LAB 2: MEASUREMENT AND COUNTING OF CELLS USING MICROSCOPE
2.1 Ocular Micrometer
Introduction
Ocular micrometer is use in order to measure and compare the size of prokaryotic and eukaryotic microorganism. Microorganisms are measured with an ocular micrometer which is inserted into the one of the microscope eyepieces. The micrometer, which serves as a scale or rule, is a flat circle of glass upon which are etched equally spaced divisions. This is not calibrated, and may be used at several magnifications. When placed in the eyepieces, the line superimposed certain distance markers on the microscope field. The actual distance superimposed may be calibrated using a stage micrometer on which parallel lines exactly 10 µm apart etched. By determining how many units of the ocular micrometer superimpose a known distance on the stage micrometer, you can calculate the exact distance each ocular each ocular division measures on the microscopic field. When you change objectives you must recalibrate the system. After calibration of ocular micrometer, the stage micrometer is replaced with a slide containing microorganism. The dimensions of the cells may then be determined.
Objective
To measure and count cells using microscope
Results
1) Lactobacillus
40 x magnifications
100 x magnifications
2) Yeast
40 x magnifications
100 x magnifications
Discussion
In this experiment, we are using ocular micrometer to measure and compare the size of prokaryotic and eukaryotic microorganisms. By using the lowest power of objective lens, we focus the microscope until the image of the stage of micrometer is observed superimposed on the eyepiece scale and then we calibrate it.
Eukaryotes are the most complex organism and it can be single cell or multicellular cell while prokaryotes are only in single cell. Normally, prokaryote has a regular in shaped compared to eukaryote because prokaryotes are lack in some such organelles for examples a chloroplast, endoplasmic reticulum, nucleus and a cell membrane.
During this experiment, yeast is also used as the examples of eukaryotic organism and prokaryotic organism we used is lactobacillus. Both organism has been observed by using 400x magnifications and 1000x magnifications under the microscope due to the tiny structure of both organisms.
400x magnification
|
1000x magnification
| |||
calibrate
|
Stage micrometer
|
Ocular division
|
Stage micrometer
|
Ocular divison
|
0.03 mm
|
38 division
|
0.09 mm
|
96 division
| |
7.9x10⁻⁴ mm
|
1 division
|
9.38x10⁻⁴ mm
|
1 division
| |
0.79 µm
|
1 division
|
0.94 µm
|
1 division
| |
Size of microorganism : 2 division 5 division
YEAST:
4 division
x 0.94 µm
= 6.58 µm
LACTOBACILLUS:
400x magnification
2 division x 0.79 µm
=1.58 µm
1000x magnification
5 division x 0.94 µm
=4.7 µm
Conclusion
As the conclusion, we are able to learn more on measuring and counting the cells by using a microscope. An ocular micrometer is a glass disks that are attaches to a microscope’s eyepiece. An ocular micrometer has a ruler; that are calibrated with a slide of micrometer that are allows the user to measure the size of magnified of the objects. The distance between the marks on the ruler are depends upon the degree of magnification. We used this ocular micrometer to observe prokaryotic and eukaryotic cells since these two cells are very small and tiny organisms.
Reference
http://www.ehow.com/how_5019336_use-ocular-micrometer.html
Pearson International edition Biology 8th Edition, Campbell. Reece
2.2 Neubauer Chamber
Introduction
Neubauer chambers are more convenient for counting microbes. The Neubauer is a heavy glass slide with two counting areas separated by a H-shaped trough (see figure 2.1). A special coverslip is placed over the counting areas and sits a precise distance above them.
Objective
To counts the cells using microscopes.
Result
Yeast 400x magnification
Discussion
In the second experiment, we used neubauer chamber because it more convenient to count the microbes. During this experiment there are some steps of sterilizations that we used to do it. If in the open work space, the flame of sterilizations is used to eliminate the potential contaminants from the expose of the openings of the bottle containing yeast during the transfer process. We also sterilized Pasteur pipette. As this sterilization technique is used to ensure us from being infected from the microorganism and also prevent from the microorganism to spread.
Last but not least, we need to do a little bit in a calculation. The chambers are contain nine majors large square, so for the calculation we only used the middle large square. Inside the middle large square, there are sixteen smaller squared. Then we randomly choose ten out of sixteen smaller square and then we calculate the number of cells in each of the square.
56 ÷ 10 = 5.6
= 6
Volume = 0.05 x 0.05 x 0.01 mm
= 2.5 x 10⁻⁵ mm
= 2.5 x 10⁻⁷ ml
6 cells in 16 squares
1 square = 6 ÷16
= 0.375 cells in 2.5 x 10⁻⁷ ml
1ml = 0.375 ÷ 2.5 x 10⁻⁷
= 1500000 cells / ml
Conclusion
As the conclusion, we can use both methods to measure and counted the cells using some methods. The first method is using ocular micrometer and the second is by using Neubauer chambers. By using Neubauer chambers, we can get more convenient in counting the cells compared to the ocular micrometer. This is because, when using Neubauer chambers, the sterilization is needed to avoid any contaminant. Hence, Neubauer chambers are most suitable to count the cells in microorganisms.
Reference
1. Pearson International Edition Biology, 8th Edition, Campbell, Reece
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