Lab 2 Report Prepared by Teoh Leong Sin
Name: Teoh Leong Sin
Matric No: 111433
2.1 Ocular Micrometer
Introduction
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 upon which are etched equally spaced
divisions. This is not calibrated, and may be used at several
magnifications. When placed in 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 10 micrometer 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
division measures on the microscopic field. When you change objectives
you must recalibrate the system. After calibration of the ocular
micrometer, the stage micrometer is replaced with a slide containing
microorganisms. The dimensions of the cells may then be determined.
Objective
To measure and count cells using a microscope.
Results
Total magnification = objective lens power x eyepiece lens power(10x)
Yeast under 400x magnification:
2.5 micrometer x 2 = 5 micrometer
Yeast under 1000x magnification:
1.0 micrometer x 5 = 5 micrometer
Lactobacillus under 1000x magnification:
1.0 micrometer x 2.5 = 2.5 micrometer
Discussions
1) The ocular micrometer is a glass disc that attaches to a micrometer's eyepiece.It has a ruler that allow user to measure the size of magnified object.
2) The actual size of the letter on the microscope slide is measured using the
millimeter ruler. This measurement will help us calibrate the ocular
micrometer to determine if it is giving us accurate measurements.
3)The
scale on the ocular micrometer changes with total magnification, and thus has
no absolute value.A stage micrometer is essentially a ruler that is
mounted on a microscope slide . One division of stage micrometer = 0.01 mm.
4) One ocular division = no. of divisions on stage micrometer
no. of divisions on ocular micrometer
5) For 400x magnification:
Stage scale = 0.01 mm x 5 divisions
= 0.05 mm
one ocular division = 0.05 mm/20 divisions on ocular micrometer
= 0.0025 mm
= 2.5 micrometer
measurement scale of sample yeast cells = 2.5 micrometer x 2 ocular divisions
= 5.0 micrometer
measurement scale of sample lactobacillus cells = 2.5 micrometer x 1 ocular division
= 2.5 micrometer
6) For 1000x magnification:
Stage scale = 0.01mm
one ocular division = 0.01 mm/10 divisions on ocular micrometer
= 0.001 mm
= 1.0 micrometer
measurement scale of sample yeast cells = 1.0 micrometer x 5 ocular divisions
= 5.0 micrometer
measurement scale of sample lactobacillus cells = 1.0micrometer x 3ocular division
= 2.5 micrometer
Conclusion
Ocular
micrometer allows us to measure the size of microorganisms . Microorganisms or cells such
as yeast and lactobacillus can be measured and the size can be
compared. The result show that yeast cells is two times bigger than lactobacillus cells.
t
References
http://www.doctorfungus.org/thelabor/sec11.pdf
http://www.ruf.rice.edu/~bioslabs/methods/microscopy/measuring.html
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. A special coverslip is placed over the counting areas and sits a
precise distance above them.
Objective
To measure and count cells using a microscope
Results
Yeast under 400x magnification:
11 |
8
|
15 |
6 |
12
|
20 |
9
|
|
14
|
|||
11
|
9
|
Discussions
1) Neubauer Chamber is device originally designed for the counting blood cells.It is now using to count other cells and microorganisms
2) The device is carefully crafted so that the area bounded by the lines
is known, and the depth of the chamber is also known. It is therefore
possible to count the number of cells or particles in a specific volume
of fluid, and thereby calculate the concentration of cells in the fluid
overall.
3) We randomly choose 10 of these 16 smaller squares and calculate the number of yeast cells in each of the squares,then we calculate the average of yeast cells to further determine the concentration by dividing the volume of a small square.
4) Volume of small square = 0.2mm x 0.2mm x 0.1 mm
= 0.004 mm^3
= 4 x 10^-6 mL
Sum of cells in 10 small box = 115 cells
Average cells = 115 cells/ 10
= 11.5
Concentration of yeast cell = 11.5 cells / (4 x 10^-6) mL
= 2875000 cells/mL
Conclusion
The
number of cells in a population can measured by counting the number of
cells in smaller squares and the volume of suspension is equal to area
of smaller square times depth of film.With using Neubauer chamber, we
can easily calculate the concentration of microorganisms or cells.The concentration of yeast cells in this experiment is 2875000cells/mL.
References
http://people.oregonstate.edu/~weisv/Protocols/Symbiodinium/Cell%20Counts.pdf
http://en.wikipedia.org/wiki/Hemocytometer
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