APK2105C Chapter 4: Cell Membrane Transport Flashcards

These flashcards cover the vocabulary and key concepts of cell membrane transport from APK2105C Chapter 4, including driving forces, types of passive and active transport, osmosis, tonicity, and vesicular transport.

Passive Transport

Spontaneous movement of molecules across a membrane from high to low energy (down the electrochemical gradient) without the requirement of ATP.

Active Transport

Movement of molecules in a preferred direction or against their gradient that requires the use of ATP; includes primary and secondary active transport.

Chemical Driving Force

A force where the rate of transport depends on the size of the concentration gradient across the membrane.

Electrical Driving Force

A force that affects charged particles (ions) only, based on the principle that opposites attract and likes repel.

Membrane Potential ($V_m$)

The difference in electrical potential across the plasma membrane, where the sign is determined by the net charge inside the cell.

Electrochemical Driving Force

The total force acting on an ion, which is the sum of the chemical and electrical driving forces.

Equilibrium Potential ($E_X$)

The membrane potential at which the electrical driving force exactly opposes and balances the chemical driving force, resulting in no net movement of the ion.

$$E_{Na}$$

The equilibrium potential for Sodium, which is $+60\,mV$.

$$E_K$$

The equilibrium potential for Potassium, which is $-94\,mV$.

Net Flux

The rate of transport or the overall movement of molecules across a membrane.

Simple Diffusion

The spontaneous transport of molecules across the plasma membrane influenced by the magnitude of the driving force, surface area, and membrane permeability.

Facilitated Diffusion

Passive transport requiring a transmembrane protein carrier where the gradient dictates net flux and the system can reach saturation.

Diffusion Through Channels

Passive transport through transmembrane proteins such as aquaporins and ion channels that can be regulated to be open or closed.

Primary Active Transport

Transport where ATP is used directly, and the pumps act as both carriers and ATPase enzymes to hydrolyze ATP.

Secondary Active Transport

Transport powered by an electrochemical gradient previously created by primary active transport, such as sodium-linked glucose transport.

Cotransport

A form of secondary active transport where two substances move in the same direction across the membrane.

Countertransport

A form of secondary active transport where two substances move in opposite directions, such as the sodium-proton exchange.

Osmosis

The passive flow of water across a membrane down its own concentration gradient, which is unaffected by membrane potential ($V_m$).

Osmolarity

The total solute particle concentration of a solution, where $1\,Mole$ of solute equals $1\,Osmolar\ (Osm)$, and particles that dissociate increase this value.

Iso-osmotic

Two solutions that have an equal total concentration of permeant and impermeant solutes ($300\,mOsm$).

Hyperosmotic

A solution whose total concentration of solutes is higher ($>300\,mOsm$) than another solution.

Hypo-osmotic

A solution whose total concentration of solutes is lower ($<300\,mOsm$) than another solution.

Osmotic Pressure ($\pi$)

An expression of total solute concentration where water moves up the pressure gradient (from low to high osmotic pressure).

Tonicity

The concentration of impermeant solutes relative to the intracellular fluid, which determines whether a cell will shrink or swell.

Isotonic

A solution containing a concentration of impermeant solutes equal to the intracellular fluid ($300\,mOsm$).

Hypotonic

A solution with a lower concentration of impermeant solutes than the intracellular fluid ($<300\,mOsm$), causing the cell to swell.

Hypertonic

A solution with a higher concentration of impermeant solutes than the intracellular fluid ($>300\,mOsm$), causing the cell to shrink.

Endocytosis

The process of bringing molecules from the extracellular fluid into the cell via the formation of an endosome.

Phagocytosis

A specific type of endocytosis where a cell membrane engulfs a particle to form a phagosome.

Pinocytosis

A non-specific form of endocytosis where the cell takes in dissolved molecules from the extracellular fluid.

Receptor-Mediated Endocytosis

A specific type of endocytosis where molecules bind to receptors in clathrin-coated pits.

Exocytosis

The process where molecules packaged in secretory vesicles inside the cell are released into the extracellular fluid.

Absorption

The epithelial transport of materials from the external environment into the internal environment.

Secretion

The epithelial transport of materials from the internal environment to the external environment.

Apical Membrane

The portion of the epithelial cell membrane that faces the lumen.

Basolateral Membrane

The portion of the epithelial cell membrane that faces the interstitial fluid and blood.

Transcytosis

The transport of macromolecules across epithelial cells involving endocytosis at one membrane and exocytosis at the opposite membrane.