CHP4 MOVEMENT ACROSS CELL MEMBRANES

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    What is a concentration gradient (along/with)?

    Movement from high to low concentration without ATP.

    What is a concentration gradient (against)?

    Movement from low to high concentration requiring ATP.

    What defines simple diffusion?

    Passive movement until equilibrium is reached.

    What is a solvent?

    The liquid that dissolves a substance.

    What is a solute?

    The material that is dissolved in a solvent.

    What is net flux?

    Difference in one-way fluxes of a solute across a boundary.

    What does the permeability coefficient indicate?

    How easily a molecule diffuses through a membrane.

    What is the lipid bilayer's role in diffusion?

    Limits diffusion due to its hydrophobic interior.

    How do lipophilic molecules behave in the lipid bilayer?

    They diffuse rapidly due to being nonpolar.

    What characterizes hydrophilic molecules?

    They do not easily diffuse through the lipid bilayer.

    What is an ion channel?

    A protein that allows specific ions to cross the membrane.

    What is membrane potential?

    Separation of electrical charge across the plasma membrane.

    What is a gated channel?

    An ion channel regulated to control ion movement.

    What triggers ligand-gated channels?

    Binding of a chemical messenger.

    What causes voltage-gated channels to open?

    Changes in membrane potential.

    What is mediated transport?

    Movement of solutes via transporters due to size or polarity.

    What is a transporter?

    A protein that binds solute and changes shape to transport it.

    What does saturation in transporters indicate?

    Maximum flux has been reached across the membrane.

    What is facilitated diffusion?

    Transport from high to low concentration using a transporter.

    What is active transport?

    Movement against a concentration gradient using energy.

    What distinguishes primary active transport?

    Directly uses ATP as its energy source.

    What is secondary active transport?

    Uses energy from an electrochemical gradient for movement.

    What is cotransport (symport)?

    Solutes move in the same direction across the membrane.

    What is countertransport (antiport)?

    Solutes move in opposite directions across the membrane.

    What does the Na⁺/K⁺ ATPase pump do?

    Moves 3 Na⁺ out and 2 K⁺ into the cell using ATP.

    What is osmosis?

    Net diffusion of water across a membrane.

    What are aquaporins?

    Proteins that facilitate water movement across membranes.

    What is osmotic pressure?

    Ability of a solution to pull water.

    What defines an isotonic solution?

    Same solute concentration as normal extracellular fluid.

    What is a hypotonic solution?

    Lower solute concentration than normal extracellular fluid.

    What is a hypertonic solution?

    Higher solute concentration than normal extracellular fluid.

    What is endocytosis?

    Movement of molecules into the cell via vesicles.

    What is pinocytosis?

    Fluid endocytosis, or 'cell drinking'.

    What is phagocytosis?

    Brings large particles into the cell, or 'cell eating'.

    What is receptor-mediated endocytosis?

    Requires specific receptors to bind target molecules.

    What is exocytosis?

    Movement of molecules out of the cell via vesicles.

    What is the apical membrane?

    Surface of an epithelial cell facing a fluid-filled chamber.

    What is the basolateral membrane?

    Surface of an epithelial cell adjacent to blood vessels.

    What is the transcellular pathway?

    Movement through an epithelial cell from one membrane to another.

    What is the paracellular pathway?

    Diffusion between adjacent epithelial cells.

    What are tight junctions?

    Seals between epithelial cells limiting paracellular diffusion.