Question

1) What is the purpose for using stains?

2) Why is it necessary to make a heat -fixed smear and what are the disadvantages of test fixing?
3) what is the benefit to using immersion oil when viewing bacteria?

4) When preparing a heat-fixed smear, what are some differences between liquid and solid. media?

5) Once oil has been added to your slide , which objective (s) can be used? cannot be used?

Answer 1

1. Staining of biological specimens is important to make them visible so that it can be observed under a microscope. It is not always important to stay a specimen, like cells containing chloroplast can be seen because they already contain green coloured chlorophyll pigment.

2. It is necessary to heat fix the cells on the surface of a slide because if we will not do so, then while washing the slide with buffer and adding different stain, the cells will be lost. But the disadvantage is that the cells on the slide can be burnt in doing so.

3. If we use oil immersion lenses while viewing any specimen, like bacteria, then the refractive index of the medium increases which increases the resolution of the image being formed.

4. For heat fixation of liquid culture, we add one drop of culture and then spread it uniformly all over the slide and then heat it. For heat fixation of solid medium, we pour the liquid form of this medium uniformly on the slide and let it cool to solidify. We than heat it for heat fixation.

5. 100x is to used, 4x, 10x are not used

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