20 Examples of Active and Passive Transportation

Is named cell transport to the exchange of substances between the inside of the cell and the external environment in which it is found. For example: gas diffusion, sweating, phagocytosis, exocytosis. This occurs through the plasma membrane, which is a semipermeable barrier that delimits the cell.

Cell transport is vital for the intake of nutrients and substances dissolved in the medium, and the expulsion of residues or metabolized substances inside the cell, such as hormones or enzymes. According to its direction of displacement of matter and its energy cost, we will talk about:

Examples of passive transport

1. Dissolution in the phospholipid layer. Thus, numerous elements enter the cell, such as water, oxygen, carbon dioxide, fat-soluble vitamins, steroids, glycerin and alcohols low molecular weight.
2. Entrance through whole protein channels. Some ionic substances (with an electrical charge), such as sodium, potassium, calcium or bicarbonate, cross the membrane guided by channels and special proteins for this purpose, of very small size.
instagram story viewer
3. The renal glomeruli. They filter the blood in the kidneys, stripping it of urea, creatinine, and you go out, through an ultrafiltration process carried out by the capillaries, preventing the passage of larger elements and excreting the smaller ones thanks to the pressure of the medium itself.
4. Glucose absorption. The cells are always kept with a low concentration of glucose, causing it to always flow by diffusion into their interior. To do this, transporter proteins carry it in and then turn it into glucose-6-phosphate.
5. The action of insulin. Is hormone secreted by the pancreas enhances the diffusion of glucose in the blood into the cells, reducing the presence of sugar in blood, playing a role hemoregulator.
6. Gas diffusion. Simple diffusion allows entry of gases product of respiration, from the outside to the inside of the cells from its concentration in blood. In this way the CO is expelled₂ and oxygen is used.
7. Sweating. The excretion of sweat through the skin is carried out by osmosis: the liquid flows out and carries toxins and other substances with it.
8. Plant roots. They have selective membranes that allow the entry of water and other minerals into the plant, and then they send it to the leaves to photosynthesize.
9. Intestinal absorption. The epithelial cells of the intestine absorb water and other nutrients of fecal matter, without allowing its entry into the bloodstream. Said selectivity also occurs passively, through the electrolyte gradient.
10. The release of enzymes and hormones into the bloodstream. It is often produced by the mechanics of high intracellular concentration, at no cost of ATP.

Examples of active transport

1. Sodium-potassium pump. It is a cell membrane mechanism that allows, through a protein transporter, expel sodium from the interior of the cell and replace it with potassium, maintaining the gradients of ions (low sodium and abundant potassium) and convenient electrical polarity.
2. Calcium pump. Another transport protein present in the cell membrane, allows calcium to be carried against its electrochemical gradient, from the cytoplasm to the outside.
3. Phagocytosis. The white blood cells that make it possible to defend the organism incorporate, through sacs of their plasma membrane, the foreign particles that we will later expel.
4. PinocytosisAnother process of phagocytization, proceeds through invaginations in the membrane that allow the entry of environmental fluid. It is something that the ovum does during its maturation.
5. Exocytosis. Contrary to phagocytization, it expels elements of the cellular content through membranous sacs that move outwards, until they merge with the membrane and open outwards. This is how neurons communicate: transmitting ionic contents.
6. HIV infection. The AIDS virus enters cells by taking advantage of their membrane, binding to glycoproteins present in their outer layer (CD4 receptors) and actively penetrating their interior.
7. Transcytosis. Mix of endocytosis and exocytosis, allows the transport of substances from one medium to another, for example, from blood capillaries to surrounding tissues.
8. Sugar phototransferase. A typical process of certain bacteria What coli, which consists of chemically modifying the substrates inside to attract others by covalent bonding and thus save a lot of energy.
9. Iron uptake. Iron is taken up by many bacteria by secreting siderophores such as enterobactin, which binds to iron forming chelates and then is absorbed by affinity into the bacteria, where it is released the metal.
10. LDL uptake. This lipoprotein with cholesterol esters is captured by the cell thanks to the action of an apoprotein (B-100) that allows its entry to the membrane and subsequent decomposition into amino acids.