Biology 2070H - Lab #1 MICROSCOPY AND CHARACTERIZATION OF CELLS
Introduction: Cells can be very difficult entities to study. They are usually very small and transparent, yet extremely complex. Fortunately, there are many tools available to the cell biologist that aid in their study. The light microscope is to this day perhaps the single most important instrument used in Cell Biology. It is used under bright field conditions to study the organization of cells in fixed and stained sections of tissues. With phase contrast optics it is possible to monitor the movements of living cells and to observe changes in their subcellular organization. The light microscope may also be used to monitor certain operations such as cell fractionation and biochemical characterization of cellular components. See the following pages in ECB3 for more useful information: Microscopy: p. 6 -11 Characteristics of cell types: much of Chapter 1, see especially Panel 1-2 Cell Cultures: p. 157 and 161
Since cells are so difficult to examine without the aid of a microscope, they are not things that we are used to seeing everyday. In this exercise we will 1) review how to use a compound microscope 2) examine and compare different types of cells (eg. plant, animal, fungus, eukaryotic, prokaryotic) 3) gain an appreciation of the relative sizes of different types of cells 4) review how to estimate field size and the size of a cell under the microscope. 5) learn about different types of light microscopes and how they are used It is helpful to work with a partner, so that you can discuss what you’re observing.
I. COMPOUND MICROSCOPES Review the section on how to use a compound microscope at the beginning of this manual. You should go through this section on your own and consult with the course TAs if you have any questions. If you have not previously learned how to use a compound microscope, please consult with your TA.
TYPES OF CELLS AND THEIR RELATIVE SIZES
The objective of this part of the lab is to examine a variety of types of cells in order to discover some of their general characteristics. Examine the cells that are available to you (these may deviate somewhat from the following list, depending on availability). Then answer the questions that are at the end of the lab.
USE STERILE TECHNIQUE AS DEMONSTRATED BY YOUR T.A. WHEN HANDLING ALL FRESH MATERIALS Material that will be available for you to examine will include the following: A. B. C. D. E. F. G. 0.85% NaCl suspension washed red blood cells Suspension of yeast Suspension of bacteria Suspension of algae You will prepare a smear of your own cheek cells. Cultured animal cells (cells growing in vitro) There will be several prepared and stained slides for you to examine, to help you in understanding your observations for A to E.
Procedure: A to D Suspensions: 1. For A to D above, place a loopful of one of the suspensions on a glass slide. Cover with a cover-slip avoiding excessive air bubbles. If excess fluid escapes from the cover-slip, it may be removed by blotting with the end of a paper towel strip which is then discarded in a disinfectant jar. Examine each wet mount successively under low (10), high dry (40), and oil immersion (100) objectives. You will be given a demonstration of how to use oil immersion. Please follow the instructions very carefully, in order not to damage the microscope objectives. In your lab notebook, describe or illustrate your observations at the most informative magnification. Be creative in your observations. Note the colour of each cell type, its movements, any internal features, anything that makes it distinct from the other cells. Also note any similarities. How do eukaryotic cells differ from prokaryotic cells? How do plant cells differ from animal cells? For A to D, estimate the size of each type of cell, using the method described at the beginning of the lab manual. If the bacterial cells are too difficult to observe, try preparing...