Membrane Transport and Electrochemical Gradients

Flashcards covering key vocabulary related to membrane transport, electrochemical gradients, and ion movement across cell membranes based on lecture notes.

Membrane Transport

The process by which substances move across cell membranes, often involving specific proteins.

Electrochemical Gradient

The combined influence of a concentration gradient (chemical force) and an electrical potential difference (electrical force) on an ion across a membrane.

Membranes

Cellular structures that act as barriers separating ions and macromolecules, enable energy transformations, and convey information.

Hydrophobic Interactions

The association of non-polar molecules with one another because water becomes more ordered around individual non-polar molecules, and this ordering is reduced when the non-polar molecules associate.

Osmotic Force

The net movement of water across a semipermeable membrane due to differences in solute concentrations.

Ion Channel

A transmembrane protein that forms a pore allowing specific ions to pass across a cell membrane, driven by concentration and/or charge differences.

Chemical Force (ions)

The force causing ions to move across membranes due to differences in their concentration gradients.

Electrical Force (ions)

The force causing ions to move across membranes due to differences in charge across the membrane.

Membrane Potential (Vm)

A difference in charge distribution across a lipid bilayer, conventionally defined as the potential inside the cell minus the potential outside (Vm = Vin – Vout).

Nernst Equation

An equation used to calculate the equilibrium potential (Veq) for a specific ion across a membrane, where Veq = 58mV • Log10(Co/Ci) for a monovalent ion at room temperature.

Ion-selective Channel

An ion channel designed to allow only specific types of ions (e.g., K+, Na+) to pass through.

Resting Membrane Potential

The steady-state membrane potential of a cell where the inward and outward currents of various ions across the membrane are balanced.

Gated Channel

An ion channel whose opening and closing is regulated by changes in its conformation, allowing control over ion flow.

Neurons

Specialized cells that transmit information by utilizing rapid changes in their membrane potential.

Chemiosmotic Coupling

A process used by mitochondria and chloroplasts where energy from electron transport is used to pump protons across a membrane, creating an electrochemical gradient that then drives ATP synthesis.

Proton-motive Force

The electrochemical gradient of protons (H+) across a membrane, which stores energy used to drive processes like ATP synthesis.

Free Energy Change for Concentration Gradient (∆Gconc)

The change in free energy for one mole of ions moving across a membrane due to a concentration difference, calculated as –RT ln (Co/Ci).

Free Energy Change for Electrical Force (∆Gvolt)

The change in free energy for charged ion movement due to an electrical potential, calculated as zFV.

Equilibrium (ion movement)

The state where the chemical and electrical forces acting on an ion across a membrane are balanced, resulting in no net movement of that ion (∆Gvolt + ∆Gconc = 0).