Transport AP Bio Quiz

Gradient

Difference in concentration between two areas

Concentration Gradient

Difference between high and low concentration

Passive Transport

Movement across membrane without ATP; high → low

Active Transport

Movement across membrane using ATP; low → high

Simple Diffusion

Small nonpolar molecules move directly through membrane; high → low; no ATP

Simple Diffusion Examples

O2, CO2, small nonpolar molecules

Facilitated Diffusion

Molecules move through a membrane protein; high → low; no ATP

Facilitated Diffusion Examples

Glucose, Na+, K+, Ca2+, and other polar molecules

Osmosis

Diffusion of water across a selectively permeable membrane

Aquaporin

Protein channel that allows water to cross the membrane

Endocytosis

Brings substances INTO the cell using a vesicle

Exocytosis

Sends substances OUT of the cell using a vesicle

Membrane Transporter

Protein that helps substances cross the cell membrane

Voltage-Gated Ion Channel

Channel that opens when a certain voltage or charge is reached

Antiporter

Two substances move in opposite directions; one in, one out

Symporter

Two substances move in the same direction

Sodium-Potassium Pump

Uses ATP to move 3 Na+ out and 2 K+ into the cell; low → high

Electrochemical Gradient

Combination of a concentration gradient and electrical charge difference caused by ions

Selective Permeability

Membrane allows some substances to cross but blocks others