Active transports are a biological process in which the cell invests a large amount of energy to transport an existing substance in the cell medium. This type of transport occurs against the concentration gradient, that is, from the place with the lowest concentration to the one with the highest concentration of the substance in question. Substances transported with energy expenditure are usually larger than those transported passively, among them are the ions of potassium, iron, sodium, calcium, hydrogen, among others, in addition to sugars and amino acids.
The best known among active transports is what happens in the call sodium and potassium pump. This pump can be found in all cells of organisms and it is this pump that generates nerve impulses for the individual's nervous system. The sodium and potassium pump ensures the conservation of concentration differences between sodium and potassium ions across the cell membrane. In addition, it also controls cell volume and if it weren't for this control many cells would be so turgid as to burst.
The sodium and potassium pump aims to increase the concentration of sodium ions (Na+) outside the cell and potassium ions (K+) inside the cell. Usually, the sodium ion concentration is already high outside the cell and the potassium ion concentration is already high inside the cell. It would be expected that sodium ions would enter and potassium ions would leave the cell, but this is not the case, as the transport occurs against the concentration gradient.
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Constantly sending these ions in and out of the cell causes the cell to expend energy in the form of ATP (adenosine triphosphate or adenosine triphosphate). With each activation of the sodium and potassium pump, three sodium ions bind to a carrier protein. The energy provided by ATP alters the shape of the protein and thus favors the exit of sodium ions. At the same time, two potassium ions bind to the protein which returns to its original shape when the ATP unglues itself and this drives the potassium ions into the cell.
In addition to the sodium and potassium pump, several other active transports take place in our body. Among them, the transport of glucose from the intestinal cells to the blood, after the digestion of carbohydrates.
Impairment of membrane transport can cause a condition called cystic fibrosis. It is an inherited human disease, caused by problems in a gene located on chromosome 7, which controls protein synthesis. CFTR, the regulator of the transport of chloride ions and water across lung and intestinal cell membranes. The lack of this protein causes the accumulation of mucus in the intestines and lungs, causing several symptoms in the patient, among they: malnutrition due to the lack of efficient absorption of nutrients in the intestine, breathing difficulties and infections bacterial.
People affected with this form of the disease rarely reach the age of thirty. This gene located on chromosome 7 is very mutable, with at least 900 mutations that caused the disease having been discovered, and therefore symptoms can vary widely between patients. A child will only have cystic fibrosis if he inherits the defective gene from both parents, this happens in 1 in 29 people.
Denisele Neuza Aline Flores Borges
Biologist and Master in Botany
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