AP Biology Cell Size

Estimating Cell Size

Dual Enrollment Biology
Dual Enrollment Anatomy & Physiology

​Learning to Estimate Length

When doing microscopy, estimates of length are helpful but not precise. To start, you need to remember that the diameter of the circle of light you see will be considered "100%." The actual length of the diameter (called FOV for Field of View) changes with Total Magnification.

Look at the higher of the two cells (gray shapes with dark nuclei "dots" in the center). How long do you think that cell body is (from top to bottom)?

​

​Nerve cell body 100x

Open Ended

What proportion of the view-circle's diameter do you think the cell-body length takes up?

(Estimate a percentage, then move the decimal two places left to get proportion.)

Open Ended

Try again with the help of a grid:

What proportion of the view-circle's diameter do you think the cell-body length takes up now?

(The view diameter is 26 boxes long.)

​<-- use this FOV on the next slide

Open Ended

Now calculate the estimated cell length: $$Cell\ Length\ =\ cell\ proportion\ x\ FOV$$

Your answer should be in milimeters.

​Building your Search Image

When doing microscopy, it is often helpful to have a "search image" in your mind so that you know whether or not an object you find under the microscope is actually the subject of your search. The next slide shows a video clip of a cheek cell cluster that has been stained with Methylene Blue. Total magnification is 400x. While you watch the video, look for the cell membranes and the nuclei.

Multiple Choice

Which stain was used on the cheek cells?

• Methylene Blue

• Safranin

• TBD-O

• Gram's Iodine

Open Ended

What proportion of the Field of View (diameter) is taken up by the length of the cheek cell cluster (top to bottom)?

​<-- use this FOV on the next slide

Open Ended

Now calculate the estimated cell-cluster length: $$Length\ =\ proportion\ x\ FOV$$

Your answer should be in milimeters.

Multiple Choice

What is the dark dot in the center of each cheek cell?

• nucleus

• mitochondrion

• cytoplasm

• Golgi body

Multiple Choice

What is the dark line that circles the border of each cheek cell?

• nucleus

• mitochondrion

• cytoplasm

• cell membrane

Multiple Choice

What is the light lavender material that makes up most of each cheek cell?

• nucleus

• mitochondrion

• cytoplasm

• cell membrane

Poll

Are you ready to recognize cheek cells under the microscope?

• YES!

• Probably.

• Maybe?

• NO!

Poll

Are you ready to calculate cheek cell length under the microscope?

• YES!

• Probably.

• Maybe?

• NO!