Methods For Studying Cells In The Lab :: essays research papers

Methods for studying cells in the lab Centrifugation A centrifuge is a device for separating particles from a solution according to their size, shape, density, viscosity of the medium and rotor speed. Centrifugation can be used to separate cells from one culture or to isolate an organelle from the rest of the cell. The process relies on speed; the faster and longer the particle is centrifuged, the smaller the particles are that will be separated. Separation occurs by causing the larger particles to separate to the bottom as a particle or pellet, and the smaller will remain suspended in the liquid, or supernatant. Due to smaller particles separating out first, centrifugation is often done in small steps so that the supernatant takes off all larger unwanted cells first. The basic process of centrifugation: 1) The tissue must be homogenized to allow it to separate. 2) A salt solution is added to the sample and together they are placed in the centrifuge. 3) The centrifuge is run once for every group of cellular bodies that need to be separated and the pellet is removed. 4) This supernatant is removed after each centrifuge until the time and speed that you need to remove your specific product is obtained. The last centrifuge done will remove specific products that are wanted specifically. The speed determines this, and all of the lager products must be centrifuged out first. The pellet contains what the researcher wants to study, and contains progressively smaller particles as it is separated out. The supernatant becomes progressively clearer until virtually all of the particles are removed. Density Centrifugation Although simple centrifugation removes most cell particles separately, at certain speeds particles with similar densities and particle size will all be removed at once. A different method is needed to remove these. Density centrifugation removes particles according to their density rather than their approximate size. Density centrifugation is much like normal centrifugation other than the re-suspended pellet is placed in a test tube containing at least 10 layers of glucose.