Determination of the actual size of a component in an electron micrograph

The information provided on a micrograph to determine actual size could be either a size bar or the magnification of the micrograph. Note: Although this micrograph provides both, only one (size bar or magnification) is usually given.

Determining size of a component using a size bar.

Under the size bar is information as to the size it represents. Actual size of a component can be determined using the following equation:

size of component =

(measured size of the component in the micrograph) X (the size the size bar represents) / (the measured size of the size bar)

Determining size of a component using magnification of the micrograph.

Actual size of a component can be determined using the following equation:

size of component = (measured size of the component in the micrograph) / (magnification of the micrograph)

Determine the width of the cell membrane from the transmission electron micrograph provided.

Width of membrane = 7-8 nm = 0.0000077 mm (based on a measurement of 2 mm in the micrograph)

Given your answer, what can you conclude about the ability to observe the cell membrane using the compound microscope.

Given that the limit of resolution (the minimum distance which must separate two points for them to be distinguished as two distinct points) is approximately 0.5 micrometers for the compound microscopes used in this lab, it would be impossible to observe the cell membrane with the compound scope.

Determine the sizes of the animal cell, the plant cell and the chloroplast in the electron micrographs provided.

The following sizes are ranges only. Actual cell size may be larger or smaller and will depend largely on cell type.
Size of animal cell = 10 - 30 micrometers
Size of plant cell = 10 - 100 micrometers
Size of chloroplast = approximately 5 micrometers

Does this agree with your previous estimations of size using the compound microscope?

The agreement with your previous estimations will depend on the different types of plant and animal cells measured.

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