F211 Biology Questions
Module 1 Cells 1. State the resolution and magnification that can be achieved by a light microscope. * The maximum magnification that can be achieved by a light microscope is x1500 and the maximum resolution is 200nm. The limit of resolution is due to the magnitude of the wavelength of light. Two objects can be distinguished only if light waves can pass between them. 2. Explain the difference between magnification and resolution. * Magnification is the degree to which the size of an image is larger than the object itself, whereas resolution is the degree to which it is possible distinguish between two objects. 3. Explain the need for staining samples in light microscopy. * Staining is used in light microscopy to make the specimens visible because some biological material is colourless. 4. Calculate the linear magnification of an image such as a photomicrograph or electron micrograph. * Actual Size = Image Size / Magnification * Magnification = Image Size / Actual Size * Image Size = Actual Size x Magnification

Unit | Symbol | Equivalent in Metres | Fraction of a Metre | Metre | m | 1 | one | Decimetre | dm | 0.1 | one tenth | Centimetre | cm | 0.01 | one hundredth | Millimetre | mm | 0.001 | one thousandth | Micrometre | µm | 0.000 001 | one millionth | Nanometre | nm | 0.000 000 001 | one thousand millionth |

5. State the resolution and magnification that can be achieved with the electron microscope. * The maximum magnification that can be achieved using a Transmission Electron Microscope (TEM) is x500 000, whereas using a Scanning Electron Microscope (SEM) is x100 000. The maximum resolution is 0.2nm. 6. Explain the need for staining samples for use in electron microscopy. * Staining is used in electron microscopy to make the specimens visible to the human eye. 7. Explain the importance of the cytoskeleton in providing mechanical strength to cells, aiding transport within cells and enabling cell movement. * Cells contain fibres made of protein.