Plasma membrane/cell membraneHow does it control what goes into and outof the cell????

Selectively permeable:

Allows only certain molecules to pass through

Permeable: Can pass through

BUT

Not all molecules get in the same way!

Selective Permeability

O2, CO2, and other small, nonpolar

molecules; some water molecules

glucose and other large, polar, water-soluable molecules; ions,

water molecules

Nonpolar= equal charge throughout molecule Polar= uneven charge in molecule

Active (requires NRG)

Passive (no NRG)

Types of Transport

NRG= ENERGY

• Whether passive or active transport is Whether passive or active transport is needed depends on the needed depends on the CONCENTRATION GRADIENTCONCENTRATION GRADIENT

• The concentration gradient is the The concentration gradient is the differencedifference in the concentration of a in the concentration of a substance in two different spacessubstance in two different spaces

• ConcentrationConcentration - the amount of a - the amount of a particular substance in a contained particular substance in a contained area compared with the amount of the area compared with the amount of the same substance in another areasame substance in another area

• Translation: Amount of something in a Translation: Amount of something in a space (water, salt, sugar, iron,)space (water, salt, sugar, iron,)

Passive transport:

Active transport:

No energy needed

Follows concentration gradient (high to low)

Energy needed

Against concentration gradient:

Transport within the cellTransport within the cell

Low to high

(Adenosine triphosphate)

Osmosis

Passive

Passive Transport

Diffusion

Facilitated Diffusion

Pass

ive

Tra

nspo

rt

High Concentration

Low Concentration

High Concentration Low

Concentration

DiffusionPassive Transport

H L

Movement of SUBSTANCE from area of high concentration to area of low concentration

Equilibrium reached when molecules are evenly distributed

“out”

Passive transport

Factors Affecting Diffusion Rate

• Steepness of concentration gradient– Steeper gradient, faster diffusion

• Molecular size– Smaller molecules, faster diffusion

• Temperature– Higher temperature, faster diffusion

• Charge– Charged molecules cannot diffuse (NaCl Na+ Cl-)

HighConcentration

LowConcentration

CellMembrane

Glucosemolecules

Proteinchannel

Facilitated Diffusion

Protein channel recognizes molecule and allows entry

No NRG required, following concentration gradient

Faster than diffusion

Osmosis

Diffusion of WATER across a membrane

100 ml Distilled

H20

100 ml10% Saltsolution

Which has more water?

Water will move into or out of cell following the concentration gradient of water

Osmosis

Where is there more water???

Osmosis in ANIMAL CELLS

• In Pure water • In STRONG Sugar solution

WEAK sugar/salt solution INSIDE

animal cell

Cell swells & ... Cell swells & ... LYSE LYSE (BURST) (BURST)

WEAK sugar/salt

solution INSIDE animal cell

Cell shrinksCell shrinks

Osmosis in PLANT CELLS

• In Pure water • In STRONG Sugar solution

WEAK sugar/salt solution INSIDE

potato cell

Cell swells : Cell swells : TURGIDTURGID

WEAK sugar/salt solution INSIDE

potato cell

Cell shrinks : Cell shrinks : PLASMOLYSEDPLASMOLYSED

Plasmolysis

http://www.uic.edu/classes/bios/bios100/lectf03am/plasmolysis.jpg

Plasmolysis video site

Cell Size

How does the size of a cell affect the rate of exchange of materials in and out of the cell?

The bigger the surface area of the cell membrane, the more materials can diffuse in and out of the cell.

MembraneMovements

Active

Active Transport

Pumps

Endocytosis Exyocytosis

Against concentrationgradient

Uses NRG (ATP)

Active T

ransportHigh Concentration

Low Concentration

Active TransportActive Transport

LC HC

• Span the lipid bilayer

• Interior is able to open to both sides

• Change shape when they interact with solute

• Move water-soluble substances across a membrane

Transport Proteins

Pumps

MembraneMovements

Endocytosis and Exocytosis

plasma membrane

cytoplasm

cytoplasm

Exocytosis

Endocytosis

Exocytosis

Pinocytosis (cell drinking)

Phagocytosis (cell eating)

Process where cell membrane “pinches in” drawing molecules into the cell forming a pinocytic vesicle

Process where pseudopods of a cell flow around matter and engulf it forming a food vacuole

Phagocytosis (Movie)

What about single celled organisms that live in freshwater (amoeba/paramecium)? Why don’t they burst?

Active Transport: going against the gradient

Passive Transport:Passive Transport:• Mvmt of materials Mvmt of materials

Without use of energy.Without use of energy.

• With Concentration With Concentration GradientGradient

• HCHCLCLC

• Examples:Examples:– DiffusionDiffusion– OsmosisOsmosis– Facilitated DiffusionFacilitated Diffusion

Active TransportActive Transport• Mvmt of materials Mvmt of materials using using

energy.energy.

• Against Concentration Against Concentration gradientgradient

• LCLCHCHC

• Examples:Examples:– EndocytosisEndocytosis

• PhagocytosisPhagocytosis• PinocytosisPinocytosis

– ExocytosisExocytosis

Video 4

• video segment.

Video 4

Active Transport

Animations

Dialysis Bag Experiment• http://ccollege.hccs.cc.tx.us/instru/Biology/AllStud

yPages/Diffusion_Osmosis/Baggif.swf

Elodea Cell• http://ccollege.hccs.cc.tx.us/instru/Biology/AllStud

yPages/Diffusion_Osmosis/Elodeagif.swf

Osmosis• http://ull.chemistry.uakron.edu/genobc/animation

s/osmosis.mov