Cell MembraneCell Membrane

Cell membraneCell membraneA gateway and a barrier for the cell. A gateway and a barrier for the cell.

Controls what enters & exitsControls what enters & exits

composed of phospholipids and composed of phospholipids and proteins. proteins.

PhospholipidsPhospholipids

Made up of a polar Made up of a polar head and a head and a nonpolar tail.nonpolar tail.

HeadHead – water – water lovingloving

Tails Tails – water hating– water hating Tails stay to inside Tails stay to inside

of bi-layer to avoid of bi-layer to avoid contact with water.contact with water.

Polar

Nonpolar

Lipid Bilayer:

ProteinsProteins

Marker ProteinsMarker Proteins – attach to – attach to carbohydrates on cell surface carbohydrates on cell surface that identifies cell type.that identifies cell type.

Receptor ProteinsReceptor Proteins – recognize – recognize and bind to specific and bind to specific substances outside the cellsubstances outside the cell

Transport ProteinsTransport Proteins –helps –helps substances move across the substances move across the membrane.membrane.

OsmosisOsmosis diffusion of diffusion of waterwater across cell membranes across cell membranes NO ENERGY REQUIREDNO ENERGY REQUIRED Ex: lysing of a blood cell.Ex: lysing of a blood cell.

DiffusionDiffusionnet movement of molecules from a net movement of molecules from a

region of region of highhigh concentration concentration toto a a region of region of lowerlower concentration concentration

With the With the “concentration gradient”“concentration gradient”NO ENERGY REQUIREDNO ENERGY REQUIREDEx: perfumes from a Ex: perfumes from a

bouquet spreads bouquet spreads

across roomacross room

Facilitated DiffusionFacilitated Diffusion the diffusion of a substance moving with the diffusion of a substance moving with

the concentration gradient, but which the concentration gradient, but which require the assistance of other require the assistance of other molecules.molecules.

NO ENERGY REQUIREDNO ENERGY REQUIRED The “facilitation” is The “facilitation” is physically turningphysically turning a a

molecule so that it may more easily pass molecule so that it may more easily pass through a membrane through a membrane

Active TransportActive Transportmovement of molecules from a region movement of molecules from a region

of of lowlow concentration concentration toto a region of a region of highhigh concentration.concentration.

This is against the “concentration This is against the “concentration gradient”gradient”

Requires Requires

ENERGYENERGY!!!!!!

Two main types of active Two main types of active transporttransport

movement directly across the cell membrane movement directly across the cell membrane with assistance from with assistance from transport proteinstransport proteins

EX: EX: sodium-potassium pumpsodium-potassium pump helps nerve cells to pass their signals in the helps nerve cells to pass their signals in the

form of electrical impulses form of electrical impulses maintain a higher concentration of maintain a higher concentration of

potassium ions inside the cells compared to potassium ions inside the cells compared to outside, and a higher concentration of outside, and a higher concentration of sodium ions outside of cells compared to sodium ions outside of cells compared to insideinside

Sodium potassium pumpSodium potassium pump

Two main types of active Two main types of active transporttransport

endocytosisendocytosis - is an infolding and then - is an infolding and then pinching in of the cell membrane so that pinching in of the cell membrane so that materials are engulfed into a vacuole or materials are engulfed into a vacuole or vesicle within the cell vesicle within the cell PhagocytosisPhagocytosis solid particles taken into the solid particles taken into the

cellcell

Two main types of active Two main types of active transporttransport

ExocytosisExocytosis – substances are released – substances are released from the cell through a vesicle that from the cell through a vesicle that transports the substance to the cell transports the substance to the cell surface and then fuses with the surface and then fuses with the membrane to let the substance out membrane to let the substance out of the cell. of the cell.