biology test revision

pathogen: microrganism (animals, plants, fungi, protists, prokaryotes) that causes disease

physical barrier: first line of defense, EG: skin, mucus, cillia

skin: stops nearly all pathogens entering the body

mucus and cillia: goblet cells secrete mucus which traps dust and pathogens, ciliated epithelial cells brush up the mucus to the top of the trachea. the mucus is swallowed and ends up in the stomach acid wich kills majority of pathogens.

chemical barriers: glands in the skin secrete lysozymes which are enzymes that break down bacterial cell walls.

lysozymes found in:

• tears-protects eyes
• saliva-protects mouth
• mucus-protects nasal passage, respiratory and reproductive systems.

specialised cells in the stomach secrete hydrochloric acid, ph2, which dentaures proteins which kills most pathogens.

• some pathogens are adapted to surviving the lysozymes and pHs of vaginal fluids and mucus, these pathogens can therefore be transmitted or passed through people through intercourse/contact.
• examples: chlamydia (bacteria), HIV (virus) 
• can be stopped by physical barriers or abstinence
• many STIs can also be transferred via blood, allowing them to be pased between pregnant mothers and their unborn child or people thats hare needles.
• for this reason all blood donations have to be sceened before being used.

phagocytes:

• white blood cells attract pathogens. surround the pathogen in blood and bind the them and engulf them. the membrane surrounds the pathogen and the enzymes inside destroy the pathogens.

lymphocytes:

• white blood cells that recognise antigens and produce interlocking antibodies which make it easier for the phagocytes to engulf them.
• a specific type of lyphocyte called a memory lymphocyte which can recognise the antigens from previous pathogens so a second immune response would be much faster.

immunisations allow an inactive form of the disease causing a pathogen to be introduced to the body which causes the immune system to produce complementary antibodies which make the person 'immune' to the disease if they end up getting it becasue they would have memory lymphocytes.

herd immunity: protection given to a population against an outbreak of a specific disease when a high percentage have been vaccinated against it. this results in protection to a larger crowd against disease.

memory cells: 

• 1. when a white blood cell is selected by binding to an antigen it makes thousands of copies of itself.
• 2. many of these become antibody producing cells which die shortly after the infection has cleared
• 3. however, some become memory cells that live many years even a lifetime, these circulate the body in case the same pathogen shoukd attack again.

secondary response: steeper gradient faster rate of response, more antibodies produced, little lag time

antibodies: are proteins produced by white blood cells(lymphocytes) and which bind with extremely high efficiency to specific antigens. all living things have antigens on their surface therefore with the right antibody you can target any cell you want.

monoclonal antibodies are antibodies orginated from clones of a single lymphocyte.                                                                                                     if you want highly specific antibodies which are all identical you have to obtain them from the same white blood cells however fully differenciated cells like lymphocytes do not divide, they hace many uses like pregnancy testing, locationg blood clots/cancer cells, targeting specific cells.

hybridoma cells 

stage 1: a particular antigen is injected into a mouse which produces lymphocytes that make antibodies against the particular antigen. also a cancel cell is growing in culture medium

stage 2: the lymphocyte from the mouse and cancer cell is produced, and they fuse to form a hybridoma cell, these hybridoma cells divide and produce millions of monoclonal antibodies specific to the original antigen. The hybridoma cells have the characteristics of both the lymphocyte in producing antibodies and the cancerous cell in the ability to divide over and over again.

stage 3: the hybridoma cell can divide AND make antibodies against the particular antigen, these are monoclonal antibodies. these monoclonal antibodies are then used to make indefinte amounts of antibodies for said things specific to the chosen antigen

pregnancy tests use monoclonal antibodies, these have been designed to bind with a hormone called HCG which is found only in the urine of pregnant women. Monoclonal antibodies are attached to the end of a pregnancy test stick onto which a woman urinates. If she is pregnant, HCG will be present in her urine and will bind to the monoclonal antibodies on the test stick. This will cause a change in colour or pattern which will indicate pregnancy. These specific monoclonal antibodies in the pregnancy test will only bind with HCG.

monoclonal antibody attactched with radioactive material, then when the antibody attaches to a tumour cell, a scan is taken so the scan detects the radioactivity which can pinpoint cancer cells/tumours.

chemotherapy and radiotherapy kill all cells, they are non specific so either the cancer cells die first and the patient is healthy or too many healthy cells die and the patient dies, so new technology has been trying to target specifically cancer cells so monoclonal antibodies can deleiver the anti-cancer drugs directly.

method:

• set up equipment and let the bunsen burner heatthe air around to make a sterile area (blue flame) 
• mark the agar plate into 3 sections, write on side of dish; name, initials, bacteria
• use a sterile pipette and flame the neck of the bottle before and after use, open lid of agar plate 45 degrees and put in the bacteria then use a sterile spreader and spread the bacteria around
• then put spreader and pipette into virkon bottle to disinfect.
• in the agar plate, a lawn of bacteria will grow.
• 3 types of antibiotic are then put on a disk pmarked in 3 by sterile tweezers (+ a control)
• incubate for 24 hours and see which antibiotic would work best.

results: 

there should be 3 circles with bigger rings around, the rings of space will be the zone of inhibition, showing how effective the antibiotic wouldve been. the bigger the zone of inhibition the better the antibiotic is.

4 stages involved:

1. discovery-discover the medicine
2. development-lab testing, devloping on cell tissue in labs
3. pre clinical trials-tests on cellsin dishes, animals
4. clinical trials-groups of humans, larger group, tens, hundereds, thousands.

stages and reasoning:

• the preclinical stage of testing is done on cells or tissues in the lab to find out whether the medicine gets into diseased cells and has the desired effect.
• testing may be carried out on animals to find out how the medicine affects body systems, without risking human health
• a small clinical trial is carried out on a few healthy people to find out whether the medicine is safe for humans to take and harmful side effects are limited. 
• a large clinical trial is carried out on many poeple with the disease to find out the right amount of medicine(dose) to use, and whetyher differnt people have differnt side effects. 

method: 

1. set up the tape measure to set up the transect line
2. take measuremmts at regular intervals along the transect
3. place top left hand corner at the measuremnt point on the transect line, measure the environmental factors(light intensity) and then count up the number of organisms of each kind in each quadrat
4. repeat step 3 as many times accross the transect line and record all results.

results:

check correlation bettween an environmental factor and the number of organisms recorded.