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Questions and Answers
What is the primary difference between diffusion and osmosis?
What is the primary difference between diffusion and osmosis?
In osmosis, water molecules move from an area of ____ to an area of ____.
In osmosis, water molecules move from an area of ____ to an area of ____.
What type of membrane allows the process of osmosis to occur?
What type of membrane allows the process of osmosis to occur?
What process is described as the net movement of water molecules through a selectively permeable membrane?
What process is described as the net movement of water molecules through a selectively permeable membrane?
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Which of the following correctly describes osmosis?
Which of the following correctly describes osmosis?
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During osmosis, what is the result of equal concentrations of solute on both sides of the membrane?
During osmosis, what is the result of equal concentrations of solute on both sides of the membrane?
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In an experiment, if a cell is placed in a solution with high solute concentration, what will likely happen to the cell?
In an experiment, if a cell is placed in a solution with high solute concentration, what will likely happen to the cell?
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Which of the following is NOT an example of osmosis?
Which of the following is NOT an example of osmosis?
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What happens to red blood cells when placed in a hypertonic solution?
What happens to red blood cells when placed in a hypertonic solution?
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Which term describes the process of red blood cells shrinking in a hypertonic solution?
Which term describes the process of red blood cells shrinking in a hypertonic solution?
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What is the main effect on plant cells when placed in a hypotonic solution?
What is the main effect on plant cells when placed in a hypotonic solution?
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What keeps plant cells from bursting in a hypotonic solution?
What keeps plant cells from bursting in a hypotonic solution?
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What term is used to describe the condition of plant cells being firm due to water uptake?
What term is used to describe the condition of plant cells being firm due to water uptake?
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In an isotonic solution, the movement of water into and out of the cells is characterized by which of the following?
In an isotonic solution, the movement of water into and out of the cells is characterized by which of the following?
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What is the effect of hypertonic solutions on red blood cells?
What is the effect of hypertonic solutions on red blood cells?
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What happens to the vacuoles of plant cells in a hypotonic solution?
What happens to the vacuoles of plant cells in a hypotonic solution?
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What happens to plant cells when they are placed in a hypertonic solution?
What happens to plant cells when they are placed in a hypertonic solution?
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What is the process called when plant cells lose water and shrink in a hypertonic solution?
What is the process called when plant cells lose water and shrink in a hypertonic solution?
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If plasmolysed plant cells are transferred to a hypotonic solution, what will likely occur?
If plasmolysed plant cells are transferred to a hypotonic solution, what will likely occur?
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What is the primary reason that water molecules diffuse into potato cells placed in a hypotonic solution?
What is the primary reason that water molecules diffuse into potato cells placed in a hypotonic solution?
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Which is a direct effect of osmosis in plant cells?
Which is a direct effect of osmosis in plant cells?
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How does turgidity of cells benefit plants?
How does turgidity of cells benefit plants?
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What occurs to a plant's leaves and stems when they undergo plasmolysis?
What occurs to a plant's leaves and stems when they undergo plasmolysis?
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What is likely to happen if a potato does not change mass in a sucrose solution?
What is likely to happen if a potato does not change mass in a sucrose solution?
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Study Notes
Movement of Substances Across the Plasma Membrane
- Living cells require substances from the external environment to perform life processes
- Cells also produce waste products that need to be removed
- Substances must be allowed to move into and out of the cell to maintain life processes
- The movement of substances into and out of a cell is regulated by the plasma membrane
Structure of Plasma Membrane
- The fluid mosaic model describes the plasma membrane's components:
- Proteins are embedded within a phospholipid bilayer, creating a mosaic pattern that constantly changes
- The phospholipid bilayer, proteins, and cholesterol are dynamic, not static, and form a flexible structure
- The fluid nature of the membrane and protein flexibility contribute to the membrane's adaptability and flexibility
Components of Plasma Membrane
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Phospholipid bilayer:
- Hydrophilic heads (attracted to water) face the extracellular and intracellular fluid
- Hydrophobic tails (repel water) face each other
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Proteins:
- Channel proteins form channels or canals, and carrier proteins transport substances across the membrane
- Glycoproteins and glycolipids are proteins and lipids that have carbohydrate chains attached
Permeability of Plasma Membrane
- The plasma membrane is a selectively permeable membrane, allowing some substances to pass freely, while others are restricted
- The phospholipid bilayer and proteins dictate the membrane's permeability for specific substances
- Hydrophobic (nonpolar) molecules can freely pass through the phospholipid bilayer
- Hydrophilic (polar) molecules are restricted due to their interaction with the hydrophobic tails
Passive Transport
- Passive transport doesn't require energy
- Substances move from high to low concentration (down the concentration gradient)
- Types of passive transport include:
- Simple diffusion: Small, nonpolar molecules passively move across the membrane
- Facilitated diffusion: Large or polar molecules move across the membrane with the assistance of membrane proteins
- Osmosis: Water passively moves from areas of high water potential to low water potential
Active Transport
- Active transport requires energy (ATP)
- Substances move from low to high concentration (against the concentration gradient)
- Carrier proteins transport the substances across the membrane
- Includes the sodium-potassium pump and proton pumps
Gaseous Exchange
- Simple diffusion is involved in the exchange of gases between alveoli and blood capillaries
- Carbon dioxide and oxygen pass from the blood capillary into the alveoli (or vice-versa) based on the concentration gradients of these substances
Reabsorption
- Water and certain solutes are reabsorbed across membranes through the action of osmosis and facilitated diffusion.
Absorption
- Water absorption by plant root hair cells occurs via osmosis
- Fructose absorption from the small intestine into the villi by facilitated diffusion.
- Absorption of glucose and amino acids in the villi is against the concentration gradient and uses active transport.
- Mineral ions are absorbed from the soil by plant root hair cells using active transport.
Isotonic, Hypotonic and Hypertonic Solutions
- Isotonic solutions have the same solute concentration as the cell cytoplasm, which results in no net water movement
- Hypotonic solutions have a lower solute concentration than the cell cytoplasm, resulting in net water movement into the cell, causing swelling
- Hypertonic solutions have a higher solute concentration than the cell cytoplasm, resulting in net water movement out of the cell, causing shrinkage
Liposomes
- Liposomes are vesicles containing aqueous solutions enclosed by a phospholipid bilayer
- Used to deliver drugs and other substances
- Used in cosmetics due to their ability to encapsulate active ingredients
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Description
This quiz covers the essential concepts of the plasma membrane, including the movement of substances across it, its structure as described by the fluid mosaic model, and the components that make it up. Understand how these elements work together to regulate cellular processes and maintain homeostasis.
