How Is a Cells Membrane Suited to Its Functions free essay sample

Each phospholipid is composed of a non-polar (hydrophobic) region of two fatty acids pointing inwards and a polar (hydrophilic) phosphorylated alcohol head region pointing outwards on the exterior of the membrane. Connecting the phosphorylated alcohol and both fatty acids is a 3-carbon compound called glycerol. Since there is both a hydrophilic and a hydrophobic region of each phospholipid, then the phospholipids are always arranged in a bilayer. The bilayer has two main strengths: it’s fluidity and its selectively permeable structure. The layer tends to be fluid or flexible since the fatty acid areas do not attract each other very strongly. This is one of the strengths of the cell membrane since it allows animal cells to have a variable shape and also allows the process of endocytosis (allows macromolecules3 to enter the cell). This fluidity influences membrane transport and is dependent on two things: the specific structure of the fatty acid chains and the temperature. We will write a custom essay sample on How Is a Cells Membrane Suited to Its Functions? or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page If the fatty acid chains are closer together then the bilayer will become more viscous and less fluid. If the temperature is lower, then the fluidity will increase. Another strength of the phospholipid bilayer is that because of the selectively permeable structure, large molecules and small polar molecules cannot cross it without assistance from other structures. Without this feature, the cell membrane would let any kind of materials in and out of the cell. This could potentially damage the cell. Among phospholipids and fatty acids, the membrane also contains various types of proteins (integral proteins and peripheral proteins). The phospholipid bilayer contains two types of proteins: integral and peripheral. Both proteins are essential since they allow for interactions to occur between cells. They can also serve as a hormone binding site, create enzymatic action, provide cell adhesion, generate cell-to-cell communication, contain channels for passive transport or pumps for active transport. Integral proteins are located within the lipid bilayer but have an area found on the exterior as well. This means that they have both a hydrophilic region and a hydrophobic region. The hydrophobic area holds the protein in place whilst the hydrophilic area is exposed to water solutions on either side of the membrane. Additionally they can float reasonably freely but cannot be removed without the aid of harsh chemicals such as detergents, which destroy the lipid bilayer. The most common type of integral protein is the transmembrane protein, which extends through the exterior as well as the interior of the bilayer. As a result, they are the only proteins, which are able to perform jobs both inside and outside of the cell. There are multiple kinds of transmembrane proteins such as channel proteins. These proteins aid the transportation of polar substances (particularly ions and carbohydrates) across the membrane through passive transport4. Other non-polar substances may be transported directly through the bilayer. This also includes water. Another example of a transmembrane protein is a carrier protein, which only recognizes one substance or a group of similar substances. Unlike a channel protein, the carrier protein uses active transport5 to move ions, small molecules or macromolecules across a membrane. They may also use facilitated diffusion6 instead of active transport. The movement of substances across the membrane through this protein, whether using active transport or facilitated diffusion, is referred to as carrier mediated transport. Unlike integral proteins, peripheral proteins do not extend into the hydrophobic region of the bilayer but remain bound to the surface of the membrane. They are often anchored to an integral protein and are also easier to analyze for scientists since they may be extracted without damaging the lipid bilayer. Proteins such as glycoproteins may be attached to peripheral proteins and are involved in immune response and recognition of like cells. This makes the role of the peripheral proteins more important. In conclusion, aspects of the cell’s membrane structure make it better suited for its functions. This is because each protein, cholesterol and phospholipid, which makes up a cell membrane, plays an important role in supporting and protecting the cell. Without the proteins for example, the cell would not be able to control which molecules enter and exit and would also have less enzyme activity. Additionally the cell would not be able to act as a receptor. Without cholesterol, the membrane would not be able to function at various temperatures, which would affect the fluidity of the membrane. Lastly, without the phospholipid bilayer, there would be no solvent for substances and proteins within the membrane and also no site for proteins and lipid molecules to diffuse through to get into the cell. Furthermore without the cell membrane, there would be nothing to protect the cell or to decide what enters or exits. Glossary: 1. Selectively Permeable: A selectively permeable membrane, also called a partially permeable membrane, only allows certain substances to pass through. 2. Homeostasis: Maintaining a constant internal environment. 3. Macromolecules: A very large molecule. 4. Passive Transport: Material moves from an area of high concentration to an area of low concentration. 5. Active Transport: Substance is moved against a concentration gradient, so energy (ATP) expenditure must occur. 6. Facilitated Diffusion: A type of diffusion involving a membrane with specific carrier proteins that are capable of combing with the substance to aid in movement.