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What type of proteins facilitate the majority passage of water across a cell membrane?
What type of proteins facilitate the majority passage of water across a cell membrane?
Charged substances can easily pass through a lipid bilayer.
Charged substances can easily pass through a lipid bilayer.
False
What is the process called when water diffuses across a selectively permeable membrane?
What is the process called when water diffuses across a selectively permeable membrane?
Osmosis
In a ______ solution, solute concentration is greater than that inside the cell; the cell loses water.
In a ______ solution, solute concentration is greater than that inside the cell; the cell loses water.
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Match the following terms with their definitions:
Match the following terms with their definitions:
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Which of the following describes passive transport?
Which of the following describes passive transport?
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Transport proteins are specific for the substance they move.
Transport proteins are specific for the substance they move.
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What happens to cells in a hypotonic solution?
What happens to cells in a hypotonic solution?
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Cells recognize each other by binding to surface molecules, often ______, on the plasma membrane.
Cells recognize each other by binding to surface molecules, often ______, on the plasma membrane.
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What is the term for the ability of a solution to cause a cell to gain or lose water?
What is the term for the ability of a solution to cause a cell to gain or lose water?
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What is the primary function of phospholipids in the plasma membrane?
What is the primary function of phospholipids in the plasma membrane?
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Unsaturated fatty acids contribute to a more fluid membrane structure than saturated fatty acids.
Unsaturated fatty acids contribute to a more fluid membrane structure than saturated fatty acids.
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What role does cholesterol play in membrane fluidity?
What role does cholesterol play in membrane fluidity?
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Phospholipids are __________ molecules, containing both hydrophobic and hydrophilic regions.
Phospholipids are __________ molecules, containing both hydrophobic and hydrophilic regions.
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Match each protein type with its description:
Match each protein type with its description:
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Which statement regarding membrane fluidity is incorrect?
Which statement regarding membrane fluidity is incorrect?
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Most lipids and some proteins in the plasma membrane can flip-flop transversely across the membrane easily.
Most lipids and some proteins in the plasma membrane can flip-flop transversely across the membrane easily.
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What is the function of transmembrane proteins in the plasma membrane?
What is the function of transmembrane proteins in the plasma membrane?
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What is the term for the control of water balance in organisms?
What is the term for the control of water balance in organisms?
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At warm temperatures, cholesterol __________ the movement of phospholipids.
At warm temperatures, cholesterol __________ the movement of phospholipids.
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Which of the following correctly describes the fluid mosaic model?
Which of the following correctly describes the fluid mosaic model?
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A plant cell becomes flaccid in a hypotonic environment.
A plant cell becomes flaccid in a hypotonic environment.
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What happens to a plant cell in a hypertonic solution?
What happens to a plant cell in a hypertonic solution?
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In facilitated diffusion, ____ proteins speed up the passive movement of molecules across the plasma membrane.
In facilitated diffusion, ____ proteins speed up the passive movement of molecules across the plasma membrane.
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Match the type of transport to its characteristic:
Match the type of transport to its characteristic:
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Which process requires energy in the form of ATP?
Which process requires energy in the form of ATP?
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Aquaporins are channel proteins that facilitate the diffusion of water.
Aquaporins are channel proteins that facilitate the diffusion of water.
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What occurs during plasmolysis in plant cells?
What occurs during plasmolysis in plant cells?
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The _____ pump is an example of active transport.
The _____ pump is an example of active transport.
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Which of the following is NOT a type of passive transport?
Which of the following is NOT a type of passive transport?
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What type of molecules does simple diffusion primarily transport?
What type of molecules does simple diffusion primarily transport?
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Facilitated diffusion can use both carrier and channel proteins.
Facilitated diffusion can use both carrier and channel proteins.
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What is the term for the simultaneous movement of two distinct molecules across a membrane by one protein?
What is the term for the simultaneous movement of two distinct molecules across a membrane by one protein?
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In ________, the cell engulfs solid particles in a vacuole.
In ________, the cell engulfs solid particles in a vacuole.
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Match the types of transport with their descriptions:
Match the types of transport with their descriptions:
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Which type of endocytosis involves the binding of ligands to receptors?
Which type of endocytosis involves the binding of ligands to receptors?
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Active transport requires energy to move substances against their concentration gradient.
Active transport requires energy to move substances against their concentration gradient.
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What are the two types of transport movements in co-transport?
What are the two types of transport movements in co-transport?
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In ________, the transport vesicles migrate to the membrane and release their contents.
In ________, the transport vesicles migrate to the membrane and release their contents.
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Which type of transport is primarily involved in the movement of water-soluble molecules?
Which type of transport is primarily involved in the movement of water-soluble molecules?
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Study Notes
Cell Membrane Structure & Function
- Phospholipids are the most abundant lipids in the plasma membrane
- Phospholipids are amphipathic, meaning they have both hydrophobic and hydrophilic regions.
- The fluid mosaic model describes the plasma membrane as a fluid structure with various proteins embedded in it.
Fluidity of Membranes
- Phospholipids can move within the bilayer.
- Most lipids and some proteins drift laterally or rotate.
- Flip-flop (transverse movement) across the membrane is rare.
Temperature and Membrane Fluidity
- As temperatures increase, membranes transition from a solid (gel) state to a more fluid state.
- Membranes with shorter fatty acid chains are more fluid than those with longer chains.
- Shorter fatty acid chains result in less surface area for van der Waals or hydrophobic interactions between neighboring phospholipids.
- Membranes rich in unsaturated fatty acids are more fluid than those rich in saturated fatty acids due to kinks introduced by the unsaturated carbons. The kinks prevent tight packing of the phospholipids.
Cholesterol in Animal Cell Membranes
- Cholesterol affects membrane fluidity at different temperatures, acting as a fluidity buffer.
- At warm temperatures, cholesterol restrains phospholipid movement, decreasing membrane fluidity.
- At cool temperatures, cholesterol prevents tight packing, increasing membrane fluidity.
Membrane Proteins and Their Functions
- Membranes are a collage of different proteins embedded in the fluid matrix of the lipid bilayer.
- Proteins determine most of the membrane's specific functions.
- Peripheral proteins are bound to the membrane surface.
- Integral proteins penetrate the hydrophobic core, and transmembrane proteins span the membrane.
- Hydrophobic regions of integral proteins consist of stretches of nonpolar amino acids, often coiled into alpha helices.
- Membrane proteins have six major functions: transport, enzymatic activity, signal transduction, cell-cell recognition, intercellular joining, and attachment to the cytoskeleton and extracellular matrix.
Role of Membrane Carbohydrates in Cell-Cell Recognition
- Cells recognize each other by binding to surface molecules, often carbohydrates on the plasma membrane.
- Membrane carbohydrates may be covalently bonded to lipids (glycolipids) or more commonly to proteins (glycoproteins).
- Carbohydrate chains vary among species, individuals, and even cell types.
Membrane Structure and Selective Permeability
- Cells exchange materials with their surroundings through the plasma membrane, which is selectively permeable.
- Hydrophobic molecules can dissolve in the lipid bilayer and pass rapidly through the membrane.
- Water molecules can also pass easily.
- Polar molecules and charged substances (ions) do not cross the membrane easily.
Transport Proteins
- Transport proteins allow hydrophilic substances to pass across the membrane.
- Channel proteins have a hydrophilic channel that certain molecules or ions can use as a tunnel.
- Aquaporins are channel proteins that facilitate the passage of water.
- Carrier proteins bind to molecules and change shape to shuttle them across the membrane.
- Transport proteins are specific for the substance they move.
Passive Transport
- Diffusion is the tendency of molecules to spread out evenly into the available space.
- Diffusion of a population of molecules may exhibit a net movement in one direction.
- Substances diffuse down their concentration gradients (from high to low concentration).
- Diffusion across a biological membrane is passive transport as it doesn't require energy.
- Dynamic equilibrium happens when an equal number of molecules cross the membrane in each direction.
Osmosis
- Osmosis is the diffusion of water across a selectively permeable membrane.
- Water diffuses from a region of lower solute concentration to a region of higher solute concentration.
- Osmosis is specifically the movement of water, not other molecules.
Tonicity and Water Balance in Cells Without Cell Walls
- Tonicity describes the ability of a solution to cause a cell to gain or lose water.
- Isotonic: solute concentration is the same inside and outside the cell, no net water movement.
- Hypertonic: solute concentration is greater outside the cell, water moves out, cell loses water.
- Hypotonic: solute concentration is less outside the cell, water moves in, cell gains water (and can potentially lyse).
Water Balance in Cells With Cell Walls
- Cell walls help maintain water balance.
- In hypotonic solutions, plant cells swell until the wall opposes uptake, becoming turgid (firm).
- In isotonic solutions, there's no net water movement, and cells become flaccid (limp).
- In hypertonic solutions, plant cells lose water, and the membrane pulls away from the wall, a usually lethal effect called plasmolysis.
Facilitated Diffusion
- Transport proteins speed passive movement of molecules across the membrane.
- Channel proteins provide corridors for specific molecules or ions.
- Examples include aquaporins (for water) and ion channels (that open or close in response to a stimulus.)
- Carrier proteins change shape to shuttle solutes across the membrane.
Active Transport
- Active transport moves substances against their concentration gradients, requiring energy (usually ATP).
- The sodium-potassium pump is an example of active transport.
Cotransport
- Cotransport is the simultaneous movement of two distinct molecules across a biological membrane by a single protein.
- Symport moves the molecules in the same direction.
- Antiport moves the molecules in opposite directions.
Bulk Transport
- Exocytosis occurs when transport vesicles migrate to the membrane, fuse with it, and release their contents.
- Endocytosis is when the cell takes in macromolecules by forming vesicles from the plasma membrane.
- Endocytosis involves phagocytosis ("cellular eating").
- Endocytosis includes pinocytosis ("cellular drinking").
- Receptor-mediated endocytosis is also a form of endocytosis.
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Description
This quiz focuses on cell membrane transport proteins and the various solutions that affect cell water movement. Test your knowledge on concepts such as osmosis, passive transport, and phospholipid functions in the plasma membrane. Perfect for students studying cell biology topics.
