What is the Fluid Mosaic Model of Cell Membrane and How to Download a PDF Version
The fluid mosaic model is a widely accepted theory that describes the structure and function of biological membranes. According to this model, membranes are composed of a double layer of phospholipid molecules, in which various proteins and carbohydrates are embedded. The phospholipid layer acts as a barrier to the diffusion of polar solutes, while the proteins and carbohydrates perform various roles such as transport, recognition, signaling, and adhesion. The term \"fluid\" refers to the ability of the membrane components to move laterally within the plane of the membrane, while the term \"mosaic\" reflects the diversity and arrangement of these components.
The fluid mosaic model was proposed in 1972 by S.J. Singer and Garth Nicolson, based on experimental evidence from various techniques such as electron microscopy, fluorescence recovery after photobleaching, freeze-fracture microscopy, and X-ray diffraction. The model has been refined and updated over the years to incorporate new findings and concepts, such as membrane asymmetry, lipid rafts, membrane domains, and membrane curvature.
If you are interested in learning more about the fluid mosaic model of cell membrane, you can download a PDF version of the original paper by Singer and Nicolson from this link: https://www.researchgate.net/publication/18833326_The_Fluid_Mosaic_Model_of_the_Structure_of_Cell_Membranes. This paper provides a comprehensive overview of the model and its implications for membrane functions and phenomena. You can also find other PDF resources on this topic by searching on Google Scholar or other academic databases.
The main component of the plasma membrane is the phospholipid bilayer. Phospholipids are amphipathic molecules, meaning they have both a hydrophilic (water-loving) and a hydrophobic (water-fearing) part. The hydrophilic part is the phosphate head, which is polar and can form hydrogen bonds with water. The hydrophobic part is the fatty acid tail, which is nonpolar and cannot interact with water. In the phospholipid bilayer, the phospholipids are arranged in such a way that their hydrophilic heads face the aqueous environment on both sides of the membrane, while their hydrophobic tails are tucked inside, away from water. This arrangement allows the membrane to act as a selective barrier between the inside and outside of the cell.
Another important lipid component of the plasma membrane is cholesterol. Cholesterol is a steroid molecule that is mostly hydrophobic with a small hydrophilic region. Cholesterol molecules are inserted into the phospholipid bilayer, with their hydrophilic region aligned with the phospholipid heads and their hydrophobic region aligned with the phospholipid tails. Cholesterol helps to regulate the fluidity and stability of the membrane. At high temperatures, cholesterol reduces membrane fluidity by restraining the movement of phospholipids. At low temperatures, cholesterol prevents membrane solidification by disrupting the packing of phospholipids.
The plasma membrane also contains various proteins that perform different functions. Some proteins are integral, meaning they span across the entire membrane and have both an extracellular and an intracellular domain. Some proteins are peripheral, meaning they are attached to either the inner or outer surface of the membrane and do not penetrate into the hydrophobic core. Some proteins are anchored to the membrane by a lipid tail that is covalently attached to them. Proteins can be classified into different types based on their roles, such as transporters, receptors, enzymes, anchors, or identifiers.
Finally, the plasma membrane has carbohydrate groups that are attached to some of the lipids and proteins. These carbohydrate groups can be short chains of sugars (oligosaccharides) or longer chains of sugars (polysaccharides). The carbohydrate groups are always located on the outer surface of the plasma membrane, where they form a layer called the glycocalyx. The glycocalyx serves as a recognition site for other cells and molecules, such as hormones, antibodies, or pathogens. The glycocalyx also helps to protect the cell from mechanical and chemical damage. aa16f39245