The Cell (Plasma) The Cell (Plasma) Membrane Membrane

Gateway to the CellGateway to the Cell

Functions of Cell Functions of Cell MembraneMembrane1. Protective barrierProtective barrier

2.2. Regulates transport in & out of Regulates transport in & out of cell cell (selectively permeable)(selectively permeable)

3.3. Allows cell recognitionAllows cell recognition

4.4. Maintain ion concentrationMaintain ion concentration

Cell MembraneCell Membrane

The cell The cell membrane is membrane is flexibleflexible and and allows a allows a unicellularunicellular organism to organism to movemove

HomeostasisHomeostasis

•BalancedBalanced internal condition internal condition of cellsof cells

•Also calledAlso called equilibriumequilibrium

•Maintained by plasma Maintained by plasma membranemembrane controlling what controlling what enters & leaves the cellenters & leaves the cell

Structure of the Structure of the Cell MembraneCell Membrane

Polar heads are hydrophilichydrophilic “water loving”Nonpolar tails are hydrophobichydrophobic “water fearing”

Cell MembraneCell Membrane

Makes membrane “Selective” in what crosses

Phospholipid Bilayer

Fluid Mosaic Model(Lots of different types of molecules that assemble to form a function)

Cell MembraneCell Membrane

Hydrophobic molecules pass easily; hydrophillic DO NOT

The cell membrane is made of 2 layers of phospholipidphospholipids called the lipid bilayerbilayer

Small molecules and larger hydrophobic molecules move through easily.e.g. O2, CO2, H2O

Semipermeable Semipermeable MembraneMembrane

Ions, hydrophilic molecules larger than water, and large protein molecules do not move through the membrane on their own.

Semipermeable Semipermeable MembraneMembrane

SolutionsSolutions

• Solutions are made of solute Solutions are made of solute and a solventand a solvent

• SolventSolvent – The liquid part. It – The liquid part. It does the dissolving. does the dissolving.

• SoluteSolute – The thing being – The thing being dissolved. Salt and sugar are dissolved. Salt and sugar are solutes.solutes.

Types of Transport Types of Transport Across Cell Across Cell MembranesMembranes1. Diffusion2. Osmosis3. Facilitated

Diffusion4. Active Transport

DiffusionDiffusion

•Requires Requires NONO energyenergy

•Solutes move Solutes move from area of from area of HIGH to LOWHIGH to LOW concentratioconcentrationn

Diffusion: Draw this

Diffusion of LiquidsDiffusion of Liquids

Diffusion through a Diffusion through a MembraneMembrane

Cell membrane

Solute moves DOWN concentration gradient (HIGH to LOW)

OsmosisOsmosis

• Diffusion of Diffusion of waterwater across a across a membranemembrane

• Moves from Moves from HIGH HIGH water potentialwater potential (low solute) to (low solute) to LOW water LOW water potentialpotential (high (high solute)solute)

Diffusion across a membrane

Semipermeable

membrane

Diffusion of HDiffusion of H22O Across O Across A MembraneA Membrane

High H2O potentialLow solute concentration

Low H2O potentialHigh solute concentration

Osmosis: Draw this

Types of SolutionsTypes of Solutions

• Hypotonic Hypotonic – concentration of – concentration of solute is higher INSIDE the cell.solute is higher INSIDE the cell.

• Hypertonic Hypertonic – concentration of – concentration of solute is higher OUTSIDE the solute is higher OUTSIDE the cell.cell.

• Isotonic Isotonic – concentrations of – concentrations of solutes is the same inside and solutes is the same inside and outside the celloutside the cell

Plant and Animal Cells put into various solutions

Facilitated Facilitated DiffusionDiffusion

Doesn’t require energy

Uses transport proteins to move high to low concentrationExamples: Examples: GlucoseGlucose or or amino acidsamino acids moving moving from blood into a from blood into a cell.cell.

Proteins Are Critical to Proteins Are Critical to Membrane FunctionMembrane Function

Facilitated DiffusionFacilitated Diffusion

Molecules will randomly move Molecules will randomly move through the through the porespores in in Channel Channel ProteinsProteins..

Facilitated DiffusionFacilitated Diffusion• SomeSome Carrier Carrier

proteinsproteins do not do not extend through the extend through the membrane.membrane.

• They They bond and bond and drag moleculesdrag molecules through the lipid through the lipid bilayer and release bilayer and release them on the them on the opposite side.opposite side.

Three Forms of Transport Across the MembraneThree Forms of Transport Across the Membrane

Active TransportActive Transport

Requires energy or ATP

Moves materials from LOW to HIGH concentration

AGAINST concentration gradient

Sodium-Potassium Sodium-Potassium PumpPump

3 Na+ pumped in for every 2 K+ pumped out; creates a membrane

potential

Think/Pair/ShareThink/Pair/Share

•Work with a partner Work with a partner to create different to create different situations that can situations that can be classified as be classified as diffusion.diffusion.

•Do the same for Do the same for osmosis.osmosis.