Pinocytosis is what?

Nutrients fall into the internal environment of cells due to active transport, in which special enzymes take part. In this case, two processes occur: pinocytosis and phagocytosis.

General characteristic of the process

Pinocytosis is a universal method of nutrition, which is characteristic for plant and animal cells. Its essence lies in the ingress of nutrients into the cell in a dissolved form. Phagocytosis is a similar process, but it absorbs solid particles.

It is known that pinocytosis is an important stimulus for the formation of lysosomes, and phagocytosis is important in the infection of cells with viruses. These two processes have much in common, so they are often combined under a common name - cytosis, or endocytosis, although pinocytosis is more common. If the substances, on the contrary, are removed from the cell, then they talk about exocytosis.

If we generalize, then we can say that pinocytosis is a process of absorbing a droplet of liquid by a cell.

Process Features

Immediately need to say that the cytosis depends on the temperature and can not pass at 2 ° C, as well as with the action of inhibitors of metabolism, for example, sodium fluoride.

With pinocytosis, outgrowths of cytoplasm are formed - pseudopodia, which merge with each other and envelop droplets of liquid. At the same time, bubbles are formed that separate from the cell membrane and begin to migrate through the cytoplasm, turning into a vacuole called a pinosome.

It should be noted that pinocytosis is also the result of contact of the cell with a suspension of viruses. In this case, vibrios are contained in the formed vesicles. It is here that they sometimes undergo the "undressing" stage. When large molecules of individual drugs are captured, invagination and the formation of a vesicle, the vacuoles, also take place, but this mechanism of drug transport is not of decisive importance. A greater influence on the absorption of pharmacological agents has their shape, degree of grinding, as well as the presence of concomitant diseases of the digestive system - gastritis, colitis or, for example, peptic ulcer disease.

Reabsorption of protein in renal tubules

Pinocytosis is an active mechanism for the reabsorption of proteins in the proximal parts of renal nephrons. In the course of it, the protein is attached to the brush border. At this point, the membrane is invaginated, forming a vial containing the protein molecule. When a protein is inside such a vial, it begins to decompose into amino acids, which later through the basolateral membrane enter the intercellular fluid. Since such transport requires energy, it is called active.

It is worth noting that there is the concept of maximum transport for substances that are actively reabsorbed. This process is associated with the maximum load of transport systems. It occurs when the number of compounds caught in the lumen of the renal tubules exceeds the capacity of the enzymes and transport proteins involved in the transfer.

As an example, one can also cite a violation of glucose reabsorption, which is observed in the proximal sinuous tubule. If the content of this substance exceeds the functional capacity of the kidneys, it begins to excrete in the urine (normal glucose is not detected).

The significance of pinocytosis

This process takes place in the renal tubules and intestinal epithelium. It is responsible for the absorption and reabsorption of many compounds (including proteins and fats), which is necessary for the normal functioning of the body.

In addition, pinocytosis occurs during the metabolism through the capillary wall. Thus, large molecules that are unable to penetrate the pores of small blood vessels are transferred by pinocytosis. In this case, the membrane of the capillary cell is invaginated, resulting in the formation of a vacuole, which surrounds the molecule. On the opposite side of the cell, the opposite process begins - an emiocytosis.

It should also be mentioned that pinocytosis is an important component of active transport and ionic deposition. It is he who is the main mechanism of penetration of cells of high molecular substances into the internal environment. In addition, it is the main way of penetration of animals or plant viruses into host cells.