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Lab 2
 

Lab 2

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    Lab 2 Lab 2 Document Transcript

    • October 27, 2013 PRACTICAL CELL BIOLOGY LAB 2 Cell dimension Learning objectives Cell dimension. Ocular and stage micrometer. Methods of determination cell dimension. Materials Microscope, stage micrometer, ocular micrometer, specimen, ruler and electron micrograph. Cell dimension To measure the length or diameter of cell or component of the cell such as organelles we need, an ocular micrometer which has a scale. This is simply a disc of glass upon which equally spaced divisions are etched. The scale may be divided into 50 subdivisions, or 100 subdivisions. If we want to use the ocular micrometer, we have to calibrate it against a fixed and known ruler, the stage micrometer. Stage micrometers also come in varying lengths, 1 or 2 mm long and subdivided into 0.01 mm (10 micrometer) lengths. Each objective lens will need to be calibrated independently. To use, simply superimpose the ocular micrometer onto the stage micrometer and note the relationship of the length of the ocular to the stage micrometer. At different magnifications, the stage micrometer changes, but the ocular micrometer is fixed in dimension. In reality, the stage micrometer is also fixed, and what is changing? it is the power of the magnification of the objective.
    • October 27, 2013 PRACTICAL CELL BIOLOGY LAB 2 Ocular micrometer An ocular micrometer is a glass disk that fits in a microscope eye piece that has a scale, which is used to measure the size of magnified objects. The physical length of the marks on the scale depends on the degree of magnification. Ocular micrometer
    • October 27, 2013 PRACTICAL CELL BIOLOGY LAB 2 Stage micrometer A stage micrometer is a ruler that is mounted on a microscope slide that it has units (millimeters (mm) or micrometers (µm)). Also we can say, it is a tiny ruler that you know the measurements of it, and you use it to calibrate the ocular micrometer. Stage micrometer
    • October 27, 2013 PRACTICAL CELL BIOLOGY LAB 2 Procedure • Place a stage micrometer on the microscope stage, and using the lowest magnification (4X), focus on the grid of the stage micrometer. • Place ocular micrometer in place of eye piece and rotate it. • Move the stage of microscope until you superimpose the lines of the ocular micrometer upon those of the stage micrometer. Fit the lines of the two micrometers at one end of the field, count the spaces of stage micrometer that fit with the length of scale on ocular micrometer.
    • October 27, 2013 • • • PRACTICAL CELL BIOLOGY LAB 2 You know that each division of the stage micrometer equal to 10 micrometers, and also you know how many ocular divisions are equivalent to one stage division, now you can calculate the number of micrometers in each space of the ocular scale. Repeat for 10X and 40X, and 100X. Record your calculations. With using of the calculated values for your ocular micrometer, determine the dimensions of the cells and structures found on your microscope slide.
    • October 27, 2013 PRACTICAL CELL BIOLOGY LAB 2 How can you determine the diameter of the structures of the electron micrograph ? 1. Find the magnification of the micrograph as follow magnification of the micrograph = length of the bar on micrograph / real value of the bar 2. You can find length of bar on micrograph by using ruler in millimeter then converted to micrometer by multiplying by 1000 (be careful with unit). 3. Real length of cell structure = length of cell structure on micrograph / magnification. Problem 1: At a magnification of 40x, a student measured 41 ocular micrometer divisions per millimeter. What is the distance, in micrometers, per ocular unit at 40x? Problem 2: It was found that the units on the ocular micrometer and the units on the stage micrometer matched up 40 units to 1.0 mm at 100 power. (So 40 ocular units equals 1.0 mm.) If the wing of a dead fruit fly was measured to be 2.5 ocular micrometer units at a magnification of 100, what is the length of the wing in mm? What do you think about the importance of determination of cell dimension?