AP Bio 2.5-2.7

concentration gradient

difference in the concentration of a substance on one side of the membrane compared to the other

passive transport

• no energy used

• materials move down concentration gradient

  • mols more likely to bump into each other & cross the membrane

simple diffusion

small nonpolar molecules move directly through the phospholipid bilayer

• passive

facilitated diffusion

large polar molecules or ions require a protein channel to pass through the membrane

• passive

aquaporins

move large quantities of water

• facilitated

• water can pass through membrane in small quantities this just increases amount

net mvmt

overall mvmt of materials

• passive transport - net movement from high to low

• active transport - net mvmt from low to high (mostly)

active transport

requires E to move molecules w/ a protein pump often against concentration gradient

active transport lets cells

set up & maintain concentration gradients of solutes across a membrane

vesicular transport

• endocytosis & exocytosis

• active transport

• move large substances into & out of cells

osmosis

mvmt of water through a semipermeable membrane

solutions

made of solvent & solutes

hypertonic

more

isotonic

same

hypotonic

less

direction of water mvmt

towards the area of higher solute concentration→ balance

AKA high H₂O potential → low H₂O potential

hyper H₂O mvmt

out

iso  H₂O mvmt

both ways

hypo  H₂O mvmt

in

plant cells require

hypotonic environment to maintain turgor pressure

• animal cell would burst but plant cells have cell walls = they’re safe

osmoregulation

organism’s ability to control their internal solute composition to maintain H₂O balance

water potential

measure of how freely H₂O molecules can move in a solution

solute potential

-iCRT

i=how many a molecule splits into in water

c=molar concentration

r=0.0831 (pressure constant)

t=temp (K)

water potential =

pressure potential + solute potential

• pressure potential always 0 in an open beaker