Difference between Cell Membrane and Plasma Membrane

Cell membrane and plasma membrane are the outer covers of cells and composed of lipids, which is made up of lipids, proteins, carbohydrates and nucleic acids. cell membrane and plasma membrane both are composed of lipids, which is a substance that has only one common feature, they both are composed of lipids. It is important to note that the term lipid is used in a large sense to describe a multitude of compounds including triacylglycerols, phospholipids and sphingolipids.

Based on the view point of origin, cell membrane and plasma membrane can be seen as a type of organelle membranes.

Cell membrane: 

It is an integral part of the cell envelope and contains proteins but more importantly it contains specialised glycoproteins called lipoproteins. These lipoproteins can only be found in biological membranes. Lipoprotein is a carrier protein that has proteins in it, which make it an integral part of the plasma membrane that surrounds cells. These lipoproteins are responsible for transporting substances within and between cells, without these lipoproteins there is no existence of cells.

Functions of Cell Membrane

1) Helps to maintain normal hydration of cells by allowing water, ions and sugar molecules (importance of sugar will be explained in detail in a later section) to pass through the cell membrane.

2) It is responsible for the channels that are present on the plasma membrane. The channel proteins, which allow these substances to pass through the plasma membrane. 

3) It is also responsible for causing certain metabolic processes by providing specific sites for certain enzymes and permeability factors to induce certain metabolic processes.

Plasma Membrane

It is composed of lipoproteins and phospholipids, which makes it an integral part of the cell envelope. Plasma Membrane can be described as a semi permeable membrane. It has different types of proteins embedded in it. These proteins include channel proteins, which are always present in plasma membranes. This is the reason why we call them semi permeable membranes.

Significance of Plasma Membrane

1) It can be seen as a distinguishable membrane because of the presence of different types of protein embedded in it.

2) It is responsible for maintaining the normal hydration and ionic composition of cells.

3) It also plays an important role in stimulating certain metabolic pathways involving certain enzymes, due to this plasma membranes have a direct connection with mitochondria.

Functions of Plasma Membrane

1) It helps to maintain the normal hydration level because it contains proteins such as aquaporins and ion channels that allow water, ions and sugar molecules to pass through cells.

2) It plays an important role in transporting specific sugars between cells, which helps further promote metabolic processes taking place inside the cell.

3) It is a semi permeable membrane, which transports substances between the cell and the extracellular environment.

4) It contains lipoproteins that are responsible for transport in & out of cells.

5) It has channels, proteins and proteins embedded in it, that pass specific substances through the cell membrane. These channels & proteins play an important role in transporting sugar molecules (importance of sugar will be explained in detail later in this article).

Difference between Cell Membrane and Plasma Membrane

1) The membrane lipids present in plasma membranes are phospholipids while they are present in cell membranes it is the other way around.

2) Cell membrane has certain channels and proteins embedded in it which are responsible for determining the passage of specific substances in & out of cells. On the other hand plasma membrane does not have any such features.

3) Cell membranes rich in lipids present in plasma membranes, whereas plasma membranes rich in lipids present only in cell membranes.

4) Plasma membrane is found only on the outer surfaces of the cells while plasma membranes can also be found on inner surfaces inside the cell nucleus region.

5) Plasma membrane is semi permeable while plasma membrane is not semi permeable.

6) Cell membrane contains proteins embedded as well as specific channels embedded within its structure.

7) Cell membrane can be found in most of the cell types while plasma membrane is present only on the outside surfaces of cells.

Different substances need to pass through cell membranes to further promote metabolic processes taking place in the cell. These substances include amino acids, carbohydrates, water and ions. Cell membranes play an important role in allowing these substances to pass by providing specific sites for enzyme factors and permeability factors for passage of these substances. It is with the help of specific proteins embedded within the membrane that these substrates are transported throughout and are transported inside & outside the cells, which play a significant role in metabolic processes. This process is known as diffusion.

Conclusion

Cell Membrane and Plasma Membrane are the two types of membrane found in cells. Cell membrane is an integral part of the cell envelope while plasma membrane is a part of the cell surface. Plasma membranes are less permeable than cell membranes, which is why they do not allow transport of specific compounds like ions, amino acids and proteins. Cell membrane contains channels and proteins embedded into it as well as specific sites for enzyme factors to further promote metabolic processes taking place inside the cell. Cell membranes are rich in lipids present in plasma membranes, whereas plasma membranes only present in certain cells due to differences between their structure.

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