Selectivity

In a cell, we have many membranes like plasma membrane and nuclear membrane. These membranes allow many substances to pass through them. This passage of materials will be specific and selective. Selectivity is an important concept in the conduction of ions. The ions are conducted through the membrane proteins. The selectivity filters help the selectivity process by allowing specific ions into it. The pathway or canal comprises an amino acid sequence and is constricted in nature. The selectivity factor formula is discussed based on its applications. The selectivity meaning is clearly understood with the help of an illustration.

Selectivity

We all know the cell structure, including the nucleus, cytoplasm, and other cell organelles. A plasma membrane and cell membrane cover this cell. It performs the passage of materials to and fro the cell. These membranes do not allow all the materials into the cell. It is very specific and selective in choosing the materials and letting them in.

The cell membrane is formed by the combination of amphipathic lipid molecules. The molecule’s diffusion is prevented through the hydrophobic barrier. However, the cell gets its active energy through the nutrients present in the environment. The conduction of ions or molecules occurs through catalysis. 

The ions are transferred based on the property of selectivity. It is nothing but the priority of certain elements or molecules entering the cell channel. The selective ion channels are of the following classes:

• Sodium (NA+)
• chloride(cl-)
• Proton ( H+)
• Calcium (Ca+)
• Potassium ( K+)

The selectivity happens randomly. The channels allow only a certain percentage of molecules with different properties. The membranes have a hydrophobic nature, which makes ion stabilisation, and the polar molecules orient themselves in this stabilisation. The polar molecules have ions that cannot penetrate the cell.

Stabilisation Process

The membrane proteins generate the pores in which the water is filled. This allows the stabilisation of ions. The stabilisation of ions occurs with the help of side chains, main chains, and secondary helix structures. These structures form a polar residue.

The water ions undergo diffusion and interfere with the membrane. This diffusion is called passive diffusion; it allows only particular components or ions inside or out of the cell. 

Rate limiting step

The membrane, which allows the diffusion of the ions into the cell easily, will allow the ions to come out more simply. This is the rate-limiting step of diffusion. 

Selectivity factor formula

The Selectivity factor is finding its application in various fields like chromatography, chemical reactions, and drug designing. The selectivity factor formula differs according to the applications. 

The selectivity can be formulated as the ratio of a mole of desired product dividing by the difference between the compound mole. It is a simple formula and depends on any factor. In ion theory, we can substitute our polar water molecule and its ion concentration.

Conclusion

In cell theory, selectivity is the quality of membranes to select or choose the ions to and fro the cell. It consists of the channel pore, which possesses the conduction pathway to support the selectivity property. The selectivity filter is a pathway or canal made up of an amino acid sequence and is constricted in nature. This specifies the different ions with the rate-limiting step. The selectivity factor formula is explained in terms of ion concentration of cell theory. The K+ ions diffusion makes us understand the selectivity meaning easily. Apart from K+, there are many ions conducted through the membrane in the cell.