Zones of inhibition: measure radius and control the comparison
הוצג| English | משמעות |
|---|---|
| inhibition zone/ɪnhɪˈbɪʃn zəʊn/ | אזור דיכוי |
| control disc/kənˈtrəʊl dɪsk/ | דיסק ביקורת |
What would explain this observation?
- A clear circle around a treated disc indicates inhibited growth in that plate. Comparing circle diameters is useful only if the culture and treatment conditions are matched.
Build the model
- An inhibition zone 抑菌圈 is an area where growth has been prevented or reduced around an applied substance.
- Its size can reflect the effect on the approved bacterium, but also diffusion through the agar and the dose used.
- Required practical 2 compares antiseptics or antibiotics using agar plates and measurements of these zones.
- inhibition zone: An area of reduced or absent growth around a treatment in a culture.
- control disc 对照纸片: A comparison disc without the tested active treatment.
Which value belongs in πr² for a zone of diameter 20 mm?
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
The formula uses the RADIUS: for a 20 mm diameter, r = 10 mm, and area = pi x 10^2. Putting the diameter into pi r^2 quadruples the answer.
Match each technical term to its precise meaning.
רמת קושי 2/5 · 140 מטבעות + בונוס קטן בהשלמה הראשונה היום
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- For a circular region, area = πr².
- Radius is half the diameter.
- State whether the reported area includes the disc or subtracts its area: use the same convention for every treatment.
- A bigger zone does not on its own prove that the substance will treat a particular infection in a person.
In the lab: Under the school’s supervised microbiological protocol, use equal discs and applied amounts, the same approved organism and agar, matched incubation and a suitable control disc. Keep culture plates closed after incubation. Record repeated diameters through the centre if a zone is not perfectly circular, and explain the approximation.
Which two habits make the investigation or model in this case more defensible?
רמת קושי 2/5 · 140 מטבעות + בונוס קטן בהשלמה הראשונה היום
Stating the conditions and assumptions lets others repeat the work exactly, and recording the supporting evidence lets them check the conclusion. Hiding disagreeing results removes the evidence that could challenge a wrong conclusion, and one measurement can never establish a wider claim.
Work from known quantities
- Known: a zone diameter is 16 mm, giving radius 8 mm.
- Total circular area = π×8² = 64π, approximately 201 mm².
- If the disc diameter is 6 mm, its area is 9π, and the clear annulus is 55π, approximately 173 mm².
- The answer depends on the stated area convention.
Your turn: A circular zone has radius 5 mm. Using π=3.14, calculate total area.
A circular zone has radius 5 mm. Using π=3.14, calculate total area.
רמת קושי 2/5 · 140 מטבעות + בונוס קטן בהשלמה הראשונה היום
The result is 78.5 mm². Known: radius 5 mm; pi = 3.14. Use area = pi r^2. Area = 3.14 x 5^2 = 3.14 x 25 = 78.5 square millimetres. State whether the disc itself is included before comparing zone sizes.
Check the conclusion and its limits
- Do not put the diameter directly into πr².
- Matched incubation and a control are necessary for interpreting inhibition, and changing both substance and concentration prevents attributing the difference to one variable.
Not true: A larger inhibition zone automatically proves a treatment is suitable for every human infection. A zone shows the substance slowed growth under these conditions on this plate. Human treatment needs clinical evidence, dosing and safety trials - a bigger clear zone is not a prescription.
- An inhibition zone is an area where growth has been prevented or reduced around an applied substance.
- For a circular region, area = πr².
- Watch for: do not put the diameter directly into πr².
A zone shows the substance slowed growth under these conditions on this plate.
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
True. A zone shows the substance slowed growth under these conditions on this plate. Human treatment needs clinical evidence, dosing and safety trials - a bigger clear zone is not a prescription.
An area of reduced or absent growth around a treatment in a culture: write the technical term.
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
inhibition zone means An area of reduced or absent growth around a treatment in a culture.