AP BIO UNIT 2 - Cell Transport

easily passes across the plasma membrane

nonpolar, hydrophobic, small molecules

aquaporins

water-specific channels

facilitated transport

substances must pass through channel proteins due bc it is hydrophilic or charged, no energy required, at equalibrium

passive transport

high to low

active transport

low to high, requires ATP

ion pumps

membrane potential = voltage difference across a membrane

electrogenic pump

protein that generates voltage across a membrane

sodium-potassium pump

pumps out 3 Na+ ions and brings in two K+, depends on ATP

cotransport

occurs when active transport of a solute indirectly drives transport of other solutes

primary active transport

directly uses atp to transport something

secondary active transport

occurs when a substance is moved across its concentration gradient by using the energy captured from the movement of another substance passively moving along its concentration gradient

osmosis

water is diffused

water always moves from areas

where it is more concentrated to where it is less concentrated

tonicity

describes osmotic gradients

isotonic

equal on both sides

hypotonic

cell loses water

hypertonic

cell gains water

plant cell in a hypertonic solution

cell wall becomes turgid

animal cell in a hypertonic solution

bursts, cell membrane is not strong enough

water potenital

how readily water flows from high to low

endocytosis

when a large particle wants to enter the cell and cannot thru a protein, it is engulfed by the cell

pinocytosis

ingests liquids

phagocytosis

ingests solids

receptor mediated endocystosis

receptor proteins on the cell surface are used to capture a specific target molecule.

exocytosis

large particles sent outside of the cell

antiporter

carries 2 ions/molecules in different directions

symporter

carries 2 ions/molecules in same direction