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Questions and Answers
Passive transport requires energy in the form of ATP.
False
Osmosis is the diffusion of water from an area of high solute concentration to an area of low solute concentration.
False
Facilitated diffusion involves the movement of molecules through protein channels without energy usage.
True
Diffusion will continue until equilibrium is achieved.
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The movement of O2 into cells and CO2 out of cells represents active transport.
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Hypertonic solutions have more solute and less water than the surrounding environment.
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In a hypotonic solution, plant cells face the risk of bursting due to excessive water intake.
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In isotonic conditions, animal cells do not experience an osmotic pressure difference with their surroundings.
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A cell in salt water will typically lose water and may face environmental stress as a result.
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Contractile vacuoles function to absorb excess water in cells exposed to hypotonic environments.
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Study Notes
Membrane Transport
- Movement of materials across a cell membrane.
Passive Transport
- Does not require energy (ATP).
- Movement of particles along a concentration gradient from an area of higher concentration to an area of lower concentration.
Diffusion
- Movement of particles from high to low concentration areas.
- Continues until equilibrium is achieved.
- Example: Movement of Oxygen ($O_2$) into cells and Carbon Dioxide ($CO_2$) out of cells.
Simple Diffusion
- Passive transport.
- No energy (ATP) needed.
- Example: Movement of Oxygen ($O_2$) into cells and Carbon Dioxide ($CO_2$) out of cells.
Facilitated Diffusion
- Diffusion through protein channels.
- Channels move specific molecules across the cell membrane.
- No energy (ATP) needed.
- Example: Glucose movement.
Osmosis
- Diffusion of water through a selectively permeable membrane from an area of high concentration of water to an area of low concentration of water.
- Water moves from an area of lower solute concentration to an area of higher solute concentration.
- Important for aquatic organisms and kidney function.
Hypertonic
- More solute, less water.
Hypotonic
- Less solute, more water.
Isotonic
- Equal solute, equal water.
Managing Water Balance: Hypotonic Solutions
- A cell in freshwater.
- High concentration of water around the cell.
- Problem: Cell gains water, swells, and can burst.
- Example: Paramecium
- Solution: Contractile vacuole pumps water out of the cell.
- Uses ATP.
- Plant cells become turgid (full).
- Cell walls protect from bursting.
Managing Water Balance: Hypertonic Solutions
- A cell in saltwater.
- Low concentration of water around the cell.
- Problem: Cell loses water and can die.
- Example: Shellfish
- Solution: Take up water or pump out salt.
- Plant cells experience plasmolysis (wilt) but can recover.
Managing Water Balance: Isotonic Solutions
- Animal cell immersed in a mild salt solution.
- No difference in concentration of water between the cell and the environment.
- Problem: None.
- No net movement of water.
- Cell in equilibrium.
- Volume of cell is stable.
- Example: Blood cells in blood plasma.
- Slightly salty IV solution in a hospital.
Aquaporins
- Water moves rapidly into and out of cells.
- Evidence of water channels.
- Protein channels allowing flow of water across the cell membrane.
Active Transport
- Uses energy (ATP) to move materials across a cell membrane against a concentration gradient.
- Protein "pump."
- Requires energy (ATP).
- Example: Sodium-Potassium pump.
Sodium-Potassium Pump
- Membrane transport proteins pump Sodium ($Na^+$) out of the cell and Potassium ($K^+$) into the cell against the concentration gradient.
- Uses ATP.
- Nerve cells must maintain a higher concentration of Sodium ($Na^+$) outside the cell and Potassium ($K^+$) inside the cell to function.
Getting Through The Cell Membrane
-
Passive Transport
- Simple diffusion: Nonpolar, hydrophobic molecules.
- Facilitated transport: Polar, hydrophilic molecules through a protein channel.
-
Active transport: Against concentration gradient.
- Uses a protein pump.
- Requires ATP.
Large Molecules
- Moved into and out of the cell through vesicles and vacuoles.
Endocytosis
- Moving materials INTO the cell.
- Phagocytosis: "Cellular eating."
- Pinocytosis: "Cellular drinking."
- Receptor-mediated endocytosis: Molecules bind to receptors on the outside of the cell membrane.
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Description
This quiz covers the concepts of membrane transport, focusing on passive transport methods including diffusion, simple diffusion, and facilitated diffusion. You'll learn about how substances like oxygen, carbon dioxide, and glucose move across cell membranes without the use of energy. Test your understanding of osmosis and the principles behind these essential biological processes.
