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Recommended: Osmosis
Diffusion and Osmosis Across Dialysis Tubing
By Jasper Lee, Leo Zhao, Oliva Skopas, Alistair Dobson, and Alex Bell
11/15/13
Purpose: The purpose of this experiment was to demonstrate the principles of diffusion and osmosis, two processes that are essential for life, by using dialysis tubing (a semi-permeable membrane) to simulate the cell membrane and observe said processes.
Introduction: Diffusion is the movement of molecules from a higher concentration to a lower concentration. Imagine you had a glass of water and put a drop of food coloring in. The molecules of food coloring would move from the initial site of the drop, which has an high concentration of the coloring, to the rest of the water, which has a low concentration. Eventually, the food coloring will spread out so that the entire glass of water has an equal concentration of it. At this point, the glass of water is in dynamic equilibrium - that is, the average concentration of the food coloring throughout the water is the same. Molecules are always moving, so there will be times when the food coloring happens to converge on one spot and leads to a higher concentration. However, on average the concentration is relatively equal. Osmosis is similar to diffusion, in that it is the movement of molecules from a high to low concentration. However, there are two major differences. The first one is that osmosis is the movement of water exclusively - the movement of any other molecule besides it is not considered osmosis. The second one is that osmosis is the movement of water across a selectively permeable membrane. A selectively permeable membrane is one that allows certain molecules through and blocks others. Whether or not a molecule can pass through the membrane usu...
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...velop, decreasing the accuracy of the experiment. While the simulations was generally accurate, there were major limitations that sharply decreased the similarity between it and the cell.
Works Cited
Brooklyn College. "Fluid Mosaic Model of Plasma Membrane." Fluid Mosaic Model of Plasma Membrane. Brooklyn College, n.d. Web. 16 Nov. 2013. .
National Kidney Foundation. "Dialysis." The National Kidney Foundation: A to Z Health Guide. National Kidney Foundation, n.d. Web. 16 Nov. 2013. .
Schmidt, Andrea. "Concentration Gradients." Concentration Gradients. MIT, n.d. Web. 16 Nov. 2013. .
Active transport requires the use of energy because substances are moved against/up a concentration gradient or across a partially permeable membrane. On the other hand, passive transport moves molecules down the concentration gradient and does not require cellular energy. For example, osmosis which is the movement of water across the membrane would be considered a passive transport because the molecules, or in this case water move easy and freely.
The Effect of Solute Concentration on the Rate of Osmosis Aim: To test and observe how the concentration gradient between a potato and water & sugar solution will affect the rate of osmosis. Introduction: Osmosis is defined as, diffusion, or net movement, of free water molecules from high to low concentration through a semi-permeable membrane. When a substance, such as sugar (which we will be using in the experiment we are about to analyse), dissolves in water, it attracts free water molecules to itself, and in doing so, stops them from moving freely. The effect of this, is that the concentration of (free) water molecules in that environment goes down. There are less free water molecules, and therefore less water molecules to pass across a semi-permeable membrane, through which sugar molecules and other molecules attached to them are too big to diffuse across with ease.
This cell membrane plays an important part in Diffusion. Cell membrane and Diffusion Diffusion is the movement of the molecules of gas or liquids from a higher concentrated region to a lower concentration through the partially permeable cell membrane along a concentraion gradient. This explanation is in the diagram shown below: [IMAGE] Turgor When a plant cell is placed in a dilute solution or a less concentrated solution then the water particles pass through the partially permeable membrane and fill the cell up with water. The cell then becomes Turgor or hard. An example of this is a strong well-watered plant.
If the concentration of one side of the membrane is greater than the molecules will travel from the higher to lower concentration. Eventually there will be a dynamic equilibrium and there will be no net movement of molecules from one side to the other. Osmosis is the diffusion of water. Like diffusion, the water moves from a region of higher water potential to a region of lower water potential.
“The plasma membrane is the edge of life, the boundary that separates the living cell from its nonliving surroundings. The plasma membrane is a remarkable film, so thin that you would have to stack 8,000 of these membranes to equal the thickness of the page you are reading. Yet the plasma membrane can regulate the traffic of chemicals into and out of the cell. The key to how a membrane works is its structure” (Simon, 02/2012, p. 60).
...ous cytoplasm in the physical confirmation that was proposed. Same as if oil and water being left to stand, after being shaken will separate, meaning the hydrophilic and hydrophobic elements will sort themselves out into the correct order to isolate them from contact with the polar components. They supported their theories with both physical and biochemical evidence. During research they had successfully took apart the bilayers of frozen cell membranes from different areas to show the proteins embedded inside, other evidence had also shown to support that transmembrane proteins exist.
The first type of dialysis I will talk about is peritoneal dialysis. Peritoneal dialysis must be done every day. This dialysis takes place in the abdomen, which has a semi-permeable membrane. Solutions enter into the abdomen and are left for an amount of time. The solution helps to collect and clean the body of impurities. The solution, which flows into the peritoneal cavity, is c...
The Importance of Diffusion to Living Organisms Diffusion is basically the movement of chemical species (ions or molecules) under the influence of concentration difference. The species will move from the high concentration area to the low concentration area till the concentration is consistent in the whole system. Diffusion mostly occurs in gases and liquids as these can move freely. The main features of an efficient diffusion system would be that it has a large surface area, thin membrane and a continuous supply of substances. A large surface area is needed so that high amount of substances can be exchanged at a time while the thin membrane means that the diffusion pathway would be short so that it is more efficient.
there would be no flow of water into or out of the cell so the cell
- The nurse’s mistake will increase the saltiness due to the double amount of saline in the bag.
Most cell membranes are like that, being permeable to water and some solutes only. Osmosis is therefore the diffusion of water through a partially permeable membrane. The basic principles of diffusion apply here.
π is equal to the osmotic pressure, V is equal to the cell volume and B is the intracellular solids (Hall). Ponder’s R value is the ratio of intracellular solvent volume to the water in its environment; R=(Vi -b)/W. These two equations are related because Ponder’s R value is a measure of how much of an osmometer a cell is while the van’t Hoff relation shows what the osmotic pressure is, both inside and outside the cell. Overall cell membrane permeability can be measured by Ponder’s R value while the osmotic pressure differentials between the external environment and the internal environment are seen with the van’t Hoff relation (Hall). Cells evolved to become great osmometers, but not perfect osmometers, in order to provide a way for solutes to move along permeable membranes. The van’t Hoff relation permits organisms to live in environments of varying osmolarity because regulating solute concentration within a cell can increase or decrease the cell’s affinity for osmosis (Darnell et al). Ponder’s R value, on the other hand, shows how a cell can never become a perfect osmometer. If a cell could become a perfect osmometer, it could cause cell lysis or shrinkage of the cell (Hall). The avoidance of perfect osmometry can be seen within the human erythrocyte as a small portion of cell water will not take part in an osmotic exchange due to tonicity within its
The purpose of this lab was to see firsthand the diffusion of a substance across a selectively permeable membrane. Diffusion is the movement of molecules from an area of high concentration to an area of lower concentration until both concentrations are equal, or as you could more professionally call it, equilibrium. This concept is one that we have been studying in depth currently in Biology class.
Moreover, water moves inside and around the cell by osmotic pressure within each compartment and pulls fluid from one area to the other. The level of osmotic pressure remains approximately the same in ICF and ECF. Osmotic pressure can also be defined as the attraction of water to
Osmosis is the passage of water molecules from a weaker solution to a stronger solution through a partially permeable membrane. A partially permeable membrane only allows small molecules to pass through, so the larger molecules remain in the solution they originated in. Solute molecule [IMAGE] [IMAGE] Water molecule [IMAGE] The water molecules move into the more concentrated solution. When water enters a plant cell it swells up. The water pushes against the cell wall and the cell eventually contains all that it can hold.