Passive transport is the movement of ions and substances of atoms or other molecules across the cell membrane without the need for energy input. Unlike active transport, it does not require cellular energy input because it is driven by the tendency of the system to grow in entropy. Passive transport levels depend on the permeability of the cell membrane, which, in turn, depends on the organization and characteristics of the membrane lipids and proteins. The four main types of passive transport are simple diffusion, facilitated diffusion, filtration, and/or osmosis.
Video Passive transport
Diffusion
Diffusion is the net movement of materials from high concentration areas to areas of low concentration. The difference in concentration between the two regions is often referred to as concentration gradient , and the diffusion will continue until this gradient has been eliminated. Because diffusion transfers materials from a higher concentration area to a lower concentration area, it is described as a "dissolved concentration gradient" dissolved motion (compared to active transport, which often removes materials from low concentration areas to higher concentration areas, and because it is referred to as moving material "against the concentration gradient"). However, in many cases (eg passive drug transport) the driving force of passive transport can not be simplified to the concentration gradient. If there are different solutions on both sides of the membrane with different equilibrium solubility of the drug, the difference in saturation level is the driving force of passive membrane transport. This also applies to saturated solutions that are more and more important because of the spread of amorphous solid dispersion applications for increased availability of drug bioavailability.
Diffusion and simple osmosis are similar in some ways. A simple diffusion is the passive movement of solutes from high concentrations to lower concentrations until the concentration of the solute is uniform throughout and reaches equilibrium. Osmosis is very similar to simple diffusion but specifically describes the movement of water (not a solute) across a selectively permeable membrane until there is the same water concentration and the solute on either side of the membrane. Diffusion and simple osmosis are both passive forms of transport and require no ATP energy cells.
Maps Passive transport
Facilitated diffusion
Facilitated diffusion, also called carrier-mediated osmosis, is the movement of molecules across the cell membrane through a special transport protein which is the embryonic plasma membrane by actively taking or removing ions. Active transport of protons by H ATPase alters the membrane potential that allows passively facilitated transport of certain ions such as Potassium to decrease its gradient charge through transporters and high affinity channels.
Filtration
Filtration is the movement of water and solute molecules across the cell membrane due to the hydrostatic pressure generated by the cardiovascular system. Depending on the size of the membrane pores, only a certain size of solute can pass through. For example, the pores of Bowman's capsule membrane in the kidney are very small, and only albumin, the smallest protein, has a chance to be filtered. On the other hand, the pores of membranes of the liver cells are very large, but do not forget the very small cells to allow various solutes to pass through and be metabolized.
Osmosis
Osmosis is the movement of water molecules across the permeable selective membrane. The net movement of water molecules through a permeable membrane is partly from a high water potential solution to areas with low water potential. Cells with less negative water potential will attract water but this depends on other factors such as dissolved potential (pressure in cells such as dissolved molecules) and potential pressure (external pressure eg cell wall). There are three types of Osmosis solutions: isotonic solutions, hypotonic solutions, and hypertonic solutions. The isotonic solution is when the concentration of extracellular solute is offset by the concentration inside the cell. In Isotonic solutions, water molecules are still moving between solutions, but the level is the same from both directions, so that water movements are balanced between the inside of the cell and also outside the cell. The hypotonic solution is when the concentration of solute outside the cell is lower than the concentration inside the cell. In a hypotonic solution, water moves to cells, down the concentration gradient (from higher water concentrations to lower ones). It can cause cells to swell. Cells that do not have cell walls, such as animal cells, can explode in this solution. The hypertonic solution is when the concentration of the solute is higher (think hyper - high) than the concentration inside the cell. In a hypertonic solution, water will move out , causing the cell to shrink.
See also
- Active transport
- Transport phenomenon
References
Source of the article : Wikipedia
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