The process of repolarization involves the movement of K + (Potassium ions) into the nerve against the expulsion of Na + (Sodium ion). ![]() In the nerve cell, the conduction of nerve impulses occurs by polarization, depolarization, and repolarization processes. why is membrane transport vital for normal cell function?Īns: In a normal cell, membrane transport is vital for the movement of glucose and amino acids into the cells for the production of energy and protein synthesis, respectively. The removal of waste matter from the inside occurs through the reverse process. The lysosomes bind to these vacuoles and release the lysosomal enzymes, which digest the material inside the vacuole. In this process, the solid material is entrapped in a membranous vacuole. Solid engulfment is called phagocytosis (cell eating), while for the liquid, it is called pinocytosis (Cell drinking). Here the particle is engulfed in the cytoplasm. But for large particles, the transport occurs by bulk transport. The above-described methods are suitable for small-size molecules. For this, excess Na+ is kept on higher levels by being constantly pumped out in exchange for K+. But due to the concentration gradient, the ions tend to move to the other side. Na+ is higher in concentration on the outside of the cell, while K+ is in higher concentration on the inside. This method is said to use 30% of cellular ATP requirements. However, the mechanism involves the movement of one sodium ion into an exchange of potassium ions outside. Here the movement of solutes occurs by the use of energy in the form of ATP. This is of the following types like Sodium potassium pump So, this is against the concentration gradient, and hence, chemical energy in the form of ATP is spent. In this process, the substances move from one region with a high concentration to another with a low concentration across the cell membrane. However, in the next methods, transport across the membrane occurs through the use of energy (ATP). Thus, in all the above three methods, like passive diffusion, facilitated diffusion, and osmosis, there is no energy spent on transport. Like diffusion, this osmosis occurs until the equilibrium is reached. When the solute molecules are large and unable to diffuse, this osmosis occurs. Here the water molecules move from a region of lower solute concentration to a region of higher solute concentration. ![]() This process is similar to diffusion, but here instead of the solute, the solvent moves down the concentration gradient. This limitation of the number of molecules that can be transported in a given time is called transport maximum. ![]() Hence, the rate of transport is dependent on the availability of free carrier proteins. ![]() The carrier channels are specific for one particular substance and also are limited. When the substance molecules bind, the carrier protein changes its shape so that the molecules move to the other end of the channel in the protein.Įxamples of substances using this route are glucose and amino acids. (right to the left).įor this, specialized carrier protein molecules help in moving substances from one side of the membrane to the other. Glucose molecules move to the other side of the membrane by facilitated diffusion.
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