Gateway to the CellGateway to the Cell

The cell membrane is flexibleflexible and allows a unicellular organism to move

Protective barrierProtective barrier

Regulate transport in & out Regulate transport in & out of cell of cell (selectively (selectively permeable)permeable)

Allow cell recognitionAllow cell recognition

Provide anchoring sites for Provide anchoring sites for filaments of cytoskeletonfilaments of cytoskeleton

Provide a binding site for Provide a binding site for enzymesenzymes

Interlocking surfaces bind Interlocking surfaces bind cells cells together (junctions)together (junctions)

Contains the cytoplasm Contains the cytoplasm (fluid in cell) (fluid in cell)

Phospholipids ProteinsPhospholipids Proteins (Integral & Peripheral) (Integral & Peripheral)

Cholesterol Carbohydrates Cholesterol Carbohydrates (glucose)(glucose)

Diffusion of water across a membrane

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

Doesn’t require energy

Simple DiffusionSimple Diffusion

Doesn’tDoesn’t require require energyenergy

Moves Moves high to lowhigh to low concentrationconcentration Example: Example: OxygenOxygen diffusing into a cell diffusing into a cell and and carbon dioxidecarbon dioxide diffusing outdiffusing out

Facilitated diffusion

Doesn’t require energy

Uses transport proteins to move high to low concentration

Examples: Examples: GlucoseGlucose or or amino acidsamino acids moving moving from blood into a from blood into a cell.cell.

Channel proteins are embedded in the cell membrane & have a pore for materials to cross

Carrier proteins can change shape to move material from one side of the membrane to the other

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

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

They They bond and bond and drag drag moleculesmolecules through through the lipid bilayer the lipid bilayer and release them and release them on the opposite on the opposite side.side.

Other carrier Other carrier proteins proteins change shapechange shape to move to move materials materials across the across the cell cell membranemembrane

Requires energy or ATP

Moves materials from LOW to HIGH concentration

AGAINST concentration gradient

Examples: Pumping Na+ (sodium ions) out and K+ (potassium ions) in against strong concentration gradients.

Called Na+-K+ Pump

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

Endocytosis- moving things in.

Cells absorb molecules by engulfing them.

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

ExocytosiExocytosiss- moving

things out.

Molecules are Molecules are moved outmoved out of the cell by of the cell by vesiclesvesicles that that fusefuse with with the plasma membrane.the plasma membrane. This is how many This is how many hormoneshormones are secreted and how are secreted and how nerve cellsnerve cells communicate with one anothercommunicate with one another.

Exocytic vesicle Exocytic vesicle immediately after immediately after fusion with plasma fusion with plasma membrane.membrane.