Mechanism and Function of Sodium Potassium Pump in Cells

TRANSPORT OF SUBSTANCES ACTIVELY USING MEMBRANES

Sometimes, even though there is a little quantity of a drug in the extracellular fluid, a large concentration is needed in the intracellular fluid. For potassium ions, for instance, this is the case. On the other hand, although the concentrations of other ions are large in the extracellular fluid, it is crucial to maintain very low concentrations of these ions inside the cell. With sodium ions in particular, this is the case. Since simple diffusion eventually brings concentrations on both sides of the membrane into equilibrium, neither of these two effects could result from it. Rather, an energy source needs to induce an excess of potassium ions to enter cells and an excess of sodium ions to exit cells. Active transport is the process by which molecules or ions are moved upward against a concentration gradient (or uphill against an electrical or pressure gradient) by a cell membrane. Several different sugars, the majority of amino acids, hydrogen, potassium, calcium, iron, hydrogen ions, chloride, iodide, and urate ions are examples of molecules that are actively transported through at least some cell membranes.

Two types of active transportation are primary and secondary

Depending on where the energy for facilitating the travel comes from, there are two forms of active transport: main active transport and secondary active transport. The breakdown of adenosine triphosphate (ATP) or another high-energy phosphate compound provides the energy for main active transport. Energy that has been stored as ionic concentration differences of secondary molecular or ionic substances between the two sides of a cell membrane originally produced by primary active transport is obtained secondarily in secondary active transport. As with assisted diffusion, transport in both scenarios is dependent on carrier proteins that pierce the cell membrane. Because it may provide energy to the transported material to move it against the electrochemical gradient, the carrier protein in active transport differs from that in assisted diffusion. Examples of primary and secondary active transport, together with more thorough explanations of their underlying principles of operation, are given in the ensuing sections.

First Active Transportation

Potassium is transported into cells and sodium is transported out of them via the sodium-potassium pump. Primary active transport carries a number of chemicals, including ions such as sodium, potassium, calcium, hydrogen, and chloride. The sodium-potassium (Na⁺-K⁺) pump, a transporter that simultaneously pumps potassium ions from the outside to the inside of all cells while pushing sodium ions forth through cell membranes, is the active transport mechanism that has been examined. This pump is in charge of creating a negative electrical voltage inside the cells and preserving the variations in sodium and potassium concentrations across the cell membrane. By transferring nerve impulses throughout the neurological system, this pump serves as the foundation for nerve activity.

Mechanism of Na⁺-K⁺Pump Functioning

The Na⁺-K⁺ pump's fundamental physical parts. The carrier protein is a complex made up of two different globular proteins: the ẞ subunit, which has a molecular weight of approximately 55,000, and the bigger a subunit, which has a molecular weight of approximately 100,000. The larger protein possesses three unique characteristics that are crucial for the pump to work, even if the smaller protein's role is unknown (except from the possibility that it anchors the protein complex in the lipid membrane):

1. On the part of the protein that extends into the cell, there are three binding sites for sodium ions.
2. Its exterior contains two binding sites for potassium ions.
3. This protein's core contains adenosine triphosphatase (ATPase) activity at the sodium binding sites.

When two potassium ions attach to the carrier protein's outside and three sodium ions attach to its interior, the protein's ATPase activity is activated. One ATP molecule is converted to adenosine diphosphate (ADP) and a high-energy phosphate bond of energy is released upon activation of ATPase. The released energy is hypothesized to cause a chemical and structural change in the protein carrier molecule, causing it to extrude three sodium ions outside and two potassium ions inside.

The Na⁺-K⁺ ATPase pump has the same reverse functionality as other enzymes

The Na⁺-K⁺ pump will create ATP from ADP and phosphate if the electrochemical gradients for Na⁺ and K⁺ are experimentally raised to the point where the energy contained in the gradients is larger than the chemical energy of ATP hydrolysis. At that point, the ions will migrate down their concentration gradients. Therefore, the phosphorylated version of the Na⁺-K+ pump can either use the energy to change its conformation and pump K⁺ into the cell and Na⁺ out of the cell, or it can use the energy to donate its phosphate to ADP to make ATP. The direction of the enzyme reaction is determined by the electrochemical gradients for Na⁺ and K⁺ as well as the relative amounts of ATP, ADP, and phosphate. For certain cells, such nerve cells that are electrically active. The following is the method used to adjust the loudness. Numerous proteins and other chemical compounds that are unable to leave the cell are found inside.

Na⁺-K⁺ Pump Regulates Cell Volume

Due to their negative charge, the majority of these proteins and other organic molecules draw a lot of potassium, sodium, and other positive ions. Water then enters the cell by osmosis as a result of all these molecules and ions. The cell will continue to enlarge indefinitely until it explodes if this process is not stopped. The Na⁺-K⁺ pump is the typical mechanism that prevents this from happening. Recall that for every two K⁺ ions pumped to the inside of the cell, this process pumps three Na⁺ ions to the exterior. Furthermore, compared to potassium ions, sodium ions are significantly less permeable across the membrane, and once they are outside, they tend to stay there. As a result, this mechanism causes a net loss of ions from the cell and starts the process of water osmosis. The Na⁺-K⁺ pump is automatically triggered when a cell starts to expand for whatever reason; this causes additional ions to be transported outside and to carry water with them. As a result, the Na⁺-K⁺ pump continuously monitors cell volume to keep it within normal limits.

Nature of the Na⁺-K⁺Pump Is Electrogenic

A net of one positive charge is transferred from the inside of the cell to the outside of the cell for each pump cycle because the Na⁺-K⁺ pump transports three Na ions to the exterior for every two K⁺ ions that are pushed to the interior. This process produces positivity externally but creates an inside deficiency of positive ions, resulting in negativity. Because the Na⁺-K⁺ pump generates an electrical potential across the cell membrane, it is therefore referred to be electrogenic. In order for neuron and muscle fibers to conduct nerve and muscle messages, they must possess this electrical potential.