BIOL 101 Lecture Notes - Lecture 4: Electron Microscope, Cell Membrane, Small Cell
21 Jan 2019
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Document Summary
Nearly all require a microscope to be seen. Each type in our body is specialized for a particular function. Can only see down to cellular level. Overcomes limitations by using beam of electrons. Need surface areas large enough for entry and exit of materials. Small cells have more surface area for exchange. Adaptations to increase surface area: microvilli in the small intestine increase surface area for absorption of nutrients. Marks boundary between outside and inside a cell and regulates passage in and out of a cell. Phospholipid bilayer with embedded proteins: polar heads (hydrophilic) of phospholipids face into watery medium, nonpolar tails (hydrophobic) face another. Fluid-mosaic model- the structure of the plasma membrane. Channel proteins: form tunnel for specific molecules. Involved in passage of molecule through the membrane, sometimes requiring input of energy. Enables our body to distinguish btwn our own cells and cells of other organisms. Allow signal molecules to bind, causing a cellular response.
