Active transport in a cell
What is - definition
Active transport is the energy used by cells to transport substances across their plasma membrane.
Active transport process and main features.
This process involves a carrier protein called a pump, which performs transport by carrying a substance across the cell membrane from a lower concentration area to a higher concentration area.
As we saw above, this transport requires energy from the cell, which in turn spends approximately 40% of its ATP (free energy stock in the cell) in this process.
In addition to this function, the protein pump also acts as an enzyme, which in turn breaks down ATP. By expelling sodium ions (Na +) and introducing potassium ions (K +), this protein is also known as the sodium potassium pump (Na + / K +).
All cells have thousands of bombs like these on their plasma membranes. This large amount is due to its great importance, because it is through them that it is possible to maintain a low concentration of sodium ions in the cytosol and, in contrast, a higher concentration of potassium ions.
Cytosol is the fluid that fills the cytoplasm, the space between the plasma membrane and the nucleus, which contains cytoplasmic sacs, channels and organelles.
However, at the same time as sodium is expelled, potassium is introduced into cells. These concentrations maintained constantly through active transport, as we have seen, require a lot of energy from the cell, as these ions are always transported to the region of their highest concentration.
The opposite occurs in passive transport (diffusion and osmosis), because in this case, the highest concentration of solvent or solute will always go to the area of lowest concentration.