Matric No. : 111356
Lab 2:Measurement and counting of cells using microscope
2.1 Ocular Micrometer
Introdution:
Ocular micrometer is use in order to measure and compare the size of prokaryotic and eukaryotic microorganisms.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 uponwhich are etched equally spaced divisions.This is not calibrated,and may be used at several magnifications.When placedin the eyepiece,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 10µm apart etched.By determining how many units of the ocular micrometer superimposed a known distance on the stage micrometer,you can calculate the exact distance each ocular division measures on the microscopic field.When you change objectives you must recalibrated the system.After calibration of the ocular micrometer,the stage micrometer is replaced with a slide containing microorganisms.The dimension of the cells may then be determined.
Objective:
To measure the size of the cells using a microscope
Result:
|
10 divisions stage superimpose with 40 divisions of ocular
micrometer
10 divisions on stage scale = 10 x 0.01mm
= 0.1mm
10 divisions on stage scale coincide with 40 divisions on ocular
micrometer
So, one ocular division = 0.1mm / 40
= 0.0025mm/2.5μm
1 division of stage scale superimpose with 10 divisions of
ocular micrometer
1
division on stage scale =1 x 0.01mm
= 0.01mm
1
divisions on stage scale coincide with 10 divisions on ocular micrometer
So,
one ocular division = 0.01mm / 10
= 0.001mm/1μm
The Lactobacillus cell is in 2 divisions, so the
dimension is calculated
0.001mm x 2 = 0.002mm
=
2μm
There is total 3 division of the
yeast cell, so the the calculation will be
0.001mm x 14 = 0.014mm
= 14μm
Discussion:
1)
An ocular
micrometer is a glass disk that fits in a microscope eyepiece that has a ruled scale, which is used to measure the
size of magnified objects.
2)
Through the ocular micrometer,we can estimate the size
of the Lactobacillus is 2 micrometer and
the size of yeast is 14 micrometer
.
3) Scientist
prove that the size of Lactobacillus
is only 2 to 10 micrometers, which is
approximately the size of a red blood cell.
4) Scientist prove that yeast
size can vary greatly depending on the species, typically measuring 3–4 µm
in diameter,
Conclusion:
By using
ocular micrometer,we can measure the size of the Lactobacillus and yeast.The
size of Lactobacillus is 2 micrometer and the size of
yeast is 14 micrometer .
References:
en.wikipedia.org/wiki/Yeast
2.2 Neubaucer
Chamber
Introduction:
Neubaucer
chamber are more convenient for counting microbes.The Neubaucer is a heavy
glass slide with two counting areas separated by a H-shaped trough.A special
coverslip is placed over the counting areas and the sits a precise distance
above them.
Objetive:
To count the cell by using microscope
Result:
Average number of the cells per square
box
34+39+36+34+43+44+40+43+33+37 =38.3
10
Volume of the square:
0.2mm X 0.2mm X 0.1mm =0.004mm³
0.004mm³ / 1000 =0.000004cm³
38.3 cells in 0.000004mL, thus
Concentration of the cells
= 38.3 cells / 0.000004 mL
=
9575000 cells/mL
Cell as observed on a Neubaur chamber
Discussion:
1) Hemocytometer used for determining the number of cells per
unit volume of a suspension .
2) The
ruled area of the hemocytometer consists of several, large, 1 x 1 mm
(1 mm2) squares. These are subdivided in 3 ways; 0.25 x
0.25 mm (0.0625 mm2), 0.25 x 0.20 mm (0.05 mm2)
and 0.20 x 0.20 mm (0.04 mm2). The central, 0.20 x
0.20 mm marked, 1 x 1 mm square is further subdivided into 0.05 x
0.05 mm (0.0025 mm2) squares. The raised edges of the
hemocytometer hold the coverslip 0.1 mm off the marked grid. This gives
each square a defined volume.
3) The
cell-sized structures counted lie between the middle of the three lines on the
top and right of the square and the inner of the three lines on the bottom and
left of the square.
Conclusion:
By using Neubaucer chamber,we are able to determine
the concentration of the yeast in the sample.
References:
|
No comments:
Post a Comment