It is called cell transport to the exchange of substances between the cell interior and the external environment in which it is located. This occurs through the plasma membrane, which is a semipermeable barrier that delimits the cell.
Cellular transport is vital for the entry of nutrients and dissolved substances into the environment, and the expulsion of residues or metabolized substances inside the cell, such as hormones or enzymes. According to its direction of movement of matter and its energy cost, we will talk about:
- Passive transport. By favoring the concentration gradient, that is, from a more concentrated medium to one less, it occurs by diffusion through the membrane and has no energy cost, since it takes advantage of the random movements of the molecules (their kinetic energy ).
Types of Passive transport
There are four types of passive transport:
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- Simple diffusion. The material goes from the most concentrated to the least concentrated area until the levels are equal.
- Dissemination facilitated. Transport is carried out by special transport proteins found inside the cell membrane.
- Filtration. The plasma membrane has pores through which material of a certain specific size can leak into it, by hydrostatic pressure.
- Osmosis . Similar to simple diffusion, it depends on the passage of water molecules through the membrane, due to the pressure of the medium itself and its selectivity.
- Active transport. Unlike the passive, it works against the concentration gradient (from a less concentrated area to a more concentrated one), so it has a cost of cellular energy. This allows cells to accumulate the material they need for their synthesis processes.
