Osmosis, Osmosis, Diffusion, Diffusion,

Active Transport Active Transport

Diffusion, Osmosis and Diffusion, Osmosis and Concentration GradientConcentration Gradient

Diffusion – the movement of a substance Diffusion – the movement of a substance from a high concentration to a low from a high concentration to a low concentrationconcentration

Osmosis – the movement of WATER from a Osmosis – the movement of WATER from a high concentration to a low concentration.high concentration to a low concentration.

Concentration Gradient – the difference in Concentration Gradient – the difference in concentration between a region of high concentration between a region of high concentration and a region of lower concentration and a region of lower concentrationconcentration

Passive or Active Transport:Passive or Active Transport: Passive Transport - does not Passive Transport - does not

require cell energy require cell energy Examples: Diffusion, Facilitated Examples: Diffusion, Facilitated

diffusion and Osmosis  diffusion and Osmosis   Active Transport Requires cell Active Transport Requires cell

energy (ATP) energy (ATP) Examples: Carrier mediated active Examples: Carrier mediated active

transport, Endocytosis and transport, Endocytosis and ExocytosisExocytosis

Methods of Transport:Methods of Transport: 1. Diffusion:1. Diffusion: the random movement the random movement

of particles of a solute from an area of particles of a solute from an area of higher concentration to an area of of higher concentration to an area of lower concentration.lower concentration. Particles always move Particles always move withwith (down) a (down) a

concentrationconcentration gradientgradient (the (the difference in concentrations across a difference in concentrations across a membrane).membrane).

Passive transport.Passive transport.

EquilibriumEquilibrium Diffusion stops at Diffusion stops at equilibriumequilibrium (when the (when the

concentrations across a membrane are equal).concentrations across a membrane are equal). The movement of molecules continues at The movement of molecules continues at

equilibrium but the # of molecules moving equilibrium but the # of molecules moving across the membrane remains the same.across the membrane remains the same.

The rate of transport is dependent on: The rate of transport is dependent on: 1) if the material is solid, liquid or gas.1) if the material is solid, liquid or gas. 2) the size of the molecules.2) the size of the molecules. 3) temperature3) temperature

Examples of molecules that can diffuse through Examples of molecules that can diffuse through the bilayer: carbon dioxide, oxygen, water but the bilayer: carbon dioxide, oxygen, water but very, very slowly.very, very slowly.

Diffusion through a Plasma Diffusion through a Plasma MembraneMembrane

OsmosisOsmosis Osmosis:Osmosis: the diffusion of water the diffusion of water

through a selectively permeable through a selectively permeable membrane.membrane. Passive transportPassive transport Water molecules move from a higher Water molecules move from a higher

concentration OF WATER to a lower concentration OF WATER to a lower concentration OF WATER.concentration OF WATER.

Water will move to where there is a Water will move to where there is a greater amount of solute because there is greater amount of solute because there is less water there less water there

Isotonic SolutionIsotonic Solution Isotonic solutions:Isotonic solutions: the the

concentration of solute concentration of solute inside and outside of the inside and outside of the cell is the same.cell is the same.

Isotonic:Isotonic: Water in = Water outWater in = Water out No net movement of No net movement of

water.water. Molecules in Molecules in

equilibrium.equilibrium. Normal state for animal Normal state for animal

cells.cells. Cell in homeostasis.Cell in homeostasis.

Hypotonic SolutionHypotonic Solution Hypotonic solutions:Hypotonic solutions: the concentration the concentration

of solute is lower outside the cell than of solute is lower outside the cell than inside the cell. inside the cell. Have more water outside the cell so water Have more water outside the cell so water

moves into the cellmoves into the cell Causes an increase in pressure inside the cell: Causes an increase in pressure inside the cell:

called called turgor pressure (plants) or osmotic turgor pressure (plants) or osmotic pressure (animals).pressure (animals).

Increase in pressure in animal cells causes Increase in pressure in animal cells causes them to swell or even burst; gives plant cells them to swell or even burst; gives plant cells shape and support.shape and support.

Example Hypotonic Example Hypotonic Hypotonic:Hypotonic: Water enters Water enters

cell.cell. Cell swells and Cell swells and

bursts bursts (cytolysis).(cytolysis).

Give plant cells Give plant cells shape and shape and support.support.

Hypertonic SolutionHypertonic Solution Hypertonic solutions: the Hypertonic solutions: the

concentration of solute is higher concentration of solute is higher outside the cell than inside the cell.outside the cell than inside the cell. Have more water inside the cell so Have more water inside the cell so

water moves out of the cellwater moves out of the cell Causes a drop in turgor or osmotic Causes a drop in turgor or osmotic

pressure: called pressure: called plasmolysis.plasmolysis. Plasmolysis causes animal cells to Plasmolysis causes animal cells to

shrivel up and plants to wilt.shrivel up and plants to wilt.

Hypertonic Example Hypertonic Example Hypertonic:Hypertonic: Water exits cell.Water exits cell. Cell shrinks Cell shrinks

(plasmolysis) due (plasmolysis) due to    water loss.to    water loss.

The effects of osmotic The effects of osmotic pressurepressure

Hypo, Iso, HyperHypo, Iso, Hyper

The effects of osmotic The effects of osmotic pressure in a plant cell pressure in a plant cell

Facilitated DiffusionFacilitated Diffusion Particles always move Particles always move

withwith (down) a (down) a concentrationconcentration gradientgradient..

Uses transport/channel Uses transport/channel proteins.proteins.

Passive transport.Passive transport. Usually for specific Usually for specific

molecules such as molecules such as glucose.glucose.

Facilitated diffusion Facilitated diffusion stops at stops at equilibriumequilibrium..

Active transportActive transport Active Transport:Active Transport: requires energy in the requires energy in the

form of ATP.form of ATP. Capable of moving solute particles against the Capable of moving solute particles against the

conc. gradient (from low conc. to high conc.)conc. gradient (from low conc. to high conc.) Uses transport/carrier proteins (protein Uses transport/carrier proteins (protein

pumps) embedded in the plasma membrane.pumps) embedded in the plasma membrane. Carrier proteins are specific for the molecules Carrier proteins are specific for the molecules

that they allow through. The carrier protein that they allow through. The carrier protein changes shape which requires energy (ATP). changes shape which requires energy (ATP).

Active Transport against Active Transport against the concentration gradientthe concentration gradient

Active Transport Active Transport Endocytosis:Endocytosis: a process of taking a process of taking

material into the cell by means of material into the cell by means of infoldings, or pockets, of the cell infoldings, or pockets, of the cell membrane (usually putting them into a membrane (usually putting them into a vacuole).vacuole). Phagocytosis -“Cell eating”Phagocytosis -“Cell eating”

Nonspecific moleculesNonspecific molecules Intake of solidsIntake of solids

Pinocytosis –”Cell Drinking”Pinocytosis –”Cell Drinking” Nonspecific moleculesNonspecific molecules Intake of small droplets of liquidIntake of small droplets of liquid

Active Transport Active Transport Exocytosis (reverse endocytosis):Exocytosis (reverse endocytosis):

a process in which the membrane of a process in which the membrane of the vacuole surrounding the material the vacuole surrounding the material fuses with the cell membrane, fuses with the cell membrane, forcing the contents out of the cell.forcing the contents out of the cell.

EXO and ENDOEXO and ENDO