Name : _____________________________________________Date: ____________Class: ___________
LAB: Onion Skin (Epidermal) Cells
Purpose: All living things are made-up of cells. Cells are the basic unit of structure and function of
living things. Cells are considered either prokaryotic or eukaryotic. Eukaryotic cells can be classified as
either plant-like (able to perform photosynthesis) or animal-like (not able to perform photosynthesis).
There are many types of plant-like and animal-like cells including muscle cells, brain cells, leaf cells, and
root cells. Though ALL cells have many things in common, plant-like and animal-like cells have certain
differences as well. In this lab we will observe the characteristics of plant cells.
Procedure:
1. Prepare a wet mount slide of onion skin, as previously shown by your teacher.
2. Use the microscope to observe the cells.
 Start with the 4X (smallest) objective lens.
 Then switch to the 10X (medium) lens.
3. Make a detailed drawing of ONE onion skin cell using the 10X (medium) objective lens.
Labels




Cell Wall
Cell Membrane
Cytoplasm
Nucleus
Ocular Lens Magnification: __________
Objective Lens Magnification: ________
Total Magnification: ____________
4. Label your drawing below with the names of the organelles from the box above.
5. Use the Grid Slide to measure the diameter of the field of view to the nearest 0.1 mm at this
magnification.
6. Use your drawing to estimate the number of onion skin cells that could fit across the diameter of the
field of view at this magnification. Estimate to the nearest 0.5 cells.
7. Calculate the average size of an onion skin cell. Show your work in the box below. Record your
answer to the nearest 0.01 mm/cell.
Average cell size = diameter of field of view (mm)
# of cells across the field of view
Show your work!
Final Answer: ___________________ mm/cell
8. Place the onion skin slide back on the microscope. Observe the slide using the 40X (largest)
objective lens. (Remember to start with the smallest lens, and then work your way up to the largest
lens.)
9. Make a detailed drawing of ONE onion skin cell using the 40X (largest) objective lens.
10. Label your drawing below with the names of the organelles from the box below.
Labels




Ocular Lens Magnification: __________
Cell Wall
Cell Membrane
Cytoplasm
Nucleus
Objective Lens Magnification: ________
Total Magnification: ____________
Questions: Read the article, “Why Don’t Onion Cells Have Chloroplasts?” to help you fill in
the blanks below.
https://www.reference.com/science/don-t-onion-cells-chloroplasts-b913e7219b44d618
Onion cells lack chloroplasts because the onion is part of the plant that is _____ involved in photosynthesis.
The part of the [onion] plant eaten by humans is called the ______________, and it resides at the base of
the plant.
Growing near the ground, the bulb is in poor position to collect ______________.
Photosynthesis is the process by which plants use sunlight, water, carbon dioxide and a [green] chemical
called ___________________, to create sugars.
Chloroplasts are small [green] organelles, located in ______________ plant cells, that contain [green]
chlorophyll and enable photosynthesis.
The onion is a photosynthetic plant, and it holds numerous chloroplasts [but only] in the _________, which
receive much more sunlight, but very few in other parts of the plant.