CCEA A-Level Life and Health Sciences 0008
Experimental Techniques
Human Body Systems
Physical Chemistry in Industrial Processes
Brain ScienceDouble Award
Material ScienceDouble Award
Medicine, Drugs and Clinical TrialsDouble Award
Scientific Method, Investigation, Analysis and Evaluation
Organic Chemistry
Medical PhysicsA2 option
Sound and LightA2 option
Genetics, Stem Cell Research and CloningA2 option
MicrobiologyDouble Award
Oral Health and DentistryDouble Award
Histology and PathologyDouble Award
Analytical Chemistry TechniquesDouble Award
Enabling TechnologyDouble Award
Microbiology
Aseptic technique, growth media and inoculation
- 3 things to know
- A2 6
Overview
Aseptic technique and flaming loops, disinfection and sterilisation, preparing media and filter sterilisation, streak, pour and lawn plates, mycelial discs, plaque assays and safe incubation.
What you need to know
Answer each one before you reveal it.
How is an inoculating loop sterilised?
Why is work carried out close to a Bunsen burner flame?
Questions from this subtopic
Each one with the model answer underneath.
- 1
What is aseptic technique?
Model answer
Aseptic technique is the set of practices that prevent unwanted microorganisms contaminating a culture. The same practices also stop the culture escaping into the environment.
- 2
How is an inoculating loop sterilised?
Model answer
The loop is heated in a Bunsen flame until it glows red hot. The loop is cooled for a few seconds before it touches the culture, so the microorganisms are not killed.
- 3
Why is work carried out close to a Bunsen burner flame?
Model answer
The flame creates an updraught of hot air. Airborne microorganisms are carried away from the open culture.
- 4
What is the difference between disinfection and sterilisation?
Model answer
Disinfection reduces the number of microorganisms on a surface to a safe level. Sterilisation kills or removes all microorganisms, including spores.
- 5
How is a growth medium prepared and sterilised?
Model answer
Nutrient powder and agar are dissolved in water and heated. The medium is then autoclaved before being poured into sterile Petri dishes.
- 6
How is a heat-sensitive solution, such as an antibiotic, sterilised?
Model answer
The solution is passed through a membrane filter with pores about 0.2 µm across. Bacteria are trapped, and the filtered solution is sterile.
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