2.1
Ocular Micrometer
Introduction
An ocular micrometer is a glass disc with the ruled
scale which can fit in eyepiece of microscope. It is used to measure the exact
size of an object. It must be calibrated with a stage micrometer to determine
the precise distance between the lines of ocular micrometer. The correct method
to use the ocular and stage micrometer is rotate one of the microscope eyepiece
until the lines of the ocular micrometer are parallel with the lines of stage
micrometer. Then, the position of stage micrometer is adjusted until the
graduations of the ocular micrometer are superimposed over those of the stage
micrometer. The exact distance of each ocular division can be counted by
determining the number of ocular micrometer spaces that fall within a given
number of stage micrometer spaces. The stage micrometer will be then replaced
by the slide with specimen to measure the length and width of that cell.
Objective
To measure the dimensions of cell using microscope
To learn the correct method of using ocular
micrometer and stage micrometer
Materials
and reagents
Microscope fitted with an ocular micrometer, slide
micrometer, stained preparations of yeast
Procedure
(Refer to lab manual)
Results
The dimension of the yeast
For 10 x objective lens, 1mm is equal to 9.6 ocular
divisions
For 40 x objective lens, 0.1mm is equal to 8.0
ocular divisions
The length of the yeast:
8 ocular unit= 0.1mm
0.4 ocular unit= 0.005mm
=5.0µm
The width of the yeast:
8 ocular units= 0.1mm
0.5ocular unit= 0.0063mm
=6.3µm
Discussion
In order to measure the size of the cell, the ocular
micrometer must be calibrated with stage micrometer to get the correct scale to
measure the microorganisms. This is due to the appearance of image in ocular
micrometre will not change with the change of magnification but scale on stage
micrometre will change with the change in of magnification. In this experiment,
parallax errors should be prevented when calibrate the ocular micrometre with
the stage micrometer and also each time when measuring the size of the cell.
Conclusion
Through this experiment, we know the importance of
using the ocular micrometre in determining the specific size of the cell and
the correct method to use it together with stage micrometer. The length of
yeast is 0.005mm and the width of yeast is 0.0063mm.
Reference
https://en.wikipedia.org/wiki/Ocular_micrometer
2.2
Neubauer Chamber
Introduction
The Neubauer chamber (hemocytometer) is a thick
crystal slide with the size of a glass slide (30mm x 70mm x 4mm thickness). It
is used to count cells and to determine the concentration of cells. The chamber
has three parts (central part, upper chamber and lower chamber). At the central
part, there is a counting grid on the glass. The upper chamber and lower
chamber are the counting areas. There is a special glass cover placed on the
top of the Neubabuer chamber which will cover the central area.
Materials
and Reagents
Dilutions of yeast cultures, neubauer and
coverslip, sterile Pasteur pipettes
Procedure
(Refer to lab manual)
Results
|
10
|
|
|
28
|
|
|
40
|
26
|
|
|
|
|
11
|
|
|
19
|
23
|
|
24
|
Total cells in the random 8 boxes
= 10+19+40+23+26+11+28+24
=181cells
Average number of yeast cells per boxes
=181/ 8
=22.625 cells per boxes
Volume of one box
=0.25mm x 0.25mm x 0.1mm
=6.25 x 10-3mm3
=6.25 x 10-6 ml
After dilution
=6.25 x 10-7 ml
Concentration of cells
=22.625/ (6.25 x 10-7ml)
=36200000cells/ml
=3.62 x 107 cells/ml
Discussion
The middle large square has the length of 1mm, width
of 1mm and depth of 0.1 mm. Inside the large square there was 16 smaller
squares, each with the size of 0.25mm x 0.25mm. About 8 of the smaller square were
taken randomly and the cells were counted in each of those smaller squares. The
average number of the yeast is 22.625 cells per box. By using the formula of
cells concentration, the concentration of the cells is 3.62 x 107 cells/ml.
Conclusion
Naubauer Chamber is a special slide made to count
the cell in drop of specimen and in estimating the concentration of cell in
unit of cell/ml. In this experiment, the concentration of the cell is 3.62 x 107cells/ml.
Reference
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