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a) Simple Diffusion b) Facilitated Diffusion c) Osmosis (water only). 2) Active a) Molecules b) Particles. Diffusion. Diffusion is the net passive movement of. In diffusion there is no challenge involved as it is along the concentration gradient, but in active transport movement of molecules occur against. The key thing here is to note that both diffusion and osmosis are passive processes, and active transport is an active process. A passive process i.
The difference of concentration between the two areas is often termed as the concentration gradientand diffusion will continue until this gradient has been eliminated. Since diffusion moves materials from an area of higher concentration to an area of lower concentration, it is described as moving solutes "down the concentration gradient" compared with active transportwhich often moves material from area of low concentration to area of higher concentration, and therefore referred to as moving the material "against the concentration gradient".
However, in many cases e. If there are different solutions at the two sides of the membrane with different equilibrium solubility of the drug, the difference in degree of saturation is the driving force of passive membrane transport. Simple diffusion and osmosis are in some ways similar. Simple diffusion is the passive movement of solute from a high concentration to a lower concentration until the concentration of the solute is uniform throughout and reaches equilibrium.
Osmosis is much like simple diffusion but it specifically describes the movement of water not the solute across a selectively permeable membrane until there is an equal concentration of water and solute on both sides of the membrane.
Simple diffusion and osmosis are both forms of passive transport and require none of the cell's ATP energy. Facilitated diffusion Depiction of facilitated diffusion. Facilitated diffusion, also called carrier-mediated osmosis, is the movement of molecules across the cell membrane via special transport proteins that are embedded in the plasma membrane by actively taking up or excluding ions. Filtration and Ultrafiltration renal Filtration.
Filtration is movement of water and solute molecules across the cell membrane due to hydrostatic pressure generated by the cardiovascular system. Depending on the size of the membrane pores, only solutes of a certain size may pass through it. For example, the membrane pores of the Bowman's capsule in the kidneys are very small, and only albuminsthe smallest of the proteins, have any chance of being filtered through. On the other hand, the membrane pores of liver cells are extremely large, but not forgetting cells are extremely small to allow a variety of solutes to pass through and be metabolized.
Covers selective permeability of membranes, diffusion, and facilitated diffusion including channels and carrier proteins. Introduction Have you been through airport security lately? Flight attendants, captains, and airport personnel travel through quickly via a special channel, while regular passengers pass through more slowly, sometimes with a long wait in line.
In many ways, airport security is a lot like the plasma membrane of a cell. Cell membranes are selectively permeable, regulating which substances can pass through, as well as how much of each substance can enter or exit at a given time. The simplest forms of transport across a membrane are passive.
Passive transport does not require the cell to expend any energy and involves a substance diffusing down its concentration gradient across a membrane.
A concentration gradient is a just a region of space over which the concentration of a substance changes, and substances will naturally move down their gradients, from an area of higher to an area of lower concentration. In cells, some molecules can move down their concentration gradients by crossing the lipid portion of the membrane directly, while others must pass through membrane proteins in a process called facilitated diffusion.
Diffusion and passive transport
Selective permeability The phospholipids of plasma membranes are amphipathic: The hydrophobic core of the plasma membrane helps some materials move through the membrane, while it blocks the movement of others. Structure of a phospholipid, showing hydrophobic fatty acid tails and hydrophilic hea.
A bilayered membrane consisting of phospholipids arranged in two layers, with their heads pointing out and their tails sandwiched in the middle, is also shown.
Image modified from OpenStax Biology. Polar and charged molecules have much more trouble crossing the membrane. Polar molecules can easily interact with the outer face of the membrane, where the negatively charged head groups are found, but they have difficulty passing through its hydrophobic core.
Passive Transport - Taking the Easy Road
Water molecules, for instance, cannot cross the membrane rapidly although thanks to their small size and lack of a full charge, they can cross at a slow rate. Additionally, while small ions are the right size to slip through the membrane, their charge prevents them from doing so. Larger charged and polar molecules, like sugars and amino acids, also need help from proteins to efficiently cross the membrane.
Diffusion In the process of diffusion, a substance tends to move from an area of high concentration to an area of low concentration until its concentration becomes equal throughout a space.
Simple diffusion and passive transport (article) | Khan Academy
For example, think about someone opening a bottle of cleaning ammonia in the middle of a room. The ammonia molecules will initially be most concentrated right where the person opened the bottle, with few or no molecules at the edges of the room.
Ultimately, if the bottle is capped and the room is closed, the ammonia molecules will become evenly distributed throughout its volume. The same will happen with molecules of any type: This process does not require any energy input; in fact, a concentration gradient itself is a form of stored potential energy, and this energy is used up as the concentrations equalize. Image showing the process of diffusion across the plasma membrane.