5.16-5.22 Treating Disease Flashcards
(12 cards)
Explain why antibiotics can only be used to treat antibacterial infections.
Because they inhibit cell processes in the bacterium but not the host organism.
The bacteria is killed by antibiotics.
Other pathogens use cell machinery in host cells to reproduce.
Explain the use of an autoclave to prepare sterile growth medium and petri dishes
Otherwise, they may be contaminated with other microorganisms. These could be harmless but will compete with the desired bacteria for nutrients and space, or be harmful, potentially producing a new pathogen.
Explain the use of sterile inoculating loops to transfer microorganisms
This kills unwanted microorganisms.
These could be harmless but will compete with the desired bacteria for nutrients and space, or be harmful, potentially producing a new pathogen.
Explain the need to keep petri dishes and culture vials covered.
Sealing stops airborne microorganisms from contaminating the culture, but it should not be sealed all the way around as this would result in harmful anaerobic bacteria growing (due to no oxygen entering).
Describe the aseptic technique (and why it’s used) for the core practical investigating the effects of antibiotics
-Glass Petri dishes and agar gel must be sterilised in an autoclave before use or pre-sterilised plastic Petri dishes can be bought.
Reason – this will kill any bacteria that are present in the solution or on the Petri dishes.
-Pour the sterile agar plates and allow to fully set.
Reason – this provides the selected bacterium with all the nutrients needed to grow.
-Unwrap a sterile spreader or sterilise a spreader in ethanol. Use the spreader to spread the microorganism solution across the entire surface of the agar plate.
Reason – this allows a lawn of bacteria to be produced across the whole of the plate. Replace the lid as soon as possible, secure with tape.
-Label and invert the plate, and store upside down.
Reason – this stops additional unwanted bacteria in the air contaminating the plate. Do not fully seal the lid, as this will stop oxygen reaching the bacterium, and this may encourage harmful anaerobic bacteria to grow. Labels are important, as this identifies the growing bacterium.
-Incubate at a maximum temperature of 25°C in schools and colleges.
Reason – this reduces the chance of growing harmful pathogens.
Describe the core practical for investigating the effects of antibiotics.
-Soak filter paper disks in a variety of solutions, use either different concentrations of the same solution, or a variety of different solutions.
Reason - the effectiveness of the solutions at killing the bacteria can be tested.
-Split a petri dish into four sections on the base using opaque tape, label each based on the antibiotics, except one which is a control. Place the corresponding antibiotic in each section and white paper discs in the control.
-Leave for multiple days
-Measure the clear area around the soaked filter paper disks. A control disk must be also included. Use a ruler and the equation π r²
Reason - size of zone indicates the effect of the substance tested on the growth of the specific bacterium.
Describe the process of developing new medicines.
-Discovery: in plants or microorganisms or synthesised by chemists.
-Development
-Preclinical testing using cells, tissues and live animals
-Clinical testing first on healthy volunteers with a low dose. Then split patients with one group receiving a drug and the other group a placebo so the effect of the drug can be observed.
This then needs to be peer reviewed to check for repeatability.
(Testing needs to check toxicity, efficacy, and dose)
Describe the production of monoclonal antibodies
-Scientists obtain mice lymphocytes (a type of white blood cell that make antibodies but cannot divide), which have been stimulated to produce a specific antibody.
-They are combined with tumour cells (do not make antibodies but divide rapidly) to form a cell called a hybridoma.
-The hybridoma can divide to produce clones of itself, which all produce the same antibody
-The antibodies are collected and purified.
Explain the use of monoclonal antibodies in pregnancy tests
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.
The antibodies are attached to blue beads. The antibodies are also present in the result window where antibodies carrying hCG can bind and stay.
Some antibodies with no hCG will move past this to the control window.
Explain the use of monoclonal antibodies in locating the position of blood clots/cancer cells
-The monoclonal antibodies are modified so that they will bind to the molecule you are looking for (such as antigens on a blood clot/cancerous cells).
-The antibodies are also bound to a fluorescent dye
-If the molecules are in the sample then the antibodies can bind to it, and the dye can be observed
Explain the use of monoclonal antibodies in the treatment of disease, e.g. cancer
*Cancer cells have antigens on their cell membrane called tumour markers which can be targeted.
Three ways to treat cancer with monoclonal antibodies:
-Producing monoclonal antibodies that bind to the tumour markers in order to stimulate the immune system to attack the cells.
-Using monoclonal antibodies to bind to receptor sites on the cell surface membrane of the cancer cells. This means growth-stimulating molecules cannot bind, stopping the cell from dividing.
-Using monoclonal antibodies to transport toxic drugs, chemicals or radioactive substances as they can only bind to cancer cells.
Explain the advantages of using monoclonal antibodies to target specific cells compared to drug and
radiotherapy treatments
-They only bind to specific cells, meaning healthy cells are not affected.
-They can be engineered to treat many different conditions.
-We are now able to produce mouse-human hybrid cells to reduce the chance of triggering an immune response.
