Passive TransportPassive Transport

Bell RingerBell Ringer

What is osmosis?What is osmosis?

ObjectivesObjectives

Relate Concentration Gradients, Relate Concentration Gradients, diffusion, and Equilibriumdiffusion, and Equilibrium

Predict the direction of water Predict the direction of water movement into and out of the cellsmovement into and out of the cells

Describe the importance of ion Describe the importance of ion channels in passive transportchannels in passive transport

Identify the role of carrier proteins Identify the role of carrier proteins in facilitated diffusion in facilitated diffusion

ChallengeChallenge

List at least two things that could List at least two things that could cause the movement of the dye in cause the movement of the dye in the beaker.the beaker.

ChallengeChallenge

What are you observing?What are you observing?

What process is at work?What process is at work?

Movement of particles in Movement of particles in CellsCells

Cells maintain Homeostasis by Cells maintain Homeostasis by controlling the movement of controlling the movement of substances across the cell substances across the cell membranemembrane

Movement in CellsMovement in Cells

Passive Transport – movement Passive Transport – movement across the cell membrane that does across the cell membrane that does not require energynot require energy

Concentration Gradient – Difference Concentration Gradient – Difference in the concentration of a substance in the concentration of a substance across a distance.across a distance.

EquilibriumEquilibrium

A condition which the concentration A condition which the concentration of a substance is equal throughout of a substance is equal throughout space.space.

ChallengeChallenge

For equilibrium to occur, what has For equilibrium to occur, what has to happen to the spheres in this to happen to the spheres in this picture?picture?

DiffusionDiffusion

Diffusion – the movement of Diffusion – the movement of particles from regions of high particles from regions of high density to regions of lower densitydensity to regions of lower density

Diffusion works quickly over short Diffusion works quickly over short distances, such as the dye moving distances, such as the dye moving through the beaker of water.through the beaker of water.

Diffusion Diffusion

Many substances enter and leave the Many substances enter and leave the cell through diffusion.cell through diffusion.

When substances cross the cell When substances cross the cell membrane they move “down” the membrane they move “down” the concentration gradient. They go concentration gradient. They go from an area of high concentration from an area of high concentration to an area of low concentrationto an area of low concentration

OsmosisOsmosis

Osmosis – the diffusion of water Osmosis – the diffusion of water through a selectively permeable through a selectively permeable membrane. Movement down the membrane. Movement down the concentration gradient.concentration gradient.

Osmosis is a type of passive Osmosis is a type of passive transporttransport

Direction of WaterDirection of Water

3 Types3 Types

HypertonicHypertonic

HypotonicHypotonic

IsotonicIsotonic

Hypertonic SolutionHypertonic Solution

The fluid outside the cell has a lower The fluid outside the cell has a lower free water concentration than the free water concentration than the cytosol, then the outside fluid is cytosol, then the outside fluid is hypertonic and water moves out of hypertonic and water moves out of the cellthe cell

HypotonicHypotonic

The fluid outside the cell has a The fluid outside the cell has a higher free water concentration than higher free water concentration than the cytosol, then the outside fluid is the cytosol, then the outside fluid is hypotonic and water moves into the hypotonic and water moves into the cellcell

IsotonicIsotonic

The fluid outside the cell has the The fluid outside the cell has the same free water concentration than same free water concentration than the cytosol, then the outside fluid is the cytosol, then the outside fluid is isotonic and water moves into and isotonic and water moves into and out of the cell at equal rates.out of the cell at equal rates.

Crossing the Cell Crossing the Cell MembraneMembrane

Transport Proteins called Channels Transport Proteins called Channels provide polar passageways through which provide polar passageways through which ions and polar molecules move across the ions and polar molecules move across the cell membrane.cell membrane.

Each channel only allows specific Each channel only allows specific substances to pass through the membranesubstances to pass through the membrane

Why is this important?Why is this important?

Diffusion through Ion Diffusion through Ion ChannelsChannels

SodiumSodium CalciumCalcium

Potassium Potassium ChlorideChloride

All are involved in many important All are involved in many important cell functionscell functions

IonsIons

Essential to the ability of nerve cells Essential to the ability of nerve cells to send electrical signals to send electrical signals

Movement of ions allows your heart Movement of ions allows your heart to beatto beat

Cross the cell membrane by Cross the cell membrane by diffusing through ion channels.diffusing through ion channels.

Ion ChannelIon Channel

Transport Protein with a polar pore Transport Protein with a polar pore through which ions can pass.through which ions can pass.

The pore spans the thickness of the The pore spans the thickness of the cell membranecell membrane

Why is this important?Why is this important?

Ion ChannelIon Channel

Some pores are always open, others Some pores are always open, others have a gate which can be open or have a gate which can be open or closed.closed.

They can open or close in response to They can open or close in response to different kinds of stimuli.different kinds of stimuli.

ex. Electrical charge or binding ex. Electrical charge or binding sites.sites.

Facilitated DiffusionFacilitated Diffusion

Facilitated Diffusion – a type of Facilitated Diffusion – a type of passive transport that moves passive transport that moves substances down their concentration substances down their concentration gradient without using the cells gradient without using the cells energy. energy.

Transport proteins transport Transport proteins transport substances across the cell substances across the cell membrane. These are called carrier membrane. These are called carrier proteins.proteins.

Facilitated DiffusionFacilitated Diffusion

ChallengeChallenge

Why do drawers get sticky when Why do drawers get sticky when there has been a lot of rain or high there has been a lot of rain or high humidity.humidity.

During the winter , salt is sprinkled During the winter , salt is sprinkled over icy roads. Plants growing along over icy roads. Plants growing along side the road are often seriously side the road are often seriously damaged or dead. Why does this damaged or dead. Why does this happen?happen?