active cell transport

Vocabulary practice flashcards covering membrane transport mechanisms, fluid compartments, electrophysiology, cellular organelles, protein synthesis, and DNA replication based on lecture notes.

Electrical Gradient

A difference in electrical charge ($+$ or $-$) between two connected regions or areas.

Diffusion

A passive transport process in which solute molecules move down their concentration gradient from an area of higher solute concentration to an area of lower solute concentration until equilibrium is reached.

Simple Diffusion

A type of passive transport where mostly nonpolar solutes pass straight through the phospholipid bilayer without assistance from membrane proteins.

Facilitated Diffusion

A passive transport process where charged or polar solutes cross the phospholipid bilayer down their gradient with the help of membrane proteins such as channels or carriers.

Osmosis

The passive process in which solvent (water) moves across a selectively permeable membrane from a less concentrated solution (fewer solutes, more water) into a more concentrated solution (more solutes, less water).

Osmotic Pressure (OP)

The force exerted by impermeable solutes, defined as the pressure that must be applied to a solution to prevent water from moving into it by osmosis; higher solute concentration creates higher osmotic pressure.

Tonicity

A measure comparing the solute concentrations of two solutions—determined specifically by solutes that cannot cross the plasma membrane—that reflects the ability of the ECF to make water move into or out of a cell.

Isotonic Solution

A solution in which the ECF has approximately the same solute concentration as the cytosol, resulting in no net water movement and no cellular volume changes.

Hypertonic Solution

A solution where the solute concentration of the ECF is higher than that inside the cell, creating an osmotic pressure gradient that pulls water out of the cell and causes it to shrivel or crenate.

Hypotonic Solution

A solution where the solute concentration of the ECF is lower than that inside the cell, pulling water inward by osmosis so the cell swells and may rupture or lyse.

Primary Active Transport

A transport process in which a membrane pump directly uses energy released from ATP hydrolysis to transport solutes against their concentration gradients across the membrane.

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

The major primary active transport pump that uses ATP hydrolysis to pump three $\text{Na}^+$ ions out of the cell and two $\text{K}^+$ ions into the cell, maintaining steep ionic gradients across the plasma membrane.

Secondary Active Transport

An active transport mechanism that uses energy from ATP hydrolysis indirectly; a primary pump establishes a concentration gradient of one substance (such as $\text{Na}^+$), and a carrier harnesses that gradient's potential energy to drive the transport of another substance (such as glucose) against its gradient.

Transport Vesicle

A membranous sac enclosed by a phospholipid bilayer formed from pinched-off cell membranes, used to actively move large macromolecules into or out of cells.

Endocytosis

An active vesicular transport process that brings extracellular fluid, large molecules, or entire cells into the interior of the cell.

Phagocytosis

A type of endocytosis referred to as 'cell-eating' in which phagocytes extend pseudopods to surround and ingest large particles or foreign cells into a vesicle called a phagosome.

Pinocytosis

A form of endocytosis known as 'cell-drinking' occurring in all cells, where droplets of fluid from the ECF are engulfed by folding in protein-coated pits to form transport vesicles.

Receptor-Mediated Endocytosis

A specific form of endocytosis where target ligands bind to specific receptors in protein-coated pits of the plasma membrane, triggering the formation of a vesicle containing the bound molecules.

Exocytosis

An active vesicular transport process where transport vesicles fuse with the plasma membrane to release their contents into the ECF (secretion) or incorporate their components into the plasma membrane.

Resting Membrane Potential (RMP)

The voltage or difference in electrical potential across the plasma membrane of a cell at rest, which has a negative value (such as $-70\,\text{mV}$ to $-90\,\text{mV}$) indicating that the cytosol side is more negatively charged than the ECF side.