Functions of cell membrane

Cell membranes, also known as Plasma membranes, are often referred to as structural units of life. These are present in almost every cell of living species. The cell membrane presents in the form of a bubble-like shape. Although, detaching the interior and exterior of cells is the primary function of the cell membrane. It also helps the cell to connect to its surrounding environment systematically. 

The plasma membrane consists of a semipermeable lipid layer responsible for transferring movements of substances inside and outside the cell. They even exclude some specific substances in a certain amount. Also, the cell membranes identify and communicate with other cells and share the required details.  

The write-up covers components, structures and functions of membranes you will need to know. 

Components of Cell membranes 

A cell membrane or plasma membrane consists of three major components, i.e., phospholipids, protein and carbohydrates. The components freely shift from one place to another at the membrane plane. Often, the proportion of these components varies on the different types of cells. Proteins share 50% mass composition, phospholipids share 40%, and carbohydrates share the remaining 10%. The components are- 

• Phospholipids- Phospholipids consist of one head group and two acid tails that connect to the phosphate. The cell membranes containing two phospholipid layers point the tail inwards. Such arrangement of layers is known as the phospholipid bilayer. 
• Protein-Protein membrane carries the ability to extend the plasma membrane. It allows the proteins to simultaneously connect slowly with the inner and outer surface. 
• Carbohydrates- The carbohydrates groups obtain from the cell membrane’s outer surface. It connects with proteins to generate glycoproteins and lipids, resulting in the formation of glycolipids. 

Structure of cell membrane

• Cell membranes consist of the fluid mosaic model. The model was introduced by S.J singer and G.L Nicolson in 1902 to provide a basic structure of cell membranes. 
• The bilayer of phospholipids, along with their fatty hydrophobic acid tails, are resistant to ions and water molecules. It crosses the membranes through pumps, carriers and transmembrane channels. On the one hand, the head is hydrophilic and polar; on the other hand, tails are hydrophobic and nonpolar.  
• The transmembrane nutrifies the cells with nutrients to set up the potential of transmembrane electricals and balance the internal ions.  
• A slight change in amino acid in any single channel or plasma membrane results in cystic fibrosis human disease. Thus, based on the membrane locations in the body, lipids can produce 20-80% membrane and leave the rest in proteins. 

Functions of cell membranes 

Cell membranes that are responsible for enclosing and defining cells perform the following functions –

• Cell membranes are semipermeable and thus allows the molecules to disperse across lipid layers. The small hydrophobic molecules and gases like carbon dioxide and oxygen can significantly cross the membranes. Likewise, the polar molecules can also slowly pass through membranes, including water and ethanol. 
• Plasma membranes act as a barrier in the diffusion process of highly charged and extensive molecules. Highly charged molecules contain ions, whereas large molecules include amino acids and sugars inside them. Although, the movement of some specific proteins submerged in the membrane defines the passage of both the molecules. 
• Proteins that transfer during the cell membrane function are specific and selective. Therefore, they consume energy to translate the passages. Moreover, proteins shift specific nutrients at odds with gradients, requiring extra energy. Thus, cell membranes regulate the concentration gradient and transfer the materials for the health and maintenance of their cells.
• Cell membranes help in holding the cytoskeleton in places. Often, few proteins extend their support and connect with cytoskeletal fibres to balance and define the shape of various cells. 
• Plasma membrane prevents its cells from toxic chemicals in environmental exposure. Consequently, it is also an essential function of the cell membrane.  
• It also guards the cells against losing biological macromolecules present inside the membrane. 
• Also, it maintains the physical integrity of the cells, being the primary function of cell membranes. 
• Sometimes, the cell membranes communicate with their adjacent cell membranes to generate plants and animal tissues. 
• The receptor sites in the function of cell membranes allow interacting with certain biochemicals like immune proteins, neurotransmitters, hormones. 
• The proteins and enzymes structure of the plasma membrane is responsible for the operation of metabolic procedure in the membrane. 

Diverse nature of cell membranes

• The eukaryotic cells also contain intercellular membranes surrounding several organelles like prokaryotic cells. The cell membranes are diverse, owing to their extensive endomembrane system. It includes the nuclear membrane, lysosomes, Golgi apparatus and endoplasmic reticulum. Eventually, their components interchange in a systematic way at the endomembrane system. 
• An example of this will be the Golgi apparatus, and the endoplasmic reticulum possesses different configurations. Proteins that ground in these membranes serves molecular zip codes to identify the final objective. 
• Often the chloroplasts and mitochondria have an unusual membrane structure. The organelles consist of two membranes, homogenous with the modern-day prokaryotes.

Conclusion

The lipids and proteins of the membranes act as barriers for some specific intracellular organelles. It can sustain the outer and inner molecules, like the way they are. Henceforth, it allows the molecules to cross molecular events present in the cells. The main components of the cell membranes comprise phospholipids, carbohydrates and proteins. These components share different proportions varying in the type of cell they present. 

The semipermeable nature of the cell membrane permits the molecules to disperse the lipid layers. Often, sustaining the physical integrity of cells remains the cell membrane’s principal function. Moreover, the endomembrane system allows the components to interchange in an organised manner, thus maintaining the diversity of the cells.