Concentration Gradient

A gradient is a relationship between a change in one variable, such as concentration, pressure, or temperature, and a change in distance. A concentration gradient is a change in concentration over a distance; a pressure gradient is a change in pressure over a distance; and a temperature gradient is a change in temperature over a distance. 

The process of concentration gradient occurs when the concentration of the solute is more in one place than in others. The concentration gradient is reduced by diffusion; however, membranes can prevent diffusion and preserve a concentration gradient. 

Concentration Gradient Meaning

The word “concentration” means the amount of solute in the given solvent. For example, if salt is put in a water tank, the concentration of that area must be higher where the salt has just been dumped than the area where there is no salt diffused; therefore, the concentration gradient is in the tank.

With time, the solute will mix in the whole tank, and the concentration gradient will try to make an equal concentration throughout the tank. Hence, the concentration gradient will disappear when the salt diffuses throughout the solution in the tank.

If the small uncharged molecules are concentrated in one region outside the plasma membrane, but with time, the molecules start to migrate from the region of high concentration to the region of lower concentration. This is called diffusion. At one time, the molecules tend to be dispersed equally in the cytoplasm and outside the cytoplasm to equal the concentration on both sides.

Examples of Concentration Gradient

ATP synthase

Some life forms, in order to energise living activities, rely on the tendency of molecules to move from high concentration to lower concentration. ATP synthase uses the concentration gradient of added hydrogen ions to generate ATP. When the hydrogen ion comes across ATP synthase, the ATP synthase adds a phosphate group to ADP, thus allowing the energy to be stored in a newly-formed bond.

Neurons and the sodium-potassium pump

The sodium potassium pump is an important concentration gradient in neurons for human life. During cell communications, the iron gates are open, which allows the passing of sodium and potassium. The travelling of electrochemical signals is very fast. The electrochemical signals are very important because they allow us to think, perceive, and respond. The result is that the potassium concentration is high inside the nerve cell and the sodium concentration higher outside the cell.

Glucose sodium symport pump

Sodium glucose symporter is found on the Apical membrane of the epithelial cells. The sodium and glucose bind to the symporter and are simultaneously both co-transported into the epithelial cells. Since glucose is a large molecule, its diffusion across a membrane is difficult. Hence, it diffuses across membranes through facilitated diffusion, down the concentration gradient.

Lungs and Gills

Lungs and gills both use the process of the concentration gradient. Oxygen obeys the rule of the concentration gradient. It moves to diffuse from a high concentration region to a lower concentration region, and thus, it goes into our lungs or the gills of fish which fulfil our need for oxygen.

The Function of  Concentration Gradient

Concentration gradient has many functions that are important for life.

Many cells use concentration gradients to perform various tasks. Concentration gradient stores energy, and that energy can be used to complete various functions of cells.

Neurons use the concentration gradient for the movement of potassium and sodium ions through and into the nerve cells.

Concentration gradient helps in the movement of oxygen in the low oxygen blood because oxygen moves from high concentration to lower concentration.

The same gills also use a concentration gradient to absorb the oxygen from water to the blood of fishes.

It also helps in the diffusion of large molecules which are difficult to pass through the membrane. 

Conclusion

Concentration gradient is the change of variable with the distance. The variables can be the pressure, temperature, and concentration of any substance. Concentration gradient happens when the solute is added to a solution, and it is concentrated in one place, but with time, the molecule tends to move from a high concentration area to lower concentration area. Thus, diffusion occurs. Concentration gradient has many functions in living cells and other solutions. Glucose potassium transport, sodium potassium transport, and the transport of oxygen into lungs and gills are some examples of the concentration gradient.