Biology Topic Practice

Calculating Zones of Inhibition

To compare antibiotics, we measure the area of the "clear zone" around an antibiotic disc on an agar plate.

Which mathematical formula do we use to find the area of the zone?

What is Calculating Zones of Inhibition?

"The zone of inhibition is a circular area around an antibiotic disc where bacterial growth is suppressed."

Question 1

In a zones of inhibition investigation, what does a larger clear zone around a disc usually show?

Question 2

To calculate the area of a circular zone of inhibition, which measurement is needed first?

Question 3

If a zone of inhibition has a diameter of 10 mm, what is its radius?

Measuring Effectiveness

The clear zone where bacteria haven't grown is called the zone of inhibition.

Measure the diameter of the zone with a ruler.

Calculate area using Area = πr².

Exam Tip

A larger zone of inhibition means the antibiotic is more effective at killing that specific bacteria.

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