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High school biology
Course: High school biology > Unit 3
Lesson 4: Osmosis and tonicityOsmosis and tonicity review
Key terms
| Term | Meaning |
|---|---|
| Passive transport | Type of transport that does not require energy to occur |
| Osmosis | The net movement of water across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration |
| Tonicity | The ability of an extracellular solution to make water move into or out of a cell by osmosis |
Osmosis
Osmosis is a passive transport process during which water moves from areas where solutes are less concentrated to areas where they are more concentrated.
Tonicity and cells
| Tonicity of solution | Solute concentration | Water moves... |
|---|---|---|
| Hypertonic | Higher solute in solution than in cell | Out of the cell |
| Isotonic | Equal amounts of solute in cell and solution | Into and out of cell at the same time |
| Hypotonic | Lower solute in solution than in cell | Into the cell |
Common mistakes and misconceptions
- In osmosis, water moves from areas of low concentration of solute to areas of high concentration of solute. But wait! Didn’t we say that osmosis is a passive process? It is! Water does still follow its concentration gradient, so it might be easier to think that water moves from where the concentration of water is high to where the concentration of water is low rather than thinking about solute concentration.
- Hypertonic and hypotonic are not the same. If a cell is put into a hypertonic solution, water will leave the cell. A quick tip to remembering this is to visualize “hyper” kids who want to go play outside! In contrast, when a cell is put into a hypotonic solution, water will enter the cell. Another trick to remembering this is that the cell swells and gets round like the “o” in hypo!
Want to join the conversation?
So dose Osmoses move in an area of Low to high concentaration?(5 votes)
depends what you mean by concentration, if you are talking about solute, then yes. But remember, it is the movement of water particles/molecules. Also, most people tend to say that water molecules from an area of high water potential to an area of low water potential, but that is basically the same as you say... low concentration of solute (e.g. salt) to high(6 votes)
doesn't water move from high concentrated water to low concentrated water(16 votes)- yes, so when the concentration of a solute is high, the concentration of water is lowered since there is more solute per water, less water per solute. Thus, when water moves from low concentrations of solute to high concentrations of solute, it moves from high concentrations of water to low concentrations of water.(25 votes)
I am confused- how can Osmosis be a form of Passive Transport if water moves from areas where solutes are less concentrated to areas where they are more concentrated. I though passive transport is when molecules move from areas of high concentration to low concentration, so shouldn't Osmosis technically be classified as a form of active transport? I don't fully understand the explanation given here, since it looks a bit unclear.(10 votes)
Hi,
Active transport is a process that uses energy from respiration.
Diffusion and osmosis don't require the cell to expend any of its own energy, as they are passive processes.
Diffusion is the spreading out of particles in a gas or solution resulting in the net movement of these particles from an area of higher concentration to an area of lower concentration
Osmosis is the movement of water particles from a dilute solution to a more concentrated solution through a selectively permeable membrane
As we know both are passive processes and yet (in basic, short terms) diffusion is higher to lower and osmosis is lower to higher, so movement to concentration doesn't determine whether it is active or passive.
Hope this helps!
Franek Mierzejewski(21 votes)
"In osmosis, water moves from areas of low concentration of solute to areas of high concentration of solute."
Does this mean that in osmosis water ONLY moves from areas of low concentration of solute to areas of high concentration of solute? Or just that it can?
thanks in advance :)(7 votes)
So osmosis only occurs with a semipermeable membrane, and even with the membrane some water will move both sides. MORE water will move up the concentration gradient, thus there is a net flow up the gradient.(12 votes)
- Why does the water diffuse into the glucose cell that is semi-permeable? I thought it goes from a high concentration to a low concentration and doesn't glucose have a higher concentration than water?(4 votes)
You could think of it like there's a higher concentration of water outside the cell / more of the outside solution's made of water than the one with the glucose.(5 votes)
Can someone please explain the difference between wall pressure,turgor pressure,osmotic pressure because its really confusing though its not in the video.thanks(6 votes)- Can anyone explain why Osmosis is a passive transport (its an area of lower solute concentration to an area of higher solute concentration). In the previous video, Sal discussed that the movement of a higher concentration to lower concentration is a passive transport. I'm confused "((3 votes)
- Water follows its concentration gradient, meaning that it will move from a higher concentration of water to a lower concentration of water. Instead of thinking about it in terms of solute, think about it in terms of water concentration. A low concentration of solute to a high concentration of solute means high water concentration to low water concentration.(5 votes)
Heres a tip: Hypo = Net Inflow.(4 votes)- Are you able to explain hypotonic, hypertonic when talking about isotonic solutions? For example, if 5%DW is isotonic, does that mean 3%DW is hypotonic?(4 votes)
- In my notes, it says osmosis is from hypo to hyper and that diffusion is hyper to hypo.
But this video only looks at when water is moving. I am having a hard time understanding how these two situations play out(3 votes)- hi
Diffusion is the movement of molecules( of any kind )from a region of high concentration to a region of low concentration.On the other hand osmosis deals with water,purely.we could define osmosis as the movement of water molecules from a region of high water concentration to region of low water concentration,which is basically from hypo to hyper,because if there is more water/high water concentration the solution is hypotonic.I hope i have helped you in a way.(2 votes)
