells in the body.
How are mABs used in pregnancy tests?
- HCG hormone found in the urine of pregnant women
- Antibodies are attached to blue-dye which binds the hormone at the end of the stick (from urine)
- Hormones with the blue dye stick down to the antibodies in the result window, forming a visible blue strip
- Leftover antibodies with blue dye travel further up and bind to stuck down antibodies in the control window turning it show, forming a visible blue line to show it worked
How are mABs produces?
- They are produced by stimulating mouse lymphocytes to make a particular antibody from injecting a mouse with an antigen. The lymphocytes (found in large quantities within the spleen) are combined with a particular kind of tumour cell to make a cell called a hybridoma cell.
-The hybridoma cell can both divide and make the antibody.
- Single hybridoma cells are cloned to produce many identical cells that all produce the same antibody. A large amount of the antibody can be collected and purified
Discuss advantages and disadvantages of mABs
• specific -> don't effect any other healthy cells, unlike chemotherapy that can damage things like cells in the digestive tract and cause hair loss
• Can be attached to toxic chemicals/radiation emitting chemicals
• more side effects (fever, vomiting, low blood pressure)
• expensive to produce
• can be difficult to attach to chemicals/subtances
Describe the visible signs of plant disease (and their causes)
- Yellowing of the leaves -> virus TMV
- Black spots of the leaves -> fungi rose black spot
- Crown galls (tumour like collection of cells forming on plant) -> bacteria, agrobacteria tumefaciens
- Chlorosis (yellow leaves -> mineral deficiencies, magnesium ions are needed for making chlorophyll for photosynthesis, so plants w/o Mg ions have yellow leaves
- Stunted growth -> lack of nitrates, nitrates are needed fro protein synthesis, which are used for growth
- Aphids (pests):
• can pierce through phloem vessels and drink cell sap (plants sugars) which starves the plant
• breaking this barrier can also expose the plant to infections or aphids themselves can act as vectors carrying and passing on the virus
What are the general signs of plant diseases?
- stunted growth
- abnormal growth
How can plant diseases be prevented?
- early intervention
- removing diseased plant(s)
How can plant diseases be identified?
- gardening manual/website
- testing plant in a lab
- testing kits identifying pathogen with mABs
What are some plant physical defences?
• Cellulose cell walls
• Tough waxy cuticle on leaves
• Layers of dead cells around stems (bark on trees) which fall off
(all barriers to pathogens entering)
What are some plant chemical defences?
• Antibacterial chemicals (e.g. witch hazel)
• Poisons to deter herbivores