The Plasma Membrane
The Plasma Membrane (aka cell membrane)
Boundary- protect and supportControls what enters and leaves
performing homeostasisHas selective permeability- the ability
to allow some molecules through the membrane -but not others
Fluid Mosaic ModelDescribes the movement and structure of the cell membrane
Fluid: Membrane is not solid but moves like a fluid
Mosaic: made of many different parts
Phospholipids are fluidPolar head- loves water2 Fatty acid tails- avoid waterHeads on outside, tails on inside
making a bilayer (2 layers)
The water loving “heads” The water loving “heads”
face the water.face the water.
The water hating “tails” The water hating “tails”
hide from the water. hide from the water.
This helps keep the integrity of the cell membrane This helps keep the integrity of the cell membrane (helps (helps keep it “glued” together”).keep it “glued” together”).
Small molecules can diffuse through the membrane (including Small molecules can diffuse through the membrane (including water).water).
Bigger molecules need proteins to help get in or out of the cell. Bigger molecules need proteins to help get in or out of the cell.
Other Membrane StructuresCarbohydrate Chains-glycoproteins
allow cells to recognize each other.Immune system
Molecular MovementsMolecules of liquids and gases are in
constant random motion bumping into each other
2 types of molecular movements- In and Out of Cells
1. Passive Transports: do not require energy
I. Diffusion
II. Osmosis
III. Facilitated Diffusion
2. Active Transports: require energy
I. Sodium Potassium Pump
II. Endocytosis
III. Exocytosis
Passive TransportsI. Simple Diffusion-net movement of
the same kind of molecule From an area of high
concentration to an area of low concentration- aka “down a concentration gradient”
Continues until the molecules are equally distributed
Passive TransportsSimple DiffusionMolecules pass straight through
phospholipid bilayerNo energy needed!!!
Diffusion
Passive TransportII. Osmosis (type of diffusion) –the diffusion
of water through a selectively permeable membrane From an area of high concentration to
an area of low concentration- aka “down a concentration gradient”
OsmosisOsmosisThe concentration of water in solution The concentration of water in solution
increases as the concentration of increases as the concentration of solutes decreasessolutes decreases
• 5% salt solution means ?% water5% salt solution means ?% water
•5% salt solution means 95% water5% salt solution means 95% water
•10% salt solution means ?% water10% salt solution means ?% water
•10% salt solution means 90% water10% salt solution means 90% water
Types of Solutions IsoIsotonic Solutiontonic Solution:: Concentration of Concentration of
solutes is thesolutes is the samesame inside and outside inside and outside the cell.the cell. Some water moves in, some water Some water moves in, some water
moves out.moves out. No net movement of water.No net movement of water. Cell remains the same.Cell remains the same.
Real World Applications IsoIsotonic Solutiontonic Solution::
Blood cells stored in isotonic plasma Blood cells stored in isotonic plasma solution for blood transfusionssolution for blood transfusions
HypoHypotonic Solutiontonic Solution: The : The concentration of solutes is concentration of solutes is lessless outside the cell than inside the cell.outside the cell than inside the cell. Net movement of water Net movement of water intointo the the
cell.cell. The cell will The cell will swellswell and may burst. and may burst. Ex: distilled water, pure water, Ex: distilled water, pure water,
pond waterpond water
Types of Solutions
HypoHypotonic Solutiontonic Solution::
A saltwater fish in freshwater tankA saltwater fish in freshwater tank Water intoxicationWater intoxication Milk of MagnesiaMilk of Magnesia
Real World Applications
Types of Solutions
HyperHypertonic Solutiontonic Solution: The : The concentration of solutes is concentration of solutes is moremore outside outside the cell than inside the cell. the cell than inside the cell. Net movement of water out of the Net movement of water out of the
cell.cell. Cell willCell will shrink shrink.. Ex: salt water, sea water, ocean Ex: salt water, sea water, ocean
waterwater
Salt sucks!Salt sucks!
Real world Application HyperHypertonic Solutiontonic Solution: :
Drinking salt water and dyingDrinking salt water and dying Gargling with salt water for sore throatGargling with salt water for sore throat Salt curing foodSalt curing food
osmosis
88% H2O 99% H2O
Which direction will the water flow?
Water always flows from high to low
Water (H2O)
25% H2O10% NaCl
Which direction will the water flow?
Change % NaCl to % water –osmosis is the movement of water through the plasma membrane
90% H2OWater (H2O)
90% H2O 80% H2O
Which direction will the water flow?
Water always flows from high to low
Water (H2O)
Osmotic Pressure in Plant Cells
Turgor PressureTurgor Pressure: The pressure in a : The pressure in a plant cell that results from water flowing plant cell that results from water flowing into the cell- maintaining central into the cell- maintaining central vacuole.vacuole. Gives plants the ability to stand up.Gives plants the ability to stand up.
Osmotic Pressure in Plant Cells With loss of turgor pressure central With loss of turgor pressure central
vacuole shrinks--plants wilt!vacuole shrinks--plants wilt!Plant cells require hypotonic situation to Plant cells require hypotonic situation to maintain turgor pressuremaintain turgor pressure
Passive Transport
III. Facilitated Diffusion
FacilitateFacilitate: to help or make easier: to help or make easier Molecules pass through a transport Molecules pass through a transport
protein because they are too big to fit protein because they are too big to fit through phospholipids ( EX: glucose)through phospholipids ( EX: glucose)
No energyNo energy needed needed Movement: Movement: high high concentration to concentration to lowlow Example: GlucoseExample: Glucose
Let’s review__________ transport does NOT require energy.__________ transport does NOT require energy.
Active transport DOES require ___________. Active transport DOES require ___________.
During passive transport, substances move from _______ to ______ During passive transport, substances move from _______ to ______ concentrations.concentrations.
____________ is the diffusion of water.____________ is the diffusion of water.
_________________ solutions could cause a cell to burst._________________ solutions could cause a cell to burst.
Facilitated diffusion uses proteins to allow ___________ and amino acids into or Facilitated diffusion uses proteins to allow ___________ and amino acids into or out of the cell.out of the cell.
Ion channels are proteins with special __________ that can open or close to let Ion channels are proteins with special __________ that can open or close to let _______ in or out._______ in or out.
Passive
energy
high low
Osmosis
Hypotonic
Sugars
gates
ions
Energy Requiring Transport Molecules move from an
area of low concentration to an area of high concentration.
“against the gradient”
Active TransportI. Sodium Potassium Pump Uses a proteinUses a protein EnergyEnergy is required is required To help maintain electrical signals in To help maintain electrical signals in
cellcell
active transport
Sodium Potassium PumpThe sodium potassium pump: A specialized protein that The sodium potassium pump: A specialized protein that
pumps 3 sodium ions (Napumps 3 sodium ions (Na++) out of the cell for every 2 ) out of the cell for every 2 potassium ions (Kpotassium ions (K++) that are moved into the cell.) that are moved into the cell.
Moves sodium and potassium against the concentration Moves sodium and potassium against the concentration gradient! (from low to high).gradient! (from low to high).
Sodium Potassium Pump
Sodium Potassium PumpSodium plays a key role in generating Sodium plays a key role in generating electrical electrical
signalssignals among our cells. If sodium builds up in our among our cells. If sodium builds up in our cells it can cause them to malfunction and can be cells it can cause them to malfunction and can be fatal.fatal.
Sodium is constantly “sneaking” back into our cells Sodium is constantly “sneaking” back into our cells after it is pumped out. after it is pumped out. How?How?
Ion channels (passive transport) allows them to Ion channels (passive transport) allows them to diffuse back into the cell diffuse back into the cell (with the concentration (with the concentration gradient).gradient).
II. Endocytosis A process in which cells surround and
engulf substances that are TOO BIG to enter the cell. The cell uses its own membrane to engulf the substance into a vesicle and bring it in.
Phagocytosis- cell eating
phagocytosisphagocytosis
III. Exocytosis Opposite endocytosis. When a cell Opposite endocytosis. When a cell
forms a vesicle around unwanted forms a vesicle around unwanted particles and expels it OUT of the cellparticles and expels it OUT of the cell
Endocytosis vs. Exocytosis
*Endo means “in”;
Exo means “out”.
*Cyto means cell
(Endocytosis= in cell;
Exocytosis= out of cell)
TransportTransport Type of TransportType of Transport Energy? Y/NEnergy? Y/N
Osmosis Osmosis (passive|active) energy required? ___(passive|active) energy required? ___
Endocytosis (passive|active) energy required? ___Endocytosis (passive|active) energy required? ___
Ion Channels (passive|active) energy required? __Ion Channels (passive|active) energy required? __
Facilitated Diffusion Facilitated Diffusion (passive|active) (passive|active) energy required? energy required? ______
ExocytosisExocytosis (passive|active) energy required? ___(passive|active) energy required? ___Sodium Potassium Pump Sodium Potassium Pump (passive|active) energy required? ___(passive|active) energy required? ___
N
Y
N
N
Y
Y
Low concentration
High concentration
ENER
GY
NO ENERGY A
CTI
VE
TRA
NSP
OR
TPA
SSIVE
TRAN
SPORT
Low concentration
Directions:1. Draw the following: