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Questions and Answers
What is the correct definition of the permeability coefficient (P)?
What is the correct definition of the permeability coefficient (P)?
- A measure of solute size and polarity
- Both B and C (correct)
- A coefficient that depends on the nature of the membrane
- The rate of diffusion through a membrane
Carrier proteins involved in facilitated diffusion can operate without the assistance of any external factors.
Carrier proteins involved in facilitated diffusion can operate without the assistance of any external factors.
False (B)
Name the two types of proteins that assist in facilitated diffusion.
Name the two types of proteins that assist in facilitated diffusion.
Carrier proteins and channel proteins
What type of transport mechanism does the Erythrocyte Anion Exchange Protein utilize?
What type of transport mechanism does the Erythrocyte Anion Exchange Protein utilize?
In facilitated diffusion, the conformational change of a carrier protein leads to the ______ release of the transported solute.
In facilitated diffusion, the conformational change of a carrier protein leads to the ______ release of the transported solute.
Aquaporins facilitate the passive transport of ions across the cell membrane.
Aquaporins facilitate the passive transport of ions across the cell membrane.
Match the following terms with their corresponding descriptions:
Match the following terms with their corresponding descriptions:
What is the primary role of channel proteins in the cell membrane?
What is the primary role of channel proteins in the cell membrane?
The movement of water through aquaporins is ____ compared to what would be expected due to its polarity.
The movement of water through aquaporins is ____ compared to what would be expected due to its polarity.
Match the following transport mechanisms with their description:
Match the following transport mechanisms with their description:
Which type of transport does not require energy input?
Which type of transport does not require energy input?
Active transport moves substances down their concentration gradient.
Active transport moves substances down their concentration gradient.
What is the primary factor that determines the movement of ions across a membrane?
What is the primary factor that determines the movement of ions across a membrane?
The diffusion of water across a selectively permeable membrane is known as __________.
The diffusion of water across a selectively permeable membrane is known as __________.
Match the following terms with their definitions:
Match the following terms with their definitions:
What happens to a plant cell in a hypotonic solution?
What happens to a plant cell in a hypotonic solution?
Solute movement across a membrane is unaffected by the properties of the solute.
Solute movement across a membrane is unaffected by the properties of the solute.
Identify a gas that can readily traverse the lipid bilayer by simple diffusion.
Identify a gas that can readily traverse the lipid bilayer by simple diffusion.
Flashcards
Anion exchange protein
Anion exchange protein
Facilitates exchange of Cl- and HCO3- in a 1:1 ratio.
Osmosis
Osmosis
Movement of water across a semipermeable membrane.
Aquaporins
Aquaporins
Transmembrane proteins allowing rapid water passage.
Ion channels
Ion channels
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Channel proteins
Channel proteins
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Rate of diffusion (v inward)
Rate of diffusion (v inward)
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Facilitated diffusion
Facilitated diffusion
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Carrier proteins
Carrier proteins
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Conformational change
Conformational change
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GLUT1 transport
GLUT1 transport
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Passive Transport
Passive Transport
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Active Transport
Active Transport
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Concentration Gradient
Concentration Gradient
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Electrochemical Potential
Electrochemical Potential
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Membrane Potential (Vm)
Membrane Potential (Vm)
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Solute Properties
Solute Properties
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Study Notes
Membrane Transport Overview
- Membrane transport encompasses passive and active processes.
- Passive transport occurs along concentration gradients without energy input.
- Active transport moves substances against their concentration gradients, requiring energy.
Passive Transport Details
- Passive diffusion involves movement of a substance down its concentration gradient.
- Facilitated diffusion employs transport proteins to aid movement down a concentration gradient.
Active Transport Details
- Active transport involves movement against a concentration gradient, using energy.
Factors Affecting Transport
- Solute properties (size, polarity) influence transport.
- Relative solute concentrations determine the direction of movement.
- Specific transmembrane proteins affect the rate and types of substances transported.
- Energy sources are needed for active transport.
Movement Across Membranes
- Movement across membranes depends on the solute's chemical potential (concentration and electric charge).
- Simple diffusion and facilitated diffusion follow exergonic paths down concentration gradients.
- Active transport entails endergonic movement against gradients, using energy.
Electrochemical Potential
- Electrochemical potential dictates ion transport, combining concentration and charge gradients.
- Membrane potential (Vm) arises from ionic charge imbalances across membranes.
Simple vs. Facilitated Diffusion
- Simple diffusion involves direct movement of small nonpolar/uncharged substances across the membrane.
- In facilitative diffusion, transport proteins assist large or polar substances to cross membranes.
Osmosis Explained
- Osmosis is water movement across a selectively permeable membrane from a region of lower solute concentration to a region of higher solute concentration.
- Osmolarity relates the concentration of solutes to water movement.
Tonicity
- Hypotonic solution has lower solute concentration outside the cell, causing water influx.
- Hypertonic solution has higher solute concentration outside the cell, inducing water efflux.
- Isotonic solution has balanced solute concentrations, resulting in no net water movement.
Plant Cell Response to Tonicity
- Plant cells with cell walls maintain turgor pressure by managing water movement in hypotonic solutions.
- Plasmolysis refers to cell wall separation from the plasma membrane in hypertonic solutions.
Animal Cell Response to Tonicity
- Animal cells without cell walls regulate osmolarity by ion pumping to maintain solute balance.
Rate of Simple Diffusion
- Simple diffusion rate directly correlates with the concentration gradient.
- Diffusion rate (Vinward) = Permeability coefficient (P) × Concentration difference (Δ[S]) across membrane.
Facilitated Diffusion
- Facilitated diffusion involves protein-mediated movement, with transport proteins like carrier and channel proteins operating.
- Carrier proteins alternate between conformational states to bind and release solute molecules.
- Carrier protein behavior is comparable to enzymes, showing specificity and kinetic properties involving substrate binding and release.
- Carrier protein activities can be regulated.
- Carrier transport in cells includes uniport, symport, and antiport. GLUT1 is an example of a uniporter.
Channel Proteins
- Channel proteins facilitate diffusion by creating hydrophilic channels across the membrane.
- Aquaporins, ion channels, and porins are specific types of channels.
Aquaporins
- Aquaporins facilitate exceptionally rapid water movement across membranes.
- Aquaporins were discovered more recently.
Ion Channels
- Ion channels allow rapid passage of specific ions through hydrophilic pore channels.
- Ion channels demonstrate selectivity based on size and charged amino acid residues.
- Ion channel activity is dependent on electrochemical gradients.
Porins
- Porins are transmembrane proteins forming large, relatively non-specific channels.
- Porin proteins adopt a β barrel structure.
- Porins are key for solute transport in certain cellular compartments.
Transport Rate of Facilitated Diffusion
- Facilitated diffusion rate is not linearly dependent on concentration because of protein saturation.
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