The Cell The Cell Membrane Membrane

and and MovementMovement

s of s of MoleculesMolecules

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

Water

Plasma Membrane

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)

Question: What surrounds each side of the cell membrane?

Answer: Water based fluids.

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.

Mosaic StructuresProteins

embedded in the phospholipid bilayer used for transport

Other Membrane StructuresCholesterol- makes the membrane

less permeable and maintains flexability

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”

SolutionSolution

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.

Types of Solutions IsoIsotonic Solutiontonic Solution::

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::

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!

Types of Solutions HyperHypertonic Solutiontonic Solution: :

osmosis

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

Comparison of Hypo, Iso, and Hypertonic Solutions

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

Explain

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)

Endocytosis and Exocytosis

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:

Directions:Directions:

1. Draw & Complete the following Venn Diagram:1. Draw & Complete the following Venn Diagram:

PASSIVEACTIVE