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Introduction

Moving sodium and potassium ions across the cell membrane is an active transport mechanism that requires ATP hydrolysis to provide the necessary energy.


Na + /K + -ATPase is one of the enzymes involved. The enormous surplus of Na +  outside the cell and the big excess of K + ions inside the cell is maintained by this process. It accomplishes the transfer of three Na + to the cell's exterior and two K + ions to the cell's interior.


The separation of charge across the membrane is aided by this imbalanced charge transfer. The sodium-potassium pump contributes significantly to the action potential generated by nerve cells. 


This pump is known as a P-type ion pump because ATP interacts with the transport protein, causing it to phosphorylate and change its conformation.


Functions, Structure and Uses

Structure

The Na+-K+ pump is a P-type ATPase that resembles the H+-K+-ATPase and the sarco(endo) plasmic reticulum Ca2+-ATPase in structure.


The sodium-potassium pump is a transmembrane protein that is divided into three subunits. The 3 subunits are:

  • α-Subunit- It is the largest subunit that contains the binding sites for Na+, K+, and ATP.

  • β-Subunit- A single-spanning membrane protein having a transmembrane α-helix and a glycosylated extracellular domain.

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Function

  • The sodium-potassium pump is responsible for transporting ions into and out of cells. It contributes to the maintenance of a cell's resting potential both during and after stimulation. The cell membrane's potential is determined by maintaining a low concentration of sodium and a high concentration of potassium within the cell.

  • Many secondary active transporters (transport proteins in the membrane) are activated by Na export and are responsible for transporting amino acids, glucose, and other essential nutrients.

  • The sodium-potassium pump maintains cellular osmolarity, which regulates cell volume. Osmosis regulates cell volume. This function maintains and controls the concentration of various nutrients and chemical substances.

  • Extracellular signaling is also carried out with the help of sodium-potassium ATPase.

  • The sodium and potassium pumps govern the intrinsic activity of neurons, therefore influencing the activity state.


Uses

The function of the Na K ATPase can be used to design and administer medications to human physiology. It means that specific medication molecules can be directed to specific organs to treat specific diseases.


More About the Topic

The tissues are made of characteristic cells that maintain their internal physiology in different ways. One of the most fascinating ways to maintain the concentration of potassium and sodium ions inside a cell is the sodium potassium pump. It is a protein present in many cells that maintain the Na-K balance between the cell and body fluids. In this section, we will discuss what the sodium potassium ATPase pump is and its functions elaborately.


What is Sodium Potassium Atpase?

Sodium potassium pump or Na K ATPase is a protein-based enzyme present in the cell membrane of the animals that manages and controls the concentration of sodium and potassium inside the cell. The full name of this electrogenic transmembrane ATPase is Sodium Potassium Adenosine Triphosphate. It has different functions in the cell physiology of animals.


As per the sodium potassium pump definition, this is a protein enzyme present in the cell membrane. It utilizes ATP as energy currency to transport Na and K ions. For every ATP molecule, it exports 3 Na+ ions and imports 2 K+ ions. It concludes that a single positively charged ion is excessively exported in every pump cycle. This pump cycle was discovered by Jens Christian Skou, a Nobel laureate, in the year 1957.


Due to his discovery, the movement of the ions inside and outside the cells became absolutely clear. In fact, the excitation process of nerve cells also depends on the action of these pumps present in the cell membrane.


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Mechanism of Sodium Potassium Pump

As per the structure of this electrogenic transmembrane ATPase, it has more affinity towards Na+. This is why it binds with 3 Na+ ions inside the cell. Due to phosphorylation, ADP is released and a change occurs in the pump. This change exposes Na+ ions in the extracellular space. ADP has more affinity towards K+ ions. When 2 K+ ions are bound with the ADP, dephosphorylation occurs releasing these ions inside the cells. It results in the formation of ATP thus repeating the process. This is how the sodium potassium ATPase pump works in the cell membrane controlling the ionic concentration.


Functions of Sodium Potassium Pump

As per cell physiology, the sodium potassium pump is of four different types in mammals. They all are isoforms but have unique tissue expressions and properties. The entire family is a part of P-Type ATPase. Here is a list of the sodium potassium pump function in the animal cells.

  • Resting Potential: Sodium potassium pump transports ions in and out of the cells. It helps in maintaining the resting potential of a cell during and after its excitation. The potential of the cell membrane is decided by maintaining a low concentration of Na and a high concentration of K inside the cell.


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  • Reversal Potential: Despite having the same charge, Na+ and K+ have differences in equilibrium potential in extracellular and intracellular concentrations. Sodium potassium pump transports ions inside and outside maintaining equilibrium for the proper functioning of different cells.

  • Transport: The Na exportation drives many secondary active transporters (transport proteins in the membrane) which are responsible for the transportation of amino acids, glucose, and important nutrients.

  • Cell Volume Control: The sodium potassium pump mechanism also helps in regulating the cell volume by maintaining cellular osmolarity. It means that the cell volume is regulated with the help of osmosis. Proper concentration of different nutrients and other organic compounds are maintained and controlled using this function.

  • Signal Transduction: Extracellular signal-transducing is also conducted with the help of sodium potassium ATPase.

  • Neuron Activity State: It has been found that the intrinsic activities of neurons are controlled by the sodium and potassium pump thus controlling the activity state.


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How Can it be Used for Drug Administration?

The Na K ATPase function can be used for designing and administering drugs to human physiology. The definition and structure of these pumps differ. It means that specific drug molecules can be targeted to particular organs for the remedy of certain ailments. For instance, cardiac glycosides target the NA-K pump present in the cells of the heart muscles.


Similarly, muscular contraction depends on the Ca++ ions. It is different from the sodium potassium pump but has similar functions. Specific drug molecules are designed to target muscles for proper acceptance and action.


Conclusion

From the above section, we learned that every animal cell has different types of Na K pumps that connect the intracellular and extracellular fluids. The osmotic regulation of a cell depends on these pumps.


The sodium potassium pump ratio, as mentioned above, is the prime function of this protein enzyme present in the cell membrane of different animal cells. Its functions are quite important for cellular physiology and the functioning of the tissues. By studying the structure and mode of operation of this pump, many pharmacological compounds can be designed to target specific tissues and organs for remedies.

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FAQs on Sodium Potassium Pump

1. What is the Sodium Potassium Pump Structure?

As per the cytology of the cell membrane, the sodium potassium pump is a protein-based electrogenic transmembrane ATPase that connects the intracellular and extracellular fluids. It helps in maintaining the ionic concentration of the cells, their volume and is responsible for the absorption of nutrients such as glucose, amino acids, etc.

2. What is the difference between ATP and ADP?

Adenosine Triphosphate is the energy currency of animal cells. It is used by the Na K ATPase enzyme present in the cell membrane for exporting Na+ ions. Due to phosphorylation, ATP converts to ADP that kicks in K+ ions inside the cells. Due to dephosphorylation, ADP converts to ATP. This is the basic difference between ATP and ADP in this case.

3. Why is Na-K ATPase Important?

The channel between the extracellular and intracellular space is maintained by the sodium potassium pump ratio. It helps in maintaining cellular osmolarity, cellular volume, importing nutrients, exporting unnecessary materials, etc. This enzyme also serves as a selective channel for regulating the concentration of various compounds inside the cells and promotes cellular functions in different organs.

4. What is the role of Sodium And Potassium in conduction?

Water does not have the power to conduct electricity in its pure state. The transmission of electricity through water is facilitated by sodium and potassium ions, as well as other electrolytes found in the body.


These ions circulate in and out of the cell. They conduct electricity every time they move. In the human body, electrolyte equilibrium is extremely important.


A high salt intake combined with a low potassium intake increases the risk of mortality and heart disease. Making the correct food diet choices is critical for maintaining a healthy body.

5. What is the daily use of Sodium?

The use of Sodium in daily life is as follows:

  • Every day, the average individual consumes sodium in the form of table salt in their food. 

  • The cooling nuclear reactor also makes use of sodium.

  • Baking soda is a leavening agent used in the preparation of dishes such as pancakes, cakes, and bread.

  • Sodium salts are found in many soaps.

  • De-icing, medicine, organic chemistry, and street lights are among the other applications.

6. How Potassium is used in real-life?

  • Potassium chloride (KCl), which is used to manufacture fertilisers, is the most common usage of potassium.

  • Potassium is necessary for plant development.

  • Soaps, detergents, gold mining, dyes, glass production, gunpowder, and batteries are just a few of the industrial uses for potassium.

  • Potassium is also essential in our systems. It is used to contract muscles.

7. Explain β-Subunit in detail?

The β-subunit is a membrane protein with a transmembrane α-helix and a glycosylated extracellular domain that spans a single membrane. 


This subunit binds to the M7 and M10 helices of the -subunit within the lipid bilayer using a cluster of aromatic residues. These residues also come into contact with a cholesterol molecule, which is required for ion transport to take place. 


Contact between the α and β subunits can also be found in the extracellular domains at various residues. The β-subunit is responsible for directing the polypeptide to the membrane and maintaining its stability. It contributes to the binding selectivity of potassium ions.

8. Explain α-Subunit in detail?

The α-subunit is the biggest subunit and contains the Na+, K+, and ATP binding sites. There are ten transmembrane α-helices in this subunit (M1-M10). M4-M6 creates a three-helix bundle around which these helices are centred. 


The transmembrane helices include the binding sites for K+ and Na+. On the cytoplasmic face of the membrane, there are three functional domains: the actuator domain (A), the nucleotide-binding domain (N), and the phosphorylation domain (P). 


The α-subunit has four known isoforms, yet even the two most diverse isoforms share 78% sequence identity. The N-terminus, the first extracellular loop, and the third cytosolic domain have the most structural variability among the isoforms. The pace of ion transport and the ability to operate as a signalling receptor can be affected by this variability.


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