Chapter 5Chapter 5
The Plasma MembraneThe Plasma Membrane
The Cell Membrane:The Cell Membrane:
OUTSIDE
INSIDE
HYDROPHILIC HEAD
HYDROPHOBIC TAIL
TRANSPORT PROTEIN
The cell membrane is referred toas a PHOSPHOLIPID BILAYER
The Plasma MembraneThe Plasma Membrane
It contains two layers of phospholipidsIt contains two layers of phospholipids
The hydrophobic (water-hating) tails face eachother like peanut butter and jelly.The hydrophobic (water-hating) tails face eachother like peanut butter and jelly.
The hydrophilic heads face the watery exteriorsof the bilayerThe hydrophilic heads face the watery exteriorsof the bilayer
Sometimes fats, proteins, and othercarbohydrate molecules float around the bilayerlike ice cubes in water. They are not stationary.Sometimes fats, proteins, and othercarbohydrate molecules float around the bilayerlike ice cubes in water. They are not stationary.
A Gallery of Membrane ProteinsA Gallery of Membrane Proteins
Passive transporters- channels that allowspecific thing to enter the cell withoutinputting energy.Passive transporters- channels that allowspecific thing to enter the cell withoutinputting energy.
A Gallery of Membrane ProteinsA Gallery of Membrane Proteins
Active Transporters- channels that allowspecific thing to enter the cell with theinput of energy (ATP)Active Transporters- channels that allowspecific thing to enter the cell with theinput of energy (ATP)
DiffusionDiffusion
Diffusion: The movement of molecules toan area of high concentration [] to anarea of low concentration [] until theconcentration is the same everywhere.Diffusion: The movement of molecules toan area of high concentration [] to anarea of low concentration [] until theconcentration is the same everywhere.
OsmosisOsmosis
Water may constantly pass into and out ofcells through these plasma membranes(lipid bilayers). This uninterrupted flow ofwater through these membranes is calledOSMOSIS.Water may constantly pass into and out ofcells through these plasma membranes(lipid bilayers). This uninterrupted flow ofwater through these membranes is calledOSMOSIS.
Water has the free pass to travel in andout of organisms and cells. So water iscalled a solvent.Water has the free pass to travel in andout of organisms and cells. So water iscalled a solvent.
Why do I “melt” when salt is pouredon me?
Because wateralways goes towhere there ismore “stuff”
HypotonicHypotonic
Hypotonic- having a lower concentrationof solutesHypotonic- having a lower concentrationof solutes
HypertonicHypertonic
Hypertonic- having a higher concentrationof solutesHypertonic- having a higher concentrationof solutes
What about fish?What about fish?
Do either of these fish need to “drink” the water
to survive?
Who will it be?
We drink the waterbecause there ismore “stuff” in theocean than in us.Therefore, we mustdrink the water torecover the waterwe lose to osmosis.
Other Transport MechanismsOther Transport Mechanisms
Membranes are selectively permeable --(they only let specific stuff pass to the other side)Membranes are selectively permeable --(they only let specific stuff pass to the other side)
Passive TransportPassive Transport
Substances move DOWN theirconcentration gradient into or out of thecell (a person going down a water slide)Substances move DOWN theirconcentration gradient into or out of thecell (a person going down a water slide)
No extra energy is required to performpassive transport.No extra energy is required to performpassive transport.
Active TransportActive Transport
Substances move through transportproteins but AGAINST the concentrationgradient. Cells use free energy (usuallyfrom ATP) to do this. It requires extraenergy.Substances move through transportproteins but AGAINST the concentrationgradient. Cells use free energy (usuallyfrom ATP) to do this. It requires extraenergy.
