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AP Biology
Organization of the Cell
| Question | Answer |
|---|---|
| cell theory | unifying concept that (1) cells are the basic living units of organization and function in all organisms, (2) that all cells come from other cells |
| homeostasis | an appropriate internal environment of a cell |
| plasma membrane | a structurally distinctive surface membrane that surrounds all cells |
| organelles | internal structures that are specialized to carry out metabolic activities such as converting energy into usable forms, synthesizing needed compounds, and manufacturing structures necessary for functioning and reproduction |
| microvilli | finger-like projections of the plasma membrane that can significantly increase the surface area for absorbing nutrients and other materials |
| light microscope (LM) | type of microscope used by most students, consists of a tube with glass lenses at each end, referred to as a compound microscope |
| magnification | ratio of the size of the image seen with the microscope to the actual size of the object |
| resolution | or resolving power, is the capacity to distinguish fine detail in an image, defined as the minimum distance between two points at which they can both been seen separately rather than a single blurred point |
| types of microscopes | 1. bright-field microscopy 2. phase contrast microscopy 3. fluorescence microscope 4. dark-field microscopy 5. differential-interference-contrast microscopy 6. confocal fluorescence microscope |
| electron microscope (EM) | developed in the 1950s, tool used to study the fine details or ultrastructure of cells, much more powerful than conventional microscopes |
| transmission electron microscopy (TEM) | specimen is embedded in plastic and cut into extraordinarily thin sections which is placed on a metal grid and an electron beam is passed through the specimen which then falls onto a photographic plate |
| scanning electron microscope (SEM) | specimen is coasted with thin film of gold or other metal,when electron beam strikes various points on surface of the specimen,secondary electrons are emitted whose intensity varies with contour of surface,recorded emission patterns give 3D pix of surface |
| cell fractionation | technique for purifying organelles |
| centrifuge | spinning device used for the separation of components, creates an extract into two fractions: the pellet (forms at the bottom of the tube and contains heavier material) and supernatant (liquid above the pellet that contains lighter particles) |
| differential centrifugation | supernatant is spun at successively higher speeds permitting various cell components to be separated on the basis of their different sizes and densities |
| density gradient centrifugation | resuspended pellet is placed in a layer on top of a density gradient and further purfied |
Created by:
crescenti
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