Cell Biology: Membrane Transport Mechanisms

The movement of a molecule across a membrane from a region of high concentration to a region of low concentration, without the need for energy. Driven by the concentration gradient.

Proteins embedded in the cell membrane that facilitate the passive transport of specific molecules across the membrane, down their concentration gradient.

Transmembrane proteins that allow the rapid passage of specific ions across the cell membrane. They are selective for certain ions based on size and charge.

A type of ion channel that opens in response to changes in the membrane potential, like a voltage switch.

A type of ion channel that opens when a specific ligand binds to it, like a key opening a lock.

Specialized channels that allow water to pass through the cell membrane. They are selective for water, preventing the passage of ions.

A mechanism that uses the energy released by the movement of one molecule down its concentration gradient to drive the movement of another molecule against its gradient. This is a form of active transport.

A secondary active transport mechanism where two molecules move in the same direction across the membrane.

A secondary active transport mechanism where two molecules move in opposite directions across the membrane.

A type of transporter that actively pumps Na⁺ ions out of the cell, using energy from ATP hydrolysis. This maintains a low concentration of Na⁺ inside the cell.

The movement of water across a selectively permeable membrane from a region of high water concentration (low solute concentration) to a region of low water concentration (high solute concentration).

The pressure that must be applied to a solution to prevent the inward flow of water across a semipermeable membrane. It is a measure of the solution's concentration.

The movement of molecules across a membrane against their concentration gradient, which requires energy from ATP hydrolysis.

A protein embedded in the cell membrane that binds to a specific molecule and undergoes conformational changes to transport it across the membrane.

A specialized type of active transport where a single molecule moves across the membrane, driven by the energy from ATP hydrolysis.

Maintains low intracellular Ca²⁺ concentration. Regulates acidity in stomach cells and organelles like lysosomes.

A primary active transport system that uses ATP to pump 3 Na⁺ ions out of the cell and 2 K⁺ ions into the cell, both against their concentration gradients.

The movement of molecules across a membrane from an area of high concentration to an area of low concentration, without requiring energy input.

A type of secondary active transport where the transported molecule moves in the same direction as the driving ion (e.g., Na⁺-glucose co-transporters).

A type of secondary active transport where the transported molecule moves in the opposite direction as the driving ion (e.g., Na⁺-H⁺ anti-transporters).

A large family of ATP-binding cassette (ABC) transporters that are important for importing essential nutrients and exporting toxins, drugs, and antibiotics.

A specific ABC transporter that is overexpressed in tumor cells and contributes to drug resistance by pumping chemotherapeutic drugs out of the cell.

An ABC transporter that is responsible for regulating chloride transport in the lungs and other tissues.

The ability of a cell membrane to allow some molecules to pass through while blocking others.