1. Watch these Videos
1.a. Osmosis
1.b. Water Potential
1.c. Osmosis Rap
2. Study this Summary
Osmosis
- Definition of Osmosis:
- Osmosis is the diffusion of water from higher to lower concentration.
- Water moves from a hypotonic (more water, less solute) solution to a hypertonic (less water, more solute) solution.
- Key Concepts of Osmosis:
- Hypotonic: More water, less solute relative to another solution.
- Hypertonic: Less water, more solute relative to another solution.
- Isotonic: Equal water and solute concentrations on both sides of the membrane.
- Applications:
- Gummy Bear Experiment: Water flows into the gummy bear (hypertonic to the surrounding water), causing it to expand due to osmotic pressure.
- Osmosis in Plant Cells:
- Plant Cell in a hypertonic environment: Water leaves the cell, causing plasmolysis and wilting.
- Plasmolysis is when the membrane of a plant cell moves away from the cell wall.
- Plant Cell in an isotonic environment: Water enters and leaves the cell at the same rate.
- Plant Cell in a hypotonic environment: Water flows into the cell, causing turgor pressure, making the plant firm and healthy.
- Plant Cell in a hypertonic environment: Water leaves the cell, causing plasmolysis and wilting.
- Osmosis in Animal Cells:
- Animal Cell in a hypertonic environment: Water leaves the cell, and the cell shrivels.
- Animal Cell in an isotonic environment: Water enters and leaves at the same rate, ideal for animal cells that are growing in cell culture.
- Animal Cell in a hypotonic environment: Water flows in, and the cell may burst due osmotic pressure.
- Contractile Vacuole in Freshwater Protists (unicellular eukaryotes)
- Protists are hypertonic to freshwater, causing water to flow into the cell.
- The contractile vacuole expels excess water to maintain osmotic balance (osmoregulation).
- Leaf Stomata:
- Stomata are pores on the underside of leaves formed by two guard cells.
- When water is abundant, guard cells swell and open the stomata, allowing gas exchange and water vapor release.
- Stomata close under water stress to conserve water.
- Regulation of Guard Cells:
- Water availability triggers adjacent cells to pump potassium ions into guard cells, making them hypertonic.
- Water follows by osmosis, causing the guard cells to buckle and open stomata.
- Under water scarcity, potassium ions exit guard cells, water follows, and stomata close.
Water Potential
- Definition and Symbol: Water potential (Ψ) measures the movement of water from areas of higher potential to lower potential.
- Water Potential Formula
- Ψ = Ψs + Ψp
- Ψs (solute potential): Adding solute decreases water potential.
- Ψp (pressure potential): Adding pressure (e.g., pressing a syringe) increases water potential.
- Examples
- U-Tube Example
- A U-tube with a semipermeable membrane separates two solutions.
- Adding solute (such as sucrose) to one side lowers its water potential. In the example in the video, on the side with added sugar Ψ = -0.23 MPa. The other side (without sugar) remains at Ψ = 0.
- Water moves from the side with higher potential (Ψ = 0) to lower potential (Ψ = -0.23 MPa).
- Potato Cell in Water
- A potato cell with Ψs = -1.0 MPa is placed in pure water (Ψ = 0).
- Water moves into the cell, causing it to expand. Expansion will continue until the pressure potential inside the cells equals the solute potential.
- U-Tube Example
3. Master these Flashcards
[qdeck bold_text=false qrecord_id=”sciencemusicvideosMeister1961-Osmosis and Water Potential Flashcards, APBVP”]
[h]Osmosis and Water Potential
[i]
[q]Define osmosis.
[a]Osmosis is the diffusion of water.
[q]Using two imaginary solutions, “A” and “B,” define hypotonic 1) in terms of dissolved solute, and 2) in terms of water concentration.
[a]In terms of dissolved solute: if solution “A” has less dissolved solute than solution “B,” then solution “A” is hypotonic to solution “B.”
In terms of water concentration: If solution “A” has a higher water concentration than solution “B,” then solution “A” is hypotonic to solution “B.”
[q]Using two imaginary solutions, “A” and “B,” define hypertonic 1) in terms of dissolved solute, and 2 in terms of water concentration.
[a]In terms of dissolved solute, if solution “A” has more dissolved solute than solution “B,” then solution “A” is hypertonic to solution “B.”
In terms of water concentration, if solution “A” has a lower water concentration than solution “B,” then solution “A” is hypertonic to solution “B.”
[q]Using two imaginary solutions, “A” and “B,” define isotonic 1) in terms of dissolved solute, and 2) in terms of water concentration.
[a]In terms of dissolved solute: If solution “A” has the same amount of dissolved solute as solution “B,” then solution “A” is isotonic to solution “B.”
In terms of water concentration: if solution “A” has the same water concentration as solution “B,” then solution “A” is isotonic to solution “B.”
[q]Using the terms hypotonic and hypertonic, describe how water flows.
[a]Water always flows from hypotonic to hypertonic.
[q json=”true” yy=”4″ dataset_id=”AP_Bio_Flashcards_2022|1dc1ce5e25910″ question_number=”71″ unit=”2.Cell_Structure_and_Function” topic=”2.8.Tonicity_and_Osmoregulation”] Explain the function of the contractile vacuole in freshwater protists such as Paramecia.
[a] Protists in freshwater are hypertonic to their freshwater environment. As a result, water moves into these cells by osmosis. To osmoregulate, many protists contain an organelle called a contractile vacuole. This organelle fills with water and then contracts to expel water from the cell. If the environment becomes more hypertonic (diminishing the water potential gradient) the cell can adapt by decreasing its rate of contractile vacuole contraction, and do the reverse in more hypotonic environments.
[q json=”true” yy=”4″ dataset_id=”AP_Bio_Flashcards_2022|1db75428a3910″ question_number=”72″ unit=”2.Cell_Structure_and_Function” topic=”2.8.Tonicity_and_Osmoregulation”] Explain how the central vacuole in a plant cell responds to changes in a plant’s environment.
[a] As water moves into a plant, following a water potential gradient, water will enter cells and move into a plant cell’s central vacuole. As the vacuole fills with water it expands, pushing against the plant cell wall. This outward pressure is called turgor, and it keeps plants full and firm (imagine a crispy lettuce leaf). If plants are low on water, the force of turgor diminishes, and plants wilt in response.
[q json=”true” yy=”4″ dataset_id=”AP_Bio_Flashcards_2022|1db75428a3910″ question_number=”73″ unit=”2.Cell_Structure_and_Function” topic=”2.8.Tonicity_and_Osmoregulation”] Use the principles of osmosis to explain each of the images below.
[a] The cell on the left is in an environment that’s hypertonic to the cell. Water leaves the cell, causing the membrane to peel away from the wall, a condition called plasmolysis. The plant as a whole will wilt. The cell in the center is in an environment that’s isotonic to the cell: water enters and leaves the cell at the same rate. The cell on the right is in a hypotonic environment. Water is flowing from the hypotonic environment into the cells. The pressure created as the membrane pushes against the wall is called turgor pressure (healthy condition for the plant).
[q json=”true” yy=”4″ unit=”2.Cell_Structure_and_Function” dataset_id=”AP_Bio_Flashcards_2022|1dac44f028910″ question_number=”74″ topic=”2.8.Tonicity_and_Osmoregulation”] Explain what happens to a cell in a hypotonic environment.
[a] If a cell is in a hypotonic environment, that means that the solution that the cell is in has less solute and more water than does the interior of the cell. Because water always flows from hypotonic (where the water is more concentrated) to hypertonic, water will flow from the hypotonic solution into the cell.
[q json=”true” yy=”4″ unit=”2.Cell_Structure_and_Function” topic=”2.8.Tonicity_and_Osmoregulation” dataset_id=”AP_Bio_Flashcards_2022|207799c9b066fd” question_number=”75″] Explain what happens to a cell in a hypertonic environment.
[a] When in a hypertonic environment, the solution outside the cell has relatively less water and more solute than the cell does. Because the cell is hypotonic to its environment, water will flow from the cell to its environment. The cell loses water.
[q json=”true” yy=”4″ unit=”2.Cell_Structure_and_Function” topic=”2.8.Tonicity_and_Osmoregulation” dataset_id=”AP_Bio_Flashcards_2022|2076dd31ed42fd” question_number=”76″] Explain what happens to a cell in an isotonic environment.
[a] A cell in an isotonic solution has the same concentration of solutes and water as the solution that it’s in. Water will flow into and out of the cell at the same rate, so it neither gains nor loses water.
[q json=”true” yy=”4″ unit=”2.Cell_Structure_and_Function” topic=”2.8.Tonicity_and_Osmoregulation” dataset_id=”AP_Bio_Flashcards_2022|2075e66500dafd” question_number=”77″] Compare the consequences of being in a hypotonic environment for animal and plant cells.
[a] An animal cell in a hypotonic environment will take up water as the water flows from the hypotonic environment into the cell. The cell will expand, and eventually burst.
A plant cell in a hypotonic environment will take up water as the water flows into the cell. The cell will expand, but its expansion will be limited by the cell’s rigid cell wall. The cell will become turgid, which is a healthy condition for a plant cell.
[q json=”true” yy=”4″ unit=”2.Cell_Structure_and_Function” topic=”2.8.Tonicity_and_Osmoregulation” dataset_id=”AP_Bio_Flashcards_2022|207506e08b5afd” question_number=”78″] Compare the consequences of being in a hypertonic environment for animal and plant cells.
[a] In a hypertonic environment, an animal cell will shrink and shrivel as it loses water. In a hypertonic environment, water will flow out of a plant cell. This will pull the membrane away from the cell wall. The lack of pressure will cause the plant itself to wilt.
[q json=”true” yy=”4″ unit=”2.Cell_Structure_and_Function” dataset_id=”AP_Bio_Flashcards_2022|1d8cd64fa2910″ question_number=”79″ topic=”2.8.Tonicity_and_Osmoregulation”] Describe the structure of leaf stomata.
[a] Stomata (at right) are pores on the underside of leaves Each stoma (singular) is formed by two guard cells. These cells, when they have sufficient water, buckle outward, creating a pore that allows carbon dioxide to enter the leaf for photosynthesis, but which also allows water vapor to escape. Stomata close in response to environmental cues, including water stress (a topic covered in another card).
[q json=”true” yy=”4″ unit=”2.Cell_Structure_and_Function” topic=”2.8.Tonicity_and_Osmoregulation” dataset_id=”AP_Bio_Flashcards_2022|2072fb0217f6fd” question_number=”80″] Explain how guard cells are regulated in order to open and close stomata.
[a] When water is available, cells adjacent to the stomata pump potassium ions into the guard cells. Water follows by osmosis, causing the guard cells to buckle and open. When water is scarce, this pumping stops. Potassium ions flow out of the guard cells, and water follows, causing the stomata to close.
[q json=”true” yy=”4″ unit=”2.Cell_Structure_and_Function” dataset_id=”AP_Bio_Flashcards_2022|1d5c611829510″ question_number=”82″ topic=”2.8.Tonicity_and_Osmoregulation”] What is water potential?
[a] Water potential is a measurement of water’s tendency to move from where it is to where it’s not, as determined by variables such as solute concentration and pressure. The basic idea is that water will always flow from areas of higher water potential to areas of lower water potential.
[q json=”true” yy=”4″ unit=”2.Cell_Structure_and_Function” dataset_id=”AP_Bio_Flashcards_2022|1d520c2365910″ question_number=”83″ topic=”2.8.Tonicity_and_Osmoregulation”] Explain the formula for water potential: Ψ = ΨS + ΨP (water potential = solute potential + pressure potential).
[a] In the formula Ψ = ΨS + ΨP ,
- Ψ represents water potential: water’s tendency to flow from where it is to where it’s not, based on a few other variables.
- ΨS is solute potential. Adding solute to water decreases its water potential. If that body of water is adjacent to an area with higher water potential, then the water will flow from the area with higher water potential (with less solute) to the area with the lower potential (with more solute). This is exactly like how water will flow from a hypotonic area to a hypertonic area.
- Ψp is pressure potential. Adding pressure (like pressing on the plunger in a syringe) increases water potential, causing water to flow away from that higher pressure area toward an area with lower pressure (and lower water potential).
[q json=”true” yy=”4″ dataset_id=”AP_Bio_Flashcards_2022|additional1″ question_number=”84″ unit=”2.Cell_Structure_and_Function” topic=”2.8.Tonicity_and_Osmoregulation”] Explain osmosis in terms of water potential?
[a] Osmosis is the movement of water across a semipermeable membrane from areas of higher water potential to areas of lower water potential. Water potential quantifies this movement shows the influence of factors such as solute concentration (solute potential) and physical pressure (pressure potential).
[q json=”true” yy=”4″ dataset_id=”AP_Bio_Flashcards_2022|additional2″ question_number=”85″ unit=”2.Cell_Structure_and_Function” topic=”2.8.Tonicity_and_Osmoregulation”] How does adding solute affect water potential?
[a] Adding solute to a solution decreases its water potential because solute molecules attract water. This reduces the free energy of the water and its tendency to move to other areas. Note: the free energy part of this explanation is outside the scope of AP Bio
[q json=”true” yy=”4″ dataset_id=”AP_Bio_Flashcards_2022|additional3″ question_number=”86″ unit=”2.Cell_Structure_and_Function” topic=”2.8.Tonicity_and_Osmoregulation”] How does pressure influence water potential?
[a] Adding pressure to a solution increases its water potential. For example, applying pressure to a syringe filled with water forces water to flow to areas with lower pressure potential.
[q json=”true” yy=”4″ dataset_id=”AP_Bio_Flashcards_2022|additional5″ question_number=”88″ unit=”2.Cell_Structure_and_Function” topic=”2.8.Tonicity_and_Osmoregulation”] How does water potential explain turgor pressure in plant cells?
[a] In a hypotonic environment, water flows into plant cells due to higher water potential outside the cell compared to inside. This causes the central vacuole to fill, and the cell membrane pushes against the rigid cell wall, creating turgor pressure. This pressure helps maintain the plant’s structure.
[x][restart]
[/qdeck]
4. Tackle these Quizzes
4.1. Osmosis
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[h]Osmosis
[i]This quiz tests you on your understanding of osmosis, and your ability to explain phenomena like the one below.
[q]A solution that has a higher solute concentration than a solution on the other side of the membrane is ___________
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[q]A solution that has a higher water concentration than a solution on the other side of the membrane is ___________
[c]aHlwb3 Rvbmlj[Qq]
[c]aHlwZXJ0b25pYw==[Qq]
[c]aXNvdG9uaWM=[Qq]
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Cg==[Qq]
[q]A solution that has the same solute concentration as a solution on the other side of the membrane is ___________
[c]aHlwb3Rvbmlj[Qq]
[c]aHlwZXJ0b25pYw==[Qq]
[c]aXNvdG 9uaWM=[Qq]
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Cg==[Qq]
[q]A solution that has a lower solute concentration than a solution on the other side of the membrane is ___________
[c]aHlwb3 Rvbmlj[Qq]
[c]aHlwZXJ0b25pYw==[Qq]
[c]aXNvdG9uaWM=[Qq]
[f]WWVzLiA=SHlwb3RvbmljIG1lYW5zICYjODIyMDtsZXNzIHNvbHV0ZS4mIzgyMjE7[Qq]
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[Qq][q]A solution that has a lower water concentration than a solution on the other side of the membrane is ___________
[c]aHlwb3Rvbmlj[Qq]
[c]aHlwZXJ0 b25pYw==[Qq]
[c]aXNvdG9uaWM=[Qq]
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Cg==[Qq]
[q]A solution that has the same water concentration as a solution on the other side of the membrane is ___________
[c]aHlwb3Rvbmlj[Qq]
[c]aHlwZXJ0b25pYw==[Qq]
[c]aXNvdG 9uaWM=[Qq]
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Cg==[Qq]
[q]A gummy bear is placed in water. The gummy bear is made mostly of sugar, held together by gelatin. The gummy bear is ___________ to the water.
[c]aHlwb3Rvbmlj[Qq]
[c]aHlwZXJ0 b25pYw==[Qq]
[c]aXNvdG9uaWM=[Qq]
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[f]RXhjZWxsZW50LsKgQSBndW1teSBiZWFyLCB3aXRoIGFsbCBvZiBpdHMgc3VnYXIswqBoYXMgYSBoaWdoZXIgc29sdXRlIGNvbmNlbnRyYXRpb24gdGhhbiB0aGUgd2F0ZXIgdGhhdCBpdCYjODIxNztzIGluLiDCoFRoYXQgbWFrZXMgdGhlIGd1bW15wqA=aHlwZXJ0b25pYw==IHRvIHRoZSB3YXRlci4=[Qq]
[f]Tm8uIA==SXNvdG9uaWM=IG1lYW5zICYjODIyMDt0aGUgc2FtZSBhbW91bnQgb2Ygc29sdXRlLiYjODIyMTsgWW91JiM4MjE3O3JlIGNvbXBhcmluZyBhIGd1bW15IGJlYXIsIHdpdGggYWxsIG9mIGl0cyBzdWdhciwgdG8gbW9zdGx5IHB1cmUgd2F0ZXIuIFdoYXQgd29yZCBtZWFucyAmIzgyMjA7bW9yZSBzb2x1dGU/JiM4MjIxOw==
Cg==[Qq]
[q]In this diagram, the cell is ________ to the solution outside the cell
[c]aHlwb3Rvbmlj[Qq]
[c]aHlwZXJ0 b25pYw==[Qq]
[c]aXNvdG9uaWM=[Qq]
[f]Tm8uIA==SHlwb3RvbmljIG1lYW5zICYjODIyMDtsZXNzIHNvbHV0ZS4mIzgyMjE7IExvb2sgYXQgaG93IG11Y2ggbW9yZSBzb2x1dGUgaXMgaW5zaWRlIHRoZSBjZWxsIHRoYW4gb3V0c2lkZS4gV2hhdCB0ZXJtIG1lYW5zICYjODIyMDtoaWdoZXIgc29sdXRlIGNvbmNlbnRyYXRpb24/JiM4MjIxOw==[Qq]
[f]WWVzLiBIeXBlcnRvbmljIG1lYW5zIGhpZ2hlciA=c29sdXRlIGNvbmNlbnRyYXRpb24uIEFzIHlvdSBjYW4gc2VlLCB0aGUgY2VsbCBpcyBoeXBlcnRvbmljIHRvIGl0cyBlbnZpcm9ubWVudC4=[Qq]
[f]Tm8uIA==SXNvdG9uaWM=IG1lYW5zICYjODIyMDtzYW1lIHNvbHV0ZSAob3Igd2F0ZXIpIGNvbmNlbnRyYXRpb24uJiM4MjIxO8KgTG9vayBhdCBob3cgbXVjaCBtb3JlIHNvbHV0ZSBpcyBpbnNpZGUgdGhlIGNlbGwgdGhhbiBvdXRzaWRlLiBXaGF0IHRlcm0gbWVhbnMgJiM4MjIwO2hpZ2hlciBzb2x1dGUgY29uY2VudHJhdGlvbj8mIzgyMjE7
Cg==[Qq]
[q]In this diagram, the cell is ________ to the solution outside the cell
[c]aHlwb3 Rvbmlj[Qq]
[c]aHlwZXJ0b25pYw==[Qq]
[c]aXNvdG9uaWM=[Qq]
[f]WWVzLiA=SHlwb3RvbmljIG1lYW5zICYjODIyMDtsZXNzIHNvbHV0ZS4mIzgyMjE7IEFzIHlvdSBjYW4gc2VlLCB0aGUgY2VsbCBpcyBoeXBvdG9uaWMgdG8gaXRzIGVudmlyb25tZW50Lg==[Qq]
[f]Tm8uIEh5cGVydG9uaWMgbWVhbnMgaGlnaGVyIA==c29sdXRlIGNvbmNlbnRyYXRpb24uIEp1c3QgYnkgbG9va2luZywgeW91IGNhbiB0ZWxsIHRoYXQgdGhlcmUmIzgyMTc7cyBhIGxvd2VyIGNvbmNlbnRyYXRpb24gb2Ygc29sdXRlIGluc2lkZSB0aGUgY2VsbCB0aGFuIG91dHNpZGUgdGhlIGNlbGwuIMKgV2hhdCB0ZXJtIG1lYW5zICYjODIyMDtsb3dlciBzb2x1dGUgY29uY2VudHJhdGlvbj8mIzgyMjE7[Qq]
[f]Tm8uIA==SXNvdG9uaWM=IG1lYW5zICYjODIyMDtzYW1lIHNvbHV0ZSAob3Igd2F0ZXIpIGNvbmNlbnRyYXRpb24uJiM4MjIxO8KgSnVzdCBieSBsb29raW5nLCB5b3UgY2FuIHRlbGwgdGhhdCB0aGVyZSYjODIxNztzIGEgbG93ZXIgY29uY2VudHJhdGlvbiBvZiBzb2x1dGUgaW5zaWRlIHRoZSBjZWxsIHRoYW4gb3V0c2lkZSB0aGUgY2VsbC4gwqBXaGF0IHRlcm0gbWVhbnMgJiM4MjIwO2xvd2VyIHNvbHV0ZSBjb25jZW50cmF0aW9uPyYjODIyMTs=
Cg==[Qq]
[q]In this situation, water will
[c]ZmxvdyBpbnRvIH RoZSBjZWxsLg==[Qq]
[c]ZmxvdyBvdXQgb2YgdGhlIGNlbGw=[Qq]
[c]ZmxvdyBpbnRvIGFuZCBvdXQgb2YgdGhlIGNlbGwgYXQgZXF1YWwgcmF0ZXMsIHdpdGggbm8gbmV0IGNoYW5nZS4=[Qq]
[f]WWVzLiBXYXRlciBhbHdheXMgZmxvd3MgZnJvbSBoeXBvdG9uaWMgdG8gaHlwZXJ0b25pYy7CoEJlY2F1c2UgdGhlIGNlbGwgaXMgaHlwZXJ0b25pYyB0byBpdHMgZW52aXJvbm1lbnQsIHdhdGVyIHdpbGwgZmxvdyA=aW50bw==IHRoZSBjZWxsLg==[Qq]
[f]Tm8uIFdhdGVyIGFsd2F5cyBmbG93cyBmcm9tIGh5cG90b25pYyB0byBoeXBlcnRvbmljLiBJcyB0aGlzIGNlbGwgaHlwZXJ0b25pYyBvciBoeXBvdG9uaWMgdG8gaXRzIGVudmlyb25tZW50Pw==[Qq]
[f]Tm8uIFdhdGVyIGZsb3cgd291bGQgYmUgZXF1YWwgaWYgdGhlIGNlbGwgd2VyZSBpc290b25pYyB0byBpdHMgZW52aXJvbm1lbnQsIGFuZCB0aGF0JiM4MjE3O3Mgbm90IHRoZSBjYXNlLiBLZWVwIGluIG1pbmQgdGhhdCB3YXRlciBhbHdheXMgZmxvd3MgZnJvbSBoeXBvdG9uaWMgdG8gaHlwZXJ0b25pYywgYW5kIGZpZ3VyZSBvdXQgdGhlIGFuc3dlci4=
Cg==[Qq]
[q]In this situation, water will
[c]ZmxvdyBpbnRvIHRoZSBjZWxsLg==[Qq]
[c]ZmxvdyBvdXQgb2 YgdGhlIGNlbGw=[Qq]
[c]ZmxvdyBpbnRvIGFuZCBvdXQgb2YgdGhlIGNlbGwgYXQgZXF1YWwgcmF0ZXMsIHdpdGggbm8gbmV0IGNoYW5nZS4=[Qq]
[f]Tm8uIFdhdGVyIGFsd2F5cyBmbG93cyBmcm9tIGh5cG90b25pYyB0byBoeXBlcnRvbmljLiBUaGUgaHlwb3RvbmljIHNpZGUgaXMgdGhlIG9uZSB3aXRoIGxlc3Mgc29sdXRlLiBOb3cgZmlndXJlIG91dCB0aGUgYW5zd2VyLg==[Qq]
[f]WWVzLiBXYXRlciBhbHdheXMgZmxvd3MgZnJvbSBoeXBvdG9uaWMgdG8gaHlwZXJ0b25pYy4gQmVjYXVzZSB0aGUgY2VsbCBpcyBoeXBvdG9uaWMgdG8gaXRzIGVudmlyb25tZW50LCB3YXRlciB3aWxsIGZsb3cgb3V0IG9mwqB0aGUgY2VsbC4=[Qq]
[f]Tm8uIFdhdGVyIGZsb3cgd291bGQgYmUgZXF1YWwgaWYgdGhlIGNlbGwgd2VyZSBpc290b25pYyB0byBpdHMgZW52aXJvbm1lbnQsIGFuZCB0aGF0JiM4MjE3O3Mgbm90IHRoZSBjYXNlLiBLZWVwIGluIG1pbmQgdGhhdCB3YXRlciBhbHdheXMgZmxvd3MgZnJvbSBoeXBvdG9uaWMgdG8gaHlwZXJ0b25pYywgYW5kIGZpZ3VyZSBvdXQgdGhlIGFuc3dlci4=
Cg==[Qq]
[q]Assume that this cell is an animal cell (without a cell wall). In this situation, the cell will
[c]aW5jcmVhc2Ug aW4gc2l6ZQ==[Qq]
[c]ZGVjcmVhc2UgaW4gc2l6ZQ==[Qq]
[c]cmVtYWluIHRoZSBzYW1lIHNpemUu[Qq]
[f]WWVzLiBXYXRlciBhbHdheXMgZmxvd3MgZnJvbSBoeXBvdG9uaWMgdG8gaHlwZXJ0b25pYy7CoEFzIHdhdGVyIGZsb3dzIGludG8gdGhlIGh5cGVydG9uaWMgY2VsbCwgaXQgd2lsbCBpbmNyZWFzZSBpbiBzaXplLg==[Qq]
[f]Tm8uIFdhdGVyIGFsd2F5cyBmbG93cyBmcm9tIGh5cG90b25pYyB0byBoeXBlcnRvbmljLiBJcyB0aGlzIGNlbGwgaHlwZXJ0b25pYyBvciBoeXBvdG9uaWMgdG8gaXRzIGVudmlyb25tZW50PyBGaWd1cmUgdGhhdCBvdXQsIHRoZW4gZmlndXJlIG91dCB0aGUgZGlyZWN0aW9uIG9mIHdhdGVyIGZsb3cu[Qq]
[f]Tm8uIFRoZSBjZWxsIHdvdWxkIHN0YXkgdGhlIHNhbWUgc2l6ZSBpZiBpdCB3ZXJlIGlzb3RvbmljIHRvIGl0cyBlbnZpcm9ubWVudC4gSXQmIzgyMTc7cyBub3QuIEtlZXAgaW4gbWluZCB0aGF0IHdhdGVyIGFsd2F5cyBmbG93cyBmcm9tIGh5cG90b25pYyB0byBoeXBlcnRvbmljLCBhbmQgZmlndXJlIG91dCB0aGUgYW5zd2VyLg==
Cg==[Qq]
[q]Assume that this cell is an animal cell (without a cell wall). In this situation, the cell will
[c]aW5jcmVhc2UgaW4gc2l6ZQ==[Qq]
[c]ZGVjcmVhc2Ug aW4gc2l6ZQ==[Qq]
[c]cmVtYWluIHRoZSBzYW1lIHNpemUu[Qq]
[f]Tm8uIFdhdGVyIGFsd2F5cyBmbG93cyBmcm9tIGh5cG90b25pYyB0byBoeXBlcnRvbmljLiBJcyB0aGlzIGNlbGwgaHlwZXJ0b25pYyBvciBoeXBvdG9uaWMgdG8gaXRzIGVudmlyb25tZW50PyBGaWd1cmUgdGhhdCBvdXQsIHRoZW4gZmlndXJlIG91dCB0aGUgZGlyZWN0aW9uIG9mIHdhdGVyIGZsb3cu[Qq]
[f]WWVzLiBXYXRlciBhbHdheXMgZmxvd3MgZnJvbSBoeXBvdG9uaWMgdG8gaHlwZXJ0b25pYy7CoEFzIHdhdGVyIGZsb3dzIG91dCBvZsKgdGhlIGh5cG90b25pY8KgY2VsbCwgaXQgd2lsbCBkZWNyZWFzZcKgaW4gc2l6ZS4=[Qq]
[f]Tm8uIFRoZSBjZWxsIHdvdWxkIHN0YXkgdGhlIHNhbWUgc2l6ZSBpZiBpdCB3ZXJlIGlzb3RvbmljIHRvIGl0cyBlbnZpcm9ubWVudC4gSXQmIzgyMTc7cyBub3QuIEtlZXAgaW4gbWluZCB0aGF0IHdhdGVyIGFsd2F5cyBmbG93cyBmcm9tIGh5cG90b25pYyB0byBoeXBlcnRvbmljLCBhbmQgZmlndXJlIG91dCB0aGUgYW5zd2VyLg==
Cg==[Qq]
[q]When plant cells are in this environment, they’ll be the most solid and firm.
[c]aHlwb3 Rvbmlj[Qq]
[c]aHlwZXJ0b25pYw==[Qq]
[c]aXNvdG9uaWM=[Qq]
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Cg==[Qq]
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Cg==[Qq]
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Cg==Cg==[Qq]
[q]When animal cells are in this environment, they’ll shrink and shrivel
[c]aHlwb3Rvbmlj[Qq]
[c]aHlwZXJ0 b25pYw==[Qq]
[c]aXNvdG9uaWM=[Qq]
[f]Tm8uIFdoZW4gYW5pbWFsIGNlbGxzIGFyZSBpbiBhIGh5cG90b25pYyBlbnZpcm9ubWVudCwgd2F0ZXIgZmxvd3MgaW50byB0aGUgY2VsbHMuIFN0dWR5IHRoZSBkaWFncmFtIGJlbG93IHRvIHNlZSB3aGF0IGNvbmRpdGlvbnMgd2lsbCBjYXVzZSBhbmltYWwgY2VsbHMgdG8gc2hyaW5rIGFuZCBzaHJpdmVsLg==
Cg==[Qq]
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Cg==[Qq]
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Cg==Cg==[Qq]
[q]When a plant is in this environment, it wilts.
[c]aHlwb3Rvbmlj[Qq]
[c]aHlwZXJ0 b25pYw==[Qq]
[c]aXNvdG9uaWM=[Qq]
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Cg==[Qq]
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Cg==[Qq]
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Cg==Cg==[Qq]
[q]When animal cells are in this environment, they’ll expand, then burst.
[c]aHlwb3 Rvbmlj[Qq]
[c]aHlwZXJ0b25pYw==[Qq]
[c]aXNvdG9uaWM=[Qq]
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Cg==[Qq]
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Cg==Cg==[Qq]
[q]If you want to keep animal tissue or cells alive outside the body, you have to keep them in what kind of osmotic environment?
[c]aHlwb3Rvbmlj[Qq]
[c]aHlwZXJ0b25pYw==[Qq]
[c]aXNvdG 9uaWM=[Qq]
[f]Tm8uIFdoZW4gYW5pbWFsIGNlbGxzIGFyZSBpbiBhIGh5cG90b25pYyBlbnZpcm9ubWVudCwgd2F0ZXIgZmxvd3MgaW50byB0aGUgY2VsbHMuwqBUaGlzIGNhdXNlcyB0aGVtIHRvIGV4cGFuZCwgYW5kIGV2ZW50dWFsbHkgYnVyc3QuIFdoYXQgY29uZGl0aW9uIGtlZXBzIHRoZW0gdGhlIHNhbWUgc2l6ZSAod2hpY2ggaXMgdGhlIGhlYWx0aGllc3QgY29uZGl0aW9uIGZvciB0aGUgY2VsbHMpPw==
Cg==[Qq]
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Cg==[Qq]
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Cg==[Qq]
[x]
[restart]
[/qwiz]
4.2. Water Potential
[qwiz random=”false” style=”min-height: 350px !important;” qrecord_id=”sciencemusicvideosMeister1961-Water Potential Quiz, APBVP”]
[h]Water Potential
[i]
[q multiple_choice=”true”] In the scenario illustrated below, the membrane is permeable to water, but not to the solute (sucrose). If you pour sugar into the left side of U-tube 2, what will happen?
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[q] Tube 3 shows what happens if you add solute to the left side of the U-tube. In terms of water potential, what happened is that the water potential on the right side of the tube is now [hangman] than the water potential on the left side of the tube. That’s because adding solute [hangman] water potential.
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[q] You should note that while the concept of water potential might be new, the scenario below can be explained just in terms of osmosis. Osmosis is the [hangman] of water. Adding solute made the left side [hangman] to the right side, and water always flows from [hangman] to hypertonic.
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[q labels = “top”]Quantifying what happens when you add solute to one side of a U-tube is pretty straightforward. The pure water on the right side is not under pressure, and it has no dissolved solutes. Therefore its water potential will be 0 MPa. Start by dragging its water potential next to its Ψ symbol. There’s also no pressure on the solution on the left side, so you can drag the correct number to the Ψp (pressure potential) symbol on the left. Adding solute has lowered the solute potential of the left side, so drag the appropriate number to the Ψs symbol on the left, and then total everything up.
[l]0 MPa
[fx] No, that’s not correct. Please try again.
[f*] Great!
[l]-0.23 MPa
[fx] No, that’s not correct. Please try again.
[f*] Good!
[q]Pressure is another component of water potential. Imagine that you took a plunger and used it to press down on the left side of the U-tube, as shown in “2.” Predict what will happen, and why.
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[q]The downward force of the plunger increases the [hangman] potential on the left side. Because the formula for water potential, is Ψtotal = Ψs + Ψp, we know that increasing Ψp will increase the overall [hangman] potential. Because water always flows from [hangman] to [hangman] water potential, it moves from the left side to the right side.
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[q]If you place a flaccid cell in pure water (Ψ = 0.0 MPa, as shown below), what will happen to the cell? Note that in this scenario, the cytoplasm has a Ψs of -1.0 MPa.
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[q]Beaker number 2 shows what will happen to beaker number 1 over time. Because the water in the beaker has a water potential of [hangman] MPa, water will flow from the beaker, where the water potential is [hangman], into the cell. What’s lowering the cell’s water potential is the [hangman] in the cytoplasm. In beaker 2, the [hangman] potential, which has risen to 1.0 MPa, is counteracting the -1.0 MPa [hangman] potential, so the cell’s shape has changed.
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[x]
[/qwiz]
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This topic ends Unit 2 of AP Bio (Cell Structure and Function)
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