Structure of Plasma Membrane-Free-Samples-Myassignmenthelp.com

Question: Discuss about the Plasma membrane structure. Answer: The plasma membranedefines boundary of a cell and separates it into two primary fluid compartments namely, intracellular fluidinside cells and extracellular fluid outside cells. It is made up of lipid bilayer that forms the basic structure of the membrane, and is largely composed ofphospholipids, with traces of cholesterol, glycolipids,and lipid rafts. A phospholipid molecule contains a hydrophilic phosphate group/head on one end, and hydrophobic chains of fatty acids that make up the tails. The lipid tails are composed of saturated or unsaturated fatty acids. Owing to the fact that the phospholipids contain both hydrophilic and hydrophobic regions, the lipid bilayer is termed as amphipathic (Ingo?lfsson et al., 2014). However, most often it gets interrupted by several proteins. Two proteins commonly related to the plasma membrane are namely, integral/intrinsic or extrinsic/peripheral proteins. Theintegral proteins are found to remain embedded in the plasma membrane. Peripheral prote insare located on the outer or inner surface of the bilayer. However, they are also found attached to the surfaces of the integral proteins. Figure 1- Plasma membrane structure Source- (Nicolson, 2014) Owing to the rigid ring structures, cholesterol is found to play an essential role in maintaining structure of the membrane. It creates a difference on fluidity of the membrane by interfering with movement of the fatty acid chain and lowering fluidity, at high temperatures. Carbohydrates (glycoproteins) are also present in the plasma membrane and play an essential role in cell-to-cell recognition (Nicolson, 2014). Several substances such as, oxygen and carbon dioxide gases are found to easily diffuse through phospholipid bilayer.Oxygen is present in high concentration outside the cells. The structure of phospholipid bilayer creates provisons for the uncharged, small oxygen molecules to pass through the plasma membrane, by the process of simple diffusion, to the region of their lower concentration. Thus, oxygen moves down its concentration gradient, without expenditure of energy (Stein, 2012). On the other hand, the process of facilitated diffusion brings about movement of sodium ions, with the assistance of special channel proteins. Na+ ions are concentrated outside the cells, and cannot pass through the bilayer due to their charge. Membrane proteins form Na+ pores/channels and help the ions move along the concentration gradient to the interior. This kind of diffusion is a passive process. Hence, there is no energy expenditure by the cell. In addition, theNa+/K+ATPase pump helps in transporting out Na+ of a cell while facilitating movement of K+ inside the cells (Stein, 2012).Thus, the lipid bilayer is found to form the foundation of the plasma membrane. References Ingo?lfsson, H. I., Melo, M. N., Van Eerden, F. J., Arnarez, C., Lopez, C. A., Wassenaar, T. A., ... Marrink, S. J. (2014). Lipid organization of the plasma membrane.Journal of the american chemical society,136(41), 14554-14559. DOI:10.1021/ja507832e Nicolson, G. L. (2014). The FluidMosaic Model of Membrane Structure: Still relevant to understanding the structure, function and dynamics of biological membranes after more than 40years.Biochimica et Biophysica Acta (BBA)-Biomembranes,1838(6), 1451-1466. https://doi.org/10.1016/j.bbamem.2013.10.019 Stein, W. (2012).The movement of molecules across cell membranes(Vol. 6). Elsevier, 126-176. Retrieved from- https://books.google.co.in/books?hl=enlr=id=Ncs0DzQjwPECoi=fndpg=PP1dq=Stein,+W.+(2012).+The+movement+of+molecules+across+cell+membranes+(Vol.+6).+Elsevier,+126-176.ots=l4mlnVnFbBsig=hulFixH3H5F-l2D5VKnMwEJB9Rs#v=onepageqf=false Stein, W. (2012).Transport and diffusion across cell membranes. Elsevier, 69-112. Retrieved from- https://books.google.co.in/books?hl=enlr=id=yeFbTJl_8PcCoi=fndpg=PP1dq=Stein,+W.+(2012).+Transport+and+diffusion+across+cell+membranes.+Elsevier,+69-112.ots=ulO4etR7rqsig=hLXB0yu1FzayTMSfljyOo3V-FbA#v=onepageqf=fals