ion channels Flashcards
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What are the main classes of proteins found at the plasma membrane?
Transporters: Facilitate movement of molecules through the membrane.
Linkers: Connect cytoskeleton and extracellular matrix.
Receptors: Mediate signal transduction and molecule recognition.
Enzymes: Catalyze reactions that transform substrates into products.
What functions do plasma membrane proteins serve?
- Transport of molecules through the membrane.
- Enzymatic activity transforming substrates into products.
- Molecule recognition and signal transduction.
- Cell-cell recognition through glycan interactions.
- Intercellular joining of adjacent cells.
What is primary active transport?
Primary active transport moves molecules against their electrochemical gradient using direct energy from ATP, requiring carrier proteins that exhibit saturation, stereospecificity, and competition.
What is secondary active transport?
Secondary active transport moves molecules against their electrochemical gradient by using indirect energy input, often coupling with another molecule’s movement, and also requires carrier proteins with similar properties to primary transport.
How do ion channels function?
Ion channels transport ions across the plasma membrane and regulate membrane potential, which is the voltage difference between the interior and exterior of the cell.
What is membrane potential (Vm)?
Membrane potential is the voltage difference across the plasma membrane due to the movement of ions. It results in a net negative charge inside the cell, with typical mammalian cells having a resting potential around -50 mV.
Describe the sodium-potassium pump mechanism.
- Cytoplasmic Na⁺ binds to the Na⁺/K⁺ pump.
- The pump is phosphorylated by ATP.
- Conformational change occurs, releasing Na⁺.
- K⁺ is released from the pump.
- The pump returns to its original conformation.
- Extracellular K⁺ binds to the pump, leading to dephosphorylation.
What experimental method is used to investigate ion channels?
Patch-clamp electrophysiology is used to measure the influx of ions and changes in electrical current, providing insights into ion channel function.
How is membrane potential measured?
An electrode tip impales the cell’s plasma membrane to measure the voltage difference between the inside and outside of the cell.
What does the Nernst equation describe?
The Nernst equation calculates the equilibrium potential for a particular ion, taking into account the concentration gradient across a permeable barrier.
What does it mean if there is no change in equilibrium potential?
No ion movement occurs when the system is at equilibrium, with the ion flux in and out of the cell balanced, resulting in no net change in the membrane potential.
What is the resting membrane potential (V_rest)?
The resting membrane potential is the phase between action potentials, characterized by a net negative charge inside the cell compared to the outside, typically around -50 mV in mammalian cells.
What is the Nernst equation, and what does it calculate?
The Nernst equation calculates the equilibrium potential (E_ion) for a specific ion across a membrane, based on the ion’s concentration gradient. It is expressed as:
Eion = RT/zF In (ion outside/ ion inside)
Significance: The Nernst equation helps predict the direction of ion movement across the membrane and contributes to understanding the membrane potential in excitable cells.
