2619978
Description
Flashcards by Charlotte Hewson, updated more than 1 year ago
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Created by Charlotte Hewson
over 11 years ago
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| Question | Answer |
| what are the two types of microscope? | light and electron |
| why are light microscopes bad? | they use long wavelength light rays |
| what is the resolution of a light microscope? | 0.2 um |
| why are electron microscopes better than light microscopes? | they use short wavelength beams |
| what is the resolution of an electron microscope? | 0.1 nm |
| how do you work out magnification? | size of image/size of object |
| what do you need to ensure when using the magnification equation? | all the length units are the same |
| what is resolution? | the minimum distance apart two objects can be in order to be seen as separate objects |
| what does the resolution of a microscope depend on? | the wavelength/form of radiation used |
| what will happen if you increase the magnification beyond the microscopes resolving power? | size of image will increase but will get more blurred |
| what is tissue placed in before it undergoes ultracentrifugation? | a cold isotonic buffer |
| why is it cold? | to reduce any enzyme activity that may break down the organelles |
| why does it need to be isotonic? | so the organelles don't burst/shrink due osmosis |
| why is it placed in a buffer? | to maintain a constant pH |
| what occurs immediately before ultracentrifugation? | homogenisation |
| what is homogenisation? | cells are broken up by a homogeniser (blender) |
| why do you homogenise the tissue? | to release organelles from cell |
| what is the resultant fluid called? | homogenate |
| what is then done to this fluid? | filtered to remove complete cells and large debris |
| what is ultracentrifugation? | where fragments of homogenate are separated by a centrifugal force |
| what is the process of ultracentrifugation? | tube of homogenate put in ultracentrifuge and spun |
| what is the order of organelles heaviest to lightest? | nuclei, mitochondria, lysosomes, ribosomes |
| what must be done each time the supernatant is spun to get the next heaviest ? | it must be spun at a faster speed for longer |
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