Defence against Disease and Drugs Flashcards
First Defences : Skin
A physical layer.
Rough top layer sheds, meaning that microorganisms and bacteria shed too.
Sebaceous glands produce antimicrobials.
First Defences : Hair in Nose
Helps trap particles in a sticky layer of mucus ; removed by blowing or swallowing, which is taken care of in stomach
First Defences : Trachea and Bronchi
Hair like projections - cilia
Mucus-producing cells ( goblet cells ) are mixed in with ciliated cells to keep a fresh lining of mucus. This traps large particles + microorganisms. Cilia waft mucus to the back of the throat to be swallowed and microorganisms are destroyed by stomach acid.
Many mitochondria for energy.
First Defences : Stomach
Hydrochloric acid destroys cell wall of microorganisms and kills them ( pH 2 ). Coated with a special lining to prevent the stomach wall corroding.
First Defences : Tears + Eyelashes
Trap dirt and microorganisms, preventing infections.
Tears have high salt content to dry up microorganisms, they also wash out microorganisms.
Lysozyme
Enzyme in tears, breaks down bacterial cell walls.
First Defences : Scabs
Repair physical barrier.
Formed from blood clots - platelets are exposed to the air, making fibrin. This stretches across the wound, forming a mesh. Additional red blood cells and platelets fill the mesh, forming a clot.
Second Defences : Phagocytosis
- Phagocytes leave the blood through capillary walls and enter blocked tissue.
- Cell membrane and cytoplasm of the phagocyte surrounds the pathogen.
- Pathogen is engulfed by phagocytosis.
- Pathogen is digested by lytic enzymes. Useful substances are absorbed and waste substances are released via exocytosis. The phagocytes can continue to engulf more pathogens.
Pathogen
A microorganism that causes disease.
Third Defences : Lymphocytes
Lymphocytes produce antitoxins to neutralise the toxins from pathogens, making them safe. Antitoxins are specific to particular toxins.
Antibody
A protective protein produced by the immune system (WBCs - phagocytes) in response to the presence of a foreign substance, called an antigen. They recognise and latch onto antigens in order to remove them from the body. They can either neutralise the pathogen by binding or initiate phagocytosis.
Antigen
An antigen is a substance that is capable of stimulating an immune response. Often on the surface of a pathogen but can also be a toxin or a chemical.
Vaccination
Involves introducing small quantities of dead or inactive forms of a pathogen into the body to stimulate the WBCs to produce antibodies. If the same pathogen re-enters the body, the WBCs respond quickly to produce the correct antibodies, preventing infection.
Response to vaccine
Primary response : 1st exposure, correct antibodies made over 2-3 weeks
When pathogen destroyed, conc. of antibodies decrease, but not to zero due to memory cells ( WBCs that stay in your blood and remember how to make pathogen specific antibodies ) created
Secondary response : 2nd exposure - more antibodies created faster due to memory cells - no symptoms, not ill
Small pox
A virus.
Cure found by Edward Jenner, who inoculated James Phipps with cowpox pus, which helped develop memory cells, which also fought smallpox as they were in a similar viral family.
Issues with vaccines
Pathogen could mutate.
Not everyone will want to be vaccinated.
Side effects eg fever, chills, muscle pain, headache.
Herd immunity
Mass vaccination programmes increase the number of people who are immune, making it harder for the pathogen to spread to nonimmunised people.
Global vaccination problems
LICs have less access to healthcare.
Funding.
How the vaccine is rolled out - focus on densely populated areas
Drug
Any chemical that alters how the body works.
Main goals of medicines
Relieving symptoms.
Breaking / curing the underlying illness by destroying pathogens.
Antibiotics
Only kill bacterial pathogens.
1. Interfere with a pathogens metabolism eg. prevent cell wall growth or block the actions of ribosomes ( cannot grow ).
2. Slow bacterial growth long enough for the immune system to get on top of them.
Don’t harm our own cells.
Specific bacteria have to be treated with specific antibiotics, however, there are some general ones eg. amoxicillin.
Alexander Fleming
Discovered penicillin ( fungal mould )
He was investigating a strain of bacteria called Staphylococcus, growing them on petri dishes. He came back from holiday to find mould had contaminated one of his petri dishes, but there was no bacteria growing around it. He concluded that the mould must make a chemical that destroys the bacteria.
Name originated from the mould’s family, Penicillum.
Antibiotic resistance
Mutation in DNA of bacteria, making it resistant to antibiotics. This mutated cell continues to divide by binary fission, creating a drug-resistant population.
Reducing antibiotic resistant strains
Doctors should not prescribe antibiotics inappropriately.
Patients should complete a full course of antibiotics, so none survive, therefore can’t mutate.
Widespread agricultural use.
Common antibiotic resistant strains
Antibiotic-resistant gonorrhea
MRSA ( a hospital superbug )
Painkillers
Stop nerve impulses transmitting pain messages to the brain, therefore limiting the feeling of pain.
Mainly based on - aspirin, opiates ( from poppies )
In the past, drugs were extracted from plants :
Foxglove provides heart drug, digitalis.
Willow bark provides aspirin.
Penicillin from penicillum mould.
Antiviral drugs
Slow down viral development.
Hard to manufacture a drug to kill a virus as they reproduce inside cells.
Preclinical drug testing - Laboratory
Tests using computer models and human skin cells ( grown from stem cells ). Can test effectiveness and side effects.
Fails if drug damages cells.
Preclinical Drug testing - Animal
Continues to test for effectiveness, but also monitors side effects. Variety of animals used, but try to show relatedness to humans.
Clinical drug testing
Phase 1 - healthy people, 20-80 volunteers (for safety and dosage)
Phase 2 - infected people, 100-300 volunteers (for efficacy and side effects)
Phase 3 - 3000+ volunteers, Double blind tests (Patients are randomly allocated into groups, one has drug, one has placebo), peer review (research checked by other experts for validity + ethics, before publication in scientific journals)
Phase 4 - Doctors report on side effects - continues as long as medicine in circulation
Placebo effect
People feel better as they believe they are taking the drug
Monoclonal
All one type, MABs are copies of one type of antibody
Lymphocytes cannot
divide after they begin to produce antibodies
Method of making MABs
Mouse is injected with specific antigen to stimulate lymphocytes to make specific antibody.
Extracted lymphocytes are combined with a specific tumour cell. Detergents used to break cell membranes and help fuse.
Creates a hybridoma cell, which can divide and make antibodies.
Screened to check for antibody production.
Cloned to produce identical cells that produce same antibody ( these are MABs )
Large amount of MABs are collected and purified.
Pregnancy tests
rely on monoclonal antibodies which bind to HCG, a hormone made in the early stages of pregnancy.
MAB research use
Can carry fluorescent markers, which make it easy for doctors to see where they have built up. When the antibody binds to the specific antigen, it will fluoresce. This allows doctors to detect problems before they seriously affect a person’s health.
Antiseptic
A chemical that destroys pathogens outside the body.
Parts of a pregnancy test
The reaction zone contains MABs, specific to HCG, with an enzyme attached that can activate dye molecules.
The results zone contains immobilised MABs specific to HCG.
The control zone contains immobilised antibodies complementary to the MABs from the reaction zone.
How a pregnancy test works
When a pregnant woman’s urine touches the reaction zone, HCG will bind to the MABs.
As urine moves up the test, MABs, + their associated enzymes, are stopped in the results zone, as the MABs here also bind to HCG. The enzymes activate the dye, creating a blue line.
Antibodies, + associated enzymes, not bound in the results zone move up into the control zone, where they bind to the immobilised antibodies. The enzymes react with the dye to show a second blue line.
Pregnancy test if not pregnant
The free MABs will be stopped ONLY in the control zone, showing one blue line.
MABs treatment use
- an anti-cancer drug is attached to a monoclonal antibody ; the MABs bind to specific antigen on the cancer cell ; drugs either directly destroy cancel cell, or prevent cells from dividing and growing ; harmless to surrounding tissue.
- Once bounds, trigger immune system to attack and destroy the cancer cells.
- Make cancerous cells more identifiable to surgeons eg. clumping together or fluorescence.
MAB treatment advantages
Healthy cells are unaffected
Side effects easily treated
Treat wide range of conditions
Used in many different ways
MAB treatment disadvantages
Expensive
Many side effects eg. nausea, fever
Difficult to get correct antibodies
Ethical issues
Antiseptic RQP variables
independent - type of antiseptic
dependent - area of uninfected circle
control - type of bacteria, volume of antiseptic, type of agar jelly, temperature
Zone of inhibition
Area where no bacteria is growing
Antiseptic RQP method
1.Wash hands to prevent contamination
2.Draw quarters onto petri dish and label each quarter with type of antiseptic.
3.Use a sterile pipette to add 100 microlitres of microbial culture to agar jelly. Keep lid as closed as possible throughout to prevent air microbes entering.
4. Sterilise a spreader by dipping in ethanol to kill bacteria, passing through a flame and allowing to cool.
5.Use spreader to gently spread microbial culture across the agar jelly.
6.Sterilise forceps.
7.Use forceps to soak a mast ring in an antiseptic and place in labelled quarter of petri dish.
8. Repeat 7 for each antiseptic.
9.Tape plate shut to prevent microbes from the air entering.
10.Wash hands.
11. Incubate at 25C for a week.
12. Measure diameter of zone of inhibition.
3. Calculate areas.
