Homeostasis and Transport across membranes

Ch5 p94

Types of TransportPassive Transport

DiffusionOsmosisFacilitated diffusion

Active TransportCell membrane

pumpsEndocytosisExocytosis

Movement across a membrane depends on BOTH the concentrations of particles AND their size, shape and if they dissolve in lipids!

Passive TransportDiffusion – the movement of particles from

an area of high concentration to an area of low concentrationMovement down its concentration gradientHappens naturally due to kinetic energy of

molecules Dye in a glass of water (where would it happen

faster – hot water or cold water?)

Movement of particles happens until EQUILIBRIUM is reached as long as the particles…

…can move thru the substance or across the membrane

Passive TransportOsmosis – the

movement of WATER from an area of high concentration to low concentrationHypertonic: get your

energy OUTHypotonic: Hypo the

HippoIsotonic: equal

http://www.youtube.com/watch?v=kkPiRT2ewVA&feature=related http://www.youtube.com/watch?v=iG6Dd3COug4&NR=1

Passive TransportFacilitated Diffusion – the movement of

particles is assisted by carrier proteins in the cell membrane.

Active TransportCell Membrane pumps

Sodium (Na)-potassium (K) pumps“Na Na NAAA Na, Na Na NAAA Na HEY HEY

Good bye”Our cells need the potassium in them. It

doesn’t care if there isn’t a lot outside the cell, it just wants to bring in as much as it can.

Sodium sneaks in the cell, and isn’t needed. SO…the cell uses energy to kick out the Na and bring in the K

Active Transport

Active TransportEndocytosis: endo=in cyto=cell

Pinocytosis “to drink” brings in fluidPhagocytosis “to eat” brings in large particles

or cellsThe cell membrane forms a divit and wraps

around until it connects on the other side, forming a vessicle.

Active TransportExocytosis: Exo=exit cyto=cell

When a vesicle that has formed in the cell, attaches to the cell membrane and opens up, releasing its contents out of the cell.

http://www.youtube.com/watch?v=4gLtk8Yc1Zc