AQA Biology 3.1 Investigating the structure of cells

Charlotte Hewson
Flashcards by Charlotte Hewson, updated more than 1 year ago
Charlotte Hewson
Created by Charlotte Hewson almost 6 years ago


AS - Level AS Biology (unit 1 - 03. cells and the movement in and out of them) Flashcards on AQA Biology 3.1 Investigating the structure of cells, created by Charlotte Hewson on 04/29/2015.

Resource summary

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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