Osmosis is the net movement of solvent across a semipermeable membrane.
Understanding Osmosis
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Osmosis Concept 1
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Osmosis is the net movement of a solvent, usually water, across a semipermeable membrane. Now, this semipermeable membrane is just the material that's allowing solvents and other small molecules to pass across and we're going to say that these cell membranes that are around living cells are in fact semipermeable themselves. Now, these cell membranes, they prevent solutes from passing through and these solutes can be ions or large molecules. Now, if we take a look here at this illustration of a semi permeable membrane, here the membrane is asking if you have an appointment. This larger molecule in red is trying to get through and they can't get past the barrier. But the smaller ones down here do have an appointment, are allowed to pass through because they are the right size, and they can pass through the semipermeable membrane to the other side. And this is the way that, semi permeable membranes work. Osmosis is the movement of water, net movement of water, but semi permeable membranes can halt and stop certain molecules from traversing from one side to the other side of a living cell.
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Osmosis Concept 2
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Alright, everyone. So at this point, we can say that the solvent moves from a lower concentration solution to a higher concentration solution. And eventually, equilibrium is reached and the net flow of solvent is stopped by osmotic pressure. Now, what exactly is osmotic pressure itself? Well, it's the counter force required to stop the flow of solvent through the semi permeable membrane. So let's pretend that my hand is this semi permeable membrane. And we have the flow of water on this side is less concentrated. Over here, on the other side of the semi permeable membrane, it's more concentrated. Water is going to want to flow through this semi permeable membrane to the other side. Now, as water is flowing through, there's going to be some resistance. There is a pressure that's on this side of the semipermeable membrane. That pressure is osmotic pressure. So the solvent's passing through the semipermeable membrane, trying to go from the less concentrated solution to, to the more concentrated solution. But my osmotic pressure that's building behind here is trying to stop the flow of water or the flow of solvent. K. So that's what osmotic pressure is. It's the counterforce that's pushing against the sulfur that's coming through the semiperlable membrane. Now if we take a look here at this image, we have these little blue spheres which represent our solvent molecules. And then we have our solute molecules. If we take a look at our two images, we can see in the top part, we have how many solute particles. We have 1, 2, 3, 4, 5, 6, 7 of the solute particles. And then we only have 3 solvent. Then if we look at the bottom part, we have what? 2 solute. And we see that we have way more solvent a ton. So actually let's count. We have 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15. Right. So we have 15 solvent. We We didn't really need to count. We can already see there's way more solvent than solute. So we can say that the bottom part is the part that is less concentrated because there's way more of our solvents there. So it's it's the lower concentration solution. The top part has way more solute than solvent, so it's the more concentrated or higher concentration solution. So that means water is gonna flow naturally from the less the lower concentration side to the higher. So water is gonna move this way. As it's moving through this semiperbal membrane here, remember there's gonna be that force that's kind of trying to stop the flow of water. That's the osmotic pressure. It's building on this side here. Because remember, what's the ultimate goal of osmosis? The ultimate goal of osmosis is to get both sides to have the same equal solution concentrations. And we're gonna say the bigger the difference in solution concentrations on both sides, then the higher the osmotic pressure needed to stop the flow of solvent. Right? So that's what we'd say in terms of this particular image. If we go to the other side, what do we see? Well, if we go to the other side we have 1, 2, 3, 4, 5, 6, 7 solute. And then solvent, we have 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, which is basically a 1 to 2 ratio. One solute for every 2 solvent. If we look here, we have what? We have 2 solute and 4 solvent. The numbers are smaller, but if we are paying attention here, we can see if the ratio is still the same. It's still a 1 to 2 ratio. It's still a 1 solute for every 2 solvent. So although numbers look different, the ratios are the same. So the concentrations on both sides are the same. K. So we'd say that there is no net flow between the 2 because both sides already have equal con solution concentrations. Right. So here we wouldn't talk about the flow of solvent. Alright. So just remember, this is what we're talking about. Osmosis is the flow of water from a lower concentration or less concentrated side to a more concentrated side. And as it's passing through the semipermeable membrane, there's an osmotic pressure that's kind of trying to stop that flow of solvent.
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example
Osmosis Example 1
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Here, osmosis is best defined as the movement of so remember, osmose osmosis is the movement of a solvent across a semipermeable membrane. Our solvent typically is water, so it's a movement of water molecules. So that means b and c are out. And let's see. Across the semipermeable membrane into a region of low solute concentration. No. Not low. High. Because of that, a can't be the answer. Therefore, d is the correct one where water molecules move across the semibromebrium membrane into a region of high solute concentration. So here, option d would be the correct answer.
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Problem
Problem
A semipermeable membrane is placed between the following solutions.
Which solution will increase in volume?
A
Solution A:6.78% NaCl
B
Solution B:12.7% NaCl
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Problem
Problem
Four U tubes each have distilled water in the right arm, a solution in the left arm, and a semipermeable membrane between the arms. If the solute is LiF, which solution is most concentrated?
A
B
C
D
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Problem
Problem
Identify the direction of water flow between 2 solutions separates by semipermeable membrane, where are the solute particles.
A
water will flow from solution A to solution B due to higher osmotic pressure on the solution B.
B
water will flow from solution A to solution B due to lower osmotic pressure on solution B.
C
water will flow from solution B to solution A due to lower osmotic pressure on solution B.
D
water will flow from solution B to solution A due to lower osmotic pressure on solution A.
E
water will not flow because both solutions have the same osmotic pressures.
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concept
Osmosis Concept 3
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We know that osmosis is the movement of a solvent from an area of low concentration to an area of high concentration. Now, the direction of solvent flow depends on tonicity. Tonicity itself is just the relative concentration of solutes dissolved in the solutions. Now, when we take a look at the different types of solutions realize that we're looking at solute concentration and osmotic pressure relative to one another. If we take a look here we have our hypotonic solution, our isotonic solution, and our hypertonic solution. With a hypotonic solution, it has a lower solute concentration and lower osmotic pressure relative to bodily fluids. And when we talk about isotonic solutions, this is when 2 solutions have the same solute concentration and osmotic pressure. Now, an interesting piece of information is when we deal with intravenous solutions, they must be isotonic to bodily fluids such as blood, plasma, tissue cells, tissue fluids, etcetera. And then finally, we have hypertonic solutions which has a higher solute concentration and osmotic pressure relative to body fluids. Now, if we take a look here, we're going to talk about hypotonic, isotonic and hypertonic environments and look at them in reference to their solute concentrations outside the cell, osmotic pressure outside the cell and the effects they have on red blood cells. So when we're looking at hypotonic solutions, we're going to say they have lower solute concentration. We said isotonic they would have equal solute concentrations between, two things being compared to one another. Hypertonic would have higher solute concentration. Now, what about their osmotic pressure outside the cell? Well, lower solute concentration would result in lower osmotic pressure. Here, the equal amount of solute concentration would equate to an equal osmotic pressure. Higher solute concentration will result in higher osmotic pressure. What effect does this have on a biological system such as a red blood cell? Well, here we're going to say that we have a lower concentration on the outside, so that would mean that it's more concentrated within the red blood cell. So remember, osmosis moves to where it's higher in concentration. So water would enter the cell. This causes a process known as hemolysis. So basically the cell will swell up because all the water is going in there, and if too much water gets in there it can burst. Okay, so a cell will swell and then could burst. Next, we have an isotonic environment. So the concentration inside and outside the red blood cell are the same. So water enters and exits the cell at equal rates so there is no net movement of water. The same amount that goes in is the same amount that comes out. Finally, if we're in a hypertonic environment that means that it's more concentrated on the outside of the red blood cell, so water is going to exit the cell. If enough water exits the cell this causes cremation, so the cell will dehydrate and it shrivels. Now, how's the way for us to remember, these different types of situations? Well, here let's say we're looking at a hypotonic environment. So a hypotonic environment, hypo sounds close to hippo. Hippos drinks, a hippo drinks too much water and swells like a cell. So hippos will take in a huge amount of water because the environment is hypotonic and they could burst or swell. Hypertonic environment, so the outside is more concentrated than the red blood cell. So a hypertonic environment can be related to a hyperkid. The hyperkid playing outside gets dehydrated like a cell. So if your environment is hypertonic, you're gonna lose water out of your red blood cell. It's gonna exit the red blood cell and try to dilute the outside environment. So just keep these little memory tools to help you know the distinction between hypotonic versus hypertonic. Isotonic, we know everything is equal on the inside and out so there's no net movement of water.
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example
Osmosis Example 2
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Here it says label the tonicity of the solution outside the cell where the dot, the purple dot, are these solute particles. Right. So what we have to do is we have to look at how many dots we have on the outside, and compare it to the number of dots on the inside. In the first image, we can see that inside the cell is more concentrated. Outside the cell is less concentrated. It has less purple dots. Remember, we have to discuss what's what type of solution is on the outside. Since the outside is less concentrated, it is a hypotonic solution. For the second one, both the inside and the outside have 5 purple dots, so 5 solute molecules. They're equal inside and out. So this would have to be an isotonic solution. And then finally here we have the outside having more dots. So outside is more concentrated. Since the outside is more concentrated, this represents a hypertonic solution. So just remember, we're looking at what the solution is on the outside relative to what's inside a particular cell.
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Problem
Problem
If the fluid surrounding a patient's red blood cells is depleted in electrolytes, is crenation or hemolysis more likely to occur?
A
crenation
B
hemolysis
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Problem
Problem
A solution with the same osmotic pressure as the blood is