Principles and Methods Lab: Exploring Cells
Prelab:
1. What is the major difference between a prokaryotic and eukaryotic cell? What
types of organisms are found in each?
2. List three differences between a typical plant cell and a typical animal cell.
3. What do the following parts of a microscope do?
Eyepiece
Objective lenses
Condenser
Diaphragm
Course adjust knob
Fine adjust knob
Stage adjust knob
Introduction:
In this lab, we will use a compound microscope to study cells. Familiarize
yourself with the parts shown in the diagram below and their functions before
proceeding:
When using a microscope, it is important to report the total magnification of any
images seen. To do this, you must multiply the magnification of the eyepiece lens
(10x for these microscopes) by the power of the objective lenses. They are listed
below:
Scanning lens = 4x
Low Power = 10x
High Power = 40x
Oil Immersion = 100x
We will examine a total of seven slides. They are:
Zea root tip
Alium epidermis
Generalized animal cell
Neuron
Paramecium
Stentor
Cheek cell smear
Instructions for making a cheek cell smear:
1) Obtain a clean blank slide and a slip cover.
2) Using a toothpick, gently rub the insides of the cheeks. Then rub the toothpick
on the blank slide.
3) Add one drop of methylene blue. This will stain cell structures especially the
nucleus.
4) Place cover slip on top. Use tissue paper to wick away any excess stain.
5) Observe the slide. Note the cells and their structures. Also, look for the presence
of bacteria (small dark specks).
FOR THE DATA SECTION OF THE REPORT:
- Add drawings for each of the seven slides. For each drawing, label any cell
structures seen and write the total magnification used to view the slide.
- Show the calculations for total magnification for each objective lens
(scanning, low, high, oil).
FOR THE OBSERVATIONS SECTION:
- Add written observations for which structures are present and what kinds
of differences/similarities exist between the slides.
Questions:
1. Place each of the slides into one of the following categories: Plant, animal, or
protist. What do all of these cell types have in common?
2. What differences did you see between the plant cells and the animal cells?
3. How is the neuron different from the generalized animal cell? How might this
relate to the neuron's function?
4. When you increase magnification, does your field of view get bigger or smaller?
Why is it important to center your subject before switching to higher magnification?