lecture 2: membranes, diffusion, osmosis Flashcards
function of membranes
- regulate the passage of substances into and out of cells and between cell organelle and cytosol
- detect chemical messengers arriving at the cell surface
- link adjacent cells together by membrane junctions
- anchor cell sto the extracellular matrix
phospholipid bilayer
- hydrophilic heads
- hydrophobic tails
desmosome function
strong attachment
tight junction function
- form a barrier
- link neighborning cells, for integrity
gap junction function
allow ions and some other molecules to pass, allow for communication between neighboring cells
chemical properties that determine whether a solute can diffuse through the membrane
- molecular weight: small
- surface area: larger area
- membrane permeability
- nonpolar can diffuse
facilitated diffusion
substances move down concentration gradient (no energy required)
active transport
substances move up conentration gradient (energy required)
primary active transport
pumps that use ATP
secondary active transport
uses the energy of an existing gradient
* energy of Na+ gradient is used
cotransport
the ion and the second solute cross the membrane in the same direction
countertransport
the ion and the second solute move in opposite directions
one pump cycle of Na+/K+ pump
3 Na+ out
2 K+ in
One ATP used
depletion of a cells ATP stores could result in
- decreased primary active transport
- decreased secondary active transport
- alteration in cell membrane potential
osmosis
movement of water into and out of cells
* through aquaporins
