IB Biology: A2.2-Measuring Cells

Front

What units are used to measure cells?

Back

Cells are measured in metres, but due to their small sizes, they are measured in additional units in multiples of a thousand smaller or larger, using standard prefixes.

Front

What instruments are used to measure cells?

Back

The eyepiece graticule and stage micrometer

Front

What is an eyepiece graticule?

Back

A transparent scale placed in the eyepiece of the microscope to measure the length of a cell in eyepiece units.

Front

How many divisions does an eyepiece graticule typically have?

Back

It typically has 100 divisions.

Front

What is the purpose of calibrating the eyepiece graticule?

Back

To determine the actual length of eyepiece units using a stage micrometer.

Front

What is a stage micrometer?

Back

A miniature transparent ruler found on a special glass slide used to calibrate eyepiece units.

Front

What are the subdivisions of a stage micrometer?

Back

It has subdivisions of 0.1mm and 0.01mm.

Front

How is the eyepiece graticule calibrated?

Back

By superimposing the images of both the eyepiece graticule and stage micrometer and counting the eyepiece units that correspond to 0.1mm.

Front

What is the process to measure a cell in eyepiece units?

Back

Calibrate the eyepiece units with a stage micrometer to determine the length of one eyepiece unit, then multiply the length of one eyepiece unit by the eyepiece measurement.

Front

How do you convert from mm to µm?

Back

Multiply the length in mm by 1000 to convert to µm.