Membrane Transport Flashcards

A set of vocabulary flashcards covering key terms for membrane transport mechanisms, including passive transport, active transport, tonicity, and bulk transport.

Concentration Gradient

The difference in concentration of molecules across a space.

Selective Permeability

A property of biological membranes that allows them to regulate transport across cellular boundaries, allowing small nonpolar molecules like $\text{CO}_2$, $\text{O}_2$, and $\text{N}_2$ to cross easily while restricting ions and large polar molecules.

Passive Transport

The movement of substances across a membrane down their concentration gradient (from high to low concentration) without requiring cellular energy ($\text{ATP}$).

Diffusion

The movement of solutes or molecules from an area of high concentration to an area of low concentration down a concentration gradient.

Osmosis

The diffusion of water ($\text{H}_2\text{O}$) across a selectively permeable membrane.

Hypotonic Solution

An external environment that has a lower solute concentration compared to the inside of the cell, causing the cell to take in water.

Hypertonic Solution

An external environment that has a higher solute concentration compared to the inside of the cell, causing water to leave the cell.

Isotonic Solution

An external environment that has the same solute concentration as the inside of the cell, resulting in no net change in water.

Facilitated Diffusion

Passive transport that uses transport proteins (channel or carrier proteins) to assist hydrophilic substances, ions, and polar molecules in crossing the membrane.

Aquaporin

A channel protein embedded in the cell membrane that specifically allows the passage of water ($\text{H}_2\text{O}$).

Active Transport

The transport of substances across a membrane against their concentration gradient (from low to high concentration), requiring cellular energy ($\text{ATP}$).

Electrogenic Pump

A transport protein that generates voltage across a membrane by pumping ions.

Sodium-Potassium Pump ($\text{Na}^+/\text{K}^+$ Pump)

An electrogenic pump that actively pumps $\text{Na}^+$ out of the cell and $\text{K}^+$ into the cell, which is important for nerve transmission.

Proton Pump

An electrogenic pump that actively pushes protons ($\text{H}^+$) across a membrane, such as in mitochondria for $\text{ATP}$ production.

Cotransport

A mechanism where a membrane protein enables the downhill diffusion of one solute to drive the uphill transport of another solute against its concentration gradient.

Bulk Transport

The cellular transport process used for moving proteins, polysaccharides, and large molecules across the cell membrane.

Endocytosis

A mechanism of bulk transport where the cell takes in macromolecules and particulate matter by forming new vesicles from the plasma membrane.

Exocytosis

A mechanism of bulk transport where vesicles fuse with the plasma membrane to secrete their contents out of the cell.