Lecture 3-4: Ion Channels and Membrane Potential

Ion Channels

Proteins that facilitate the passage of ions across a cellular membrane, often selective for specific ions.

Membrane Potential

The electrical potential difference across a cell membrane due to the distribution of ions.

Nernst Equation

A mathematical formula used to calculate the equilibrium potential for a specific ion based on its concentration gradient.

Active Transport

The movement of ions or molecules across a cell membrane through the use of energy, typically ATP.

Potassium Leak Channels

Ion channels that open randomly, allowing K+ ions to move out of the cell, contributing to resting membrane potential.

Electrochemical Equilibrium

The state where the electrical gradient and concentration gradient for a specific ion balance each other, resulting in no net movement of that ion.

Selectivity Filter

A narrow region within an ion channel that determines which ions can pass based on their size and charge.

Ligand-Gated Channels

Ion channels that open in response to the binding of a specific molecule (ligand), allowing ions to flow through.

Mechanically-Gated Channels

Ion channels that open or close in response to mechanical forces or pressure, commonly found in sensory cells.

Na+-K+ ATPase

A pump that actively transports Na+ out of and K+ into cells, crucial for maintaining the membrane potential.

Depolarization

A decrease in the membrane potential, making the inside of the cell less negative relative to the outside.

Hyperpolarization

An increase in the membrane potential, making the inside of the cell more negative relative to the outside.

Sodium-Potassium Pump

An enzyme that pumps sodium out and potassium into the cell, vital for maintaining resting membrane potential.

Cation

A positively charged ion, such as Na+ or K+.

Anion

A negatively charged ion, such as Cl-.

Hydration Shell

The sphere of water molecules surrounding an ion in solution, affecting its ability to pass through ion channels.

Turgor Pressure

The pressure exerted by fluid in the central vacuole of plant cells, contributing to cell rigidity and support.

Threshold Potential

The membrane potential that must be reached for an action potential to be generated in a neuron.

Patch Clamp Method

An experimental technique used to study the ionic currents that flow through individual ion channels.

Resting Membrane Potential

The membrane potential of a cell at rest, typically around -70mV for neurons, determined mainly by potassium ion concentration.

Equilibrium Potential

The membrane potential at which the net movement of a specific ion across the membrane is zero.

Electrolyte Bath

A solution used in patch clamp experiments that allows for the measurement of ionic currents through channels.