Video Transcript
The micrograph provided is of a
nucleolus in a cell. Which type of microscope is most
likely to have been used to produce this image? (A) Transmission electron
microscope, (B) scanning electron microscope, (C) light microscope.
To figure out which microscope made
this image, we must first understand the scale of what we are looking at.
A nucleolus is a structure within
the nucleus of a eukaryotic cell. The nucleolus in this image is
likely only a few microns across. A micron is one millionth of a
meter. Humans can’t see much smaller than
one ten thousandth of a meter, or 0.1 millimeters. This means the nucleolus is not
visible by the unaided human eye. So, the type of microscope that
would produce this image must be capable of magnifying objects one million times
their actual size.
The answer provides us with three
options: a light microscope and two different types of electron microscopes, the
scanning electron microscope, or SEM, and the transmission electron microscope, or
TEM. Let’s review the properties of
these microscopes to identify the correct answer choice.
Light microscopes produce 2D color
images that can differentiate between different cells in a tissue or between basic
large organelles in a cell. This is because they use light,
which has a large wavelength and therefore a low resolution. So, it can only magnify objects up
to 1500 times their actual size.
Scanning electron microscopes, or
SEMs, produce 3D black-and-white images of the exterior surface of a cell or
specimen, such as viruses, bacteria, or pollen grains. SEMs use electrons to magnify
objects up to two million times their actual size.
Transmission electron microscopes,
or TEMs, produce 2D black-and-white images of a cell’s ultrastructures and cellular
organelles. TEMs use electrons to magnify
objects more than 50 million times their actual size.
Now that we have reviewed the
property of these three types of microscopes, we can reevaluate the answers. Light microscopes have limited
resolution. So, we can eliminate this as a
possible answer. Although scanning electron
microscopes have enough magnifying power to produce the image of the nucleolus, they
produce detailed, 3D images of the surface of specimens. The nucleolus is found in the
interior of the nucleus of a specimen. So, this answer choice is also
incorrect. Transmission electron microscopes
produce 2D black-and-white images of the cell’s ultrastructure and organelles like
the nucleolus. So, this is most likely our
answer.
With this information, we can now
identify the correct answer. The type of microscope that is most
likely to have been used to produce the image of the nucleolus is a transmission
electron microscope.
