Cell Membrane Composition and Metabolic Rates

The cell membrane is a phospholipids bilayer which plays an important role in the functioning of cells and influences cells’ activities. In this respect, it is important to lay emphasis on the fact that the cell membrane primarily performs the function of the protection of the cell as it separates the interior of the cell from the outside environment. In such a context, the change of the composition of the cell membrane and its structure can influence consistently the functioning of the cell at large and its activities. At the same time, the cell membrane is vulnerable to the impact of the environment and the overall functioning of the organism affects the composition of the cell membrane and its functions. For instance, the change of diet in humans can lead to the change of the membrane composition and, therefore, influence its functions and metabolism rates. In such a way, it proves beyond a doubt that the cell membrane performs extremely important functions and defines the normal functioning of the cell, but the change in the membrane composition can influence substantially the cell’s activities.

In order to understand the role of the cell membrane and its impact on metabolism rates, it is necessary to dwell upon the cell membrane composition. In fact, the cell membrane is the biological membrane separating the interior of a cell from the outside environment. The cell membrane contains a variety of biological molecules, which are mainly lipids and proteins. In such a way, it is mainly lipids and proteins that compose the cell membrane. They are incorporated into a membrane with the help of different mechanisms. For instance, the composition of proteins and lipids can occur through the fusion of intercellular vesicles with the membrane, which can incorporate the vesicle membrane’s components into the cell membrane (Cohen, 1986). In addition, if a membrane is continuous with a tubular structure made of membrane material, then the material from the tube can be drawn into the membrane continuously (Burggren and Bemis, 1990).

Also, it is worth mentioning the fact that, although the concentration of membrane components in the aqueous phase is low, there is an exchange of molecules between the lipid aqueous phases (Burggren and Bemis, 1990).

As it has been already mentioned above, the cell membrane mainly consists of lipids and proteins. Lipids comprising the cell membrane may be divided into three distinct classes: phospholipids, glycolipids, and steroids. The amount of either type of lipids depends on the type of the cell. However, in the majority of cells, phospholipids prevail. In fact, 30# of the plasma membrane is lipid (Caldwell, 1992).

Proteins are also essential elements which comprise the cell membrane. In fact, along with lipids, proteins compose the cell membrane and are incorporated together. Similarly to lipids, there are different types of proteins that compose the cell membrane, but proteins are much diverse compared to lipids that compose the cell membrane. In this respect, it is possible to speak about a diversity of proteins that can compose the cell membrane, but similarly to lipids, proteins that compose the cell membrane mainly depend on the type of cell, which membrane they compose.

At the same time, it is worth mentioning the fact that the amount of proteins varies between species and according to function.

Nevertheless, proteins constitute an essential part of the cell membrane since the typical amount of proteins in the cell membrane is about 50%, which is more than the amount of lipids (Cohen, 1986). In such a context, the role of proteins can hardly be underestimated. For instance, approximately a third of the genes in yeast code are composed specifically by proteins, and this number is even higher in multicellular organisms. In fact, proteins perform very important functions, being a part of the cell membrane. To put it more precisely, it is due to proteins the cell-cell contact is possible and, therefore, cells can interact efficiently due to proteins, while the change in the amount of proteins can definitely have a negative impact not only on individual cells but also on cell-cell contacts and their interaction. In addition, proteins contribute to the cytoskeleton contact, signaling, enzyme activities, or transporting substances across the cell membrane.

Furthermore, it is important to lay emphasis on the fact that the cell membrane is mainly composed of proteins and lipids, but they are not the only elements that compose the cell. The cell membrane composition is complemented by carbohydrates, which comprise an essential part of the cell membrane, although their share in the overall structure of the cell membrane is lower compared to proteins and lipids. In fact, carbohydrates composing the cell membrane are predominantly glycoproteins (Gould, 1981). At the same time, it is worth mentioning the fact that no glycosylation occurs on membranes within the cell, but it occurs on the extracellular surface of the cell membrane (Fersht, 1998). In such a way, it is possible to estimate that glycosylation mainly refers to the outer or external layer of the cell membrane.

Basically, it is hardly possible to underestimate the function and significance of the cell membrane for the normal functioning and development of cells as well as its impact on the metabolism rates. The cell membrane is a bilayer in which are embedded the cell surface receptors that influence much of the cell’s activities. The composition of the membrane is regulated by the gene and environmental influences. Changes in the composition of the membrane lipids and proteins can influence metabolism rates. For instance, the change in the lipids of the cell membrane can affect the function of the cell by affecting the fluidity of the membrane and, therefore, physiochemical properties of the structures embedded in it (Fersht, 1998). The presence of polyunsaturated fatty acids rather than saturated fatty acids in the plasma membrane lipid bilayer increases membrane fluidity, but it is also quite possible that changes in the lipid composition can affect the function by altering the composition of the fatty acids released to be incorporated into the second messenger molecules, such as diacylglycerol, which mediate insulin receptor function (Lodish et al., 2004).

In such a way, the change in the amount of proteins and lipids, which means the change of the cell membrane composition, can influence substantially the metabolism rates. In fact, such changes can accelerate or slow down the metabolism rates depending on the essence of the change that occurs within the cell membrane and elements involved in the change. The fact of such impact is undeniable and it is very important to take the impact of the cell membrane composition on the metabolism rates because often environmental influences can provoke such changes. For instance, the change in the diet of an individual can provoke consistent changes in the cell membrane composition, especially if the impact of the diet persists for a long period of time and is systematic. As a result, under the impact of the diet, the cell membrane composition can change leading to significant changes in the metabolism rates (Caldwell, 1992). Therefore, the understanding of close interdependence between the cell membrane composition and the metabolism rates is very important.

Thus, taking into account all above mentioned, it is possible to conclude that the cell membrane composition affects metabolism rates.

Basically, the cell membrane is composed of lipids and proteins. There are different types of lipids and proteins which depend on the type of the cell which membrane they form. In addition, there are carbohydrates, which though mainly compose the outer layer of the cell membrane. All the elements of the cell membrane are closely intertwined and together they compose the cell membrane and define the functions the cell membrane performs. At the same time, it is important to lay emphasis on the fact that the change in the amount of lipids or proteins which compose the cell membrane can lead to consistent changes in the metabolism rates and affect the overall functions of the cell.