Physiology 261 Lab: Membrane Dynamics and Osmosis (Week 1)

Vocabulary flashcards covering key concepts from membrane dynamics, osmosis, diffusion, and membrane transport.

Osmosis

Movement of water across a selectively permeable membrane toward higher solute concentration, often via aquaporins.

Osmotic pressure

The pressure required to prevent water movement by osmosis; the force driving water movement across a membrane.

Osmolarity

The number of osmotically active particles per liter of solution; used to compare solutions.

Osmolarity vs osmolality

Osmolarity is per liter of solution; osmolality is per kilogram of solvent; in physiology they are practically interchangeable.

Isosmotic

Having the same osmolarity as another solution.

Isotonic

A solution that causes no net water movement across a cell membrane because its effective osmolarity matches that of the cytosol.

Hyperosmotic

A solution with higher osmolarity than another, leading to water movement out of cells.

Hyposmotic

A solution with lower osmolarity than another, leading to water movement into cells.

Tonicity

Describes the effect of a solution on cell volume, determined by nonpenetrating solute concentrations.

Diffusion

Passive movement of molecules from high to low concentration down a concentration gradient; no energy required.

Simple diffusion

Diffusion of lipid-soluble or small uncharged molecules directly through the lipid bilayer.

Facilitated diffusion

Diffusion via membrane proteins down its concentration gradient; uses channels or carriers and requires no energy.

Channel-mediated diffusion

Diffusion through membrane channels (ion channels or aquaporins) down a gradient.

Carrier-mediated transport

Transport of substances via membrane carrier proteins; exhibits specificity, saturation, and sometimes competition.

Ion channel

Protein pore in a cell membrane that allows selective passage of ions; can be leak or gated.

Aquaporin

Water-selective channel protein that facilitates osmosis.

Primary active transport

Energy-dependent transport that uses direct ATP hydrolysis to move substances against their gradients.

Na+-K+-ATPase

Sodium-potassium pump; uses ATP to pump Na+ out and K+ in, maintaining gradients and resting potential.

Secondary active transport

Transport that uses the gradient of one molecule to drive uphill transport of another; indirect energy source.

Symport

Cotransport where two substrates move in the same direction across a membrane.

Antiport

Cotransport where two substrates move in opposite directions across a membrane.

Endocytosis

Cellular uptake of material via vesicle formation; energy-dependent, can be receptor-mediated.

Exocytosis

Release of vesicle contents to the extracellular space; involves vesicular docking and fusion.

Phagocytosis

Endocytosis of large particles via cytoskeletal rearrangements to form phagosomes.

Transcytosis

Transport across an epithelium via endocytosis, vesicular transport, and exocytosis.

Resting membrane potential

The steady membrane potential of a cell at rest, typically negative inside and largely determined by K+ permeability.