Passive transport examples
- Dissolution in the phospholipid layer. Thus, numerous elements enter the cell, such as water, oxygen, carbon dioxide, fat-soluble vitamins, steroids, glycerin, and low molecular weight alcohols.
- Entrance for integral protein channels. Some ionic substances (with an electric charge), such as sodium, potassium, calcium, or bicarbonate, pass through the membrane guided by channels and special proteins for this, of very small size.
- The renal glomeruli. They filter the blood in the kidneys, stripping it of urea, creatinine, and salts, through an ultrafiltration process carried out by the capillaries, preventing the passage of larger elements and excreting the smallest ones thanks to the medium’s own pressure.
- Glucose absorption. The cells are always maintained with a low concentration of glucose, causing it to always flow by diffusion into it. To do this, transport proteins carry it inwards and then turn it glucose-6-phosphate.
- The action of insulin . This hormone secreted by the pancreas enhances the diffusion of blood glucose into the cells, reducing the presence of blood sugar, fulfilling a thermoregulatory role.
- Gas diffusion. Simple diffusion allows the entry of gases from respiration, from the exterior to the interior of the cells from their concentration in blood. In this way, CO 2 is expelled and oxygen is used.
- 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.
- The roots of the plants. They have selective membranes that allow water and other minerals to enter the plant, and then send it to the leaves to photosynthesize.
- Intestinal absorption. The intestine’s epithelial cells absorb water and other nutrients from the stool, without allowing it to enter the bloodstream. Said selectivity also occurs passively, through the electrolytic gradient.
- The release of enzymes and hormones into the bloodstream. It is often produced by the mechanics of high intracellular concentration, with no cost of ATP.
See Also: Active Transport Vs Passive transport