BIOL 111 Lecture Notes - Lecture 6: Nuclear Membrane, Cell Membrane, Cell Fractionation
Document Summary
Cell is the simplest collection of matter that can be alive. Cells related by descent from earlier cells. Cells usually too small to be seen by naked eye. Light microscope (lm): visible light is passed through a specimen and then through glass lenses. The lenses refract (bend) light magnifying the image. Can magnify effectively to about 1000x the size of the actual specimen. Various techniques enhance contrast and enable cell components to be stained or labeled. Resolution of standard lm is too low to study organelles, the membrane-enclosed in eukaryotic cells. 2 basic types are used to study subcellular structures. Scanning electron microscopes (sems): beam of electrons focused onto the surface of a specimen, provides images that look 3-d. Transmission electron microscopes (tems): a beam of electrons focused through a specimen. Tems used mainly to study the internal structure of cells. Cell fractionation: takes cells apart and separates the major organelles from one another.
