AQA GCSE Biology Microbiology Flashcards
(16 cards)
State two aseptic techniques that should be used
. Disinfect hands
. Work near a flame
Explain why students work at 25.C not 37.C
. Harmful pathogens are more likely to grow above 25.C
. Cultures incubated at higher temperatures grow a lot faster so students can’t study them
Why must you soak the paper discs in sterile water and not in an antibiotic?
. Sterile water prevents any unwanted bacteria from getting onto the disc
. Sterile water prevents the antibiotic from being diluted
Why do you need to use a paper disc that has not been soaked in an antibiotic?
To act as a control
Why must Petri dishes and culture medium and inoculating loop be sterilised before use?
To kill any unwanted bacteria that might be lurking on them
After transferring the bacteria, why must the lid of the Petri dish be lightly tapped on?
To stop microorganisms from the air getting in
Why should the Petri dish be stored upside down?
To stop drops of condensation falling onto the agar surface.
Why must you leave space between the discs?
So bacteria from one disc doesn’t spread onto another
What is the independent variable in this practical?
The type of antibiotic you apply to the discs
What is the dependent variable in this practical?
The size of the zone of inhibition
State two control variables in this practical
. Temperature
. Size of paper discs
State one hazard and safety precaution for this experiment
. Bacteria could be passed onto someone
. Sterilize equipment before use
State two ways this experiment can be improved.
. Controlling the incubation temperature
. Sterilising equipment
The larger the inhibition zone…
The more effective the antibiotic is
Why can’t viruses be grown on agar?
Because they are not living organisms and need a host cell to reproduce
What is the purpose of this investigation?
To investigate the effect of antibiotics on bacterial growth
