chapter 7 cell structure & function section 7-3 movement through the membranes

Chapter 7Chapter 7Cell Structure & FunctionCell Structure & Function

Section 7-3Section 7-3Movement Through The MembranesMovement Through The Membranes

ObjectivesObjectives

What are the main functions of the What are the main functions of the cell membrane and the cell wall?cell membrane and the cell wall?

What happens during diffusion?What happens during diffusion?

What is osmosis?What is osmosis?

The Cell MembraneThe Cell Membrane

Key Concept:Key Concept:

The cell membrane The cell membrane regulates what enters regulates what enters and leaves the cell and and leaves the cell and also provides protection also provides protection and supportand support

The Cell MembraneThe Cell Membrane

The cell takes in nutrients and The cell takes in nutrients and expels wastes plus cell products expels wastes plus cell products through the cell membranethrough the cell membrane

The Basic Structure Of Nearly All The Basic Structure Of Nearly All Cell Membranes Is The Cell Membranes Is The LIPID LIPID BILAYERBILAYER

LIPID BILAYERSLIPID BILAYERS

Form Automatically When Form Automatically When Certain Lipids Are Dissolved In Certain Lipids Are Dissolved In WaterWater

Tough Flexible StructureTough Flexible Structure Strong Barrier Between Cell Strong Barrier Between Cell

Contents And Its SurroundingsContents And Its Surroundings

LIPID BILAYERSLIPID BILAYERS

Fluid Mosaic ModelFluid Mosaic Model

In Addition To The Bilayer, The In Addition To The Bilayer, The Cell Membrane Contains:Cell Membrane Contains:

Proteins That FormProteins That Form Channels & PumpsChannels & Pumps

Proteins with Carbohydrates That FormProteins with Carbohydrates That Form Antigenic SitesAntigenic Sites Communication SitesCommunication Sites

DiffusionDiffusion

All Living Cells Contain And Are All Living Cells Contain And Are Surrounded By Liquid.Surrounded By Liquid.

THE CELL MEMBRANE THE CELL MEMBRANE REGULATES THE MOVEMENT OF REGULATES THE MOVEMENT OF MOLECULES FROM ONE SIDE OF MOLECULES FROM ONE SIDE OF THE MEMBRANE TO THE OTHERTHE MEMBRANE TO THE OTHER

CytoplasmCytoplasm

Is A Solution Of Many Is A Solution Of Many Different Substances In Different Substances In

WaterWater

SolutionSolution

A liquid mixture of 2 or more A liquid mixture of 2 or more substances evenly mixed.substances evenly mixed.

SolventSolvent The liquid in which the substances The liquid in which the substances

are mixedare mixed SoluteSolute

Substances dissolved in the SolventSubstances dissolved in the Solvent

Concentration Of SolutionConcentration Of Solution

Mass of the solute in a given Mass of the solute in a given volume of solvent.volume of solvent.

Mass/VolumeMass/Volume e.g.e.g.

12 g. of NaCl dissolved in 3L H12 g. of NaCl dissolved in 3L H22OO==

12g./3 l. or 4.0 g/L12g./3 l. or 4.0 g/L

In A SolutionIn A Solution

Molecules Are Moving Constantly Molecules Are Moving Constantly They Collide and Bounce off each otherThey Collide and Bounce off each other

This causes them to spread out This causes them to spread out randomlyrandomly

Resulting In:Resulting In:

Movement from an area of higher Movement from an area of higher concentration to and area of lower concentration to and area of lower concentrationconcentration

DIFFUSIONDIFFUSION

Molecules move away from an Molecules move away from an area of Higher Concentration to area of Higher Concentration to area’s of Lower Concentrationarea’s of Lower Concentration

EquilibriumEquilibrium Concentration of a solute is the Concentration of a solute is the

same throughout the solutionsame throughout the solution

DiffusionDiffusion

DIFFUSIONDIFFUSION

Key ConceptKey Concept::

Diffusion Causes Many Diffusion Causes Many Substances To Move Across A Substances To Move Across A Cell Membrane But:Cell Membrane But:

Does Does NOTNOT Require The CellRequire The Cell

To Use EnergyTo Use Energy

Diffusion across a Diffusion across a membranemembrane

Diffusion & CellsDiffusion & Cells

Substances that can diffuse Substances that can diffuse across cell membranes will do across cell membranes will do so until equilibrium is reachedso until equilibrium is reached

Diffusion Diffusion continuescontinues afterafter equilibriumequilibrium but the rates in but the rates in and out are equaland out are equal

OSMOSISOSMOSIS

OsmosisOsmosis

Permeable MembranePermeable Membrane Substance Can Easily CrossSubstance Can Easily Cross

Impermeable MembraneImpermeable Membrane Substance Can NOT CrossSubstance Can NOT Cross

Selectively Permeable MembraneSelectively Permeable Membrane Some Substances Can Cross, Some Substances Can Cross,

Others Can NotOthers Can Not

OSMOSISOSMOSIS

Key ConceptKey Concept::

The Diffusion Of The Diffusion Of WaterWater ThroughThrough A A Selectively Selectively Permeable MembranePermeable Membrane

The TonicsThe Tonics

HypotonicHypotonic Less concentrated solutionLess concentrated solution

IsotonicIsotonic Equally concentrated solutionEqually concentrated solution

HypertonicHypertonic More Highly concentrated solutionMore Highly concentrated solution

The TonicsThe Tonics

Osmotic PressureOsmotic Pressure

Pressure exerted on the Pressure exerted on the hypertonic side of a hypertonic side of a selectively permeable selectively permeable membranemembrane

May cause cells to shrink or May cause cells to shrink or burstburst

Osmotic PressureOsmotic PressureCell Walls

Contractile Vacuoles

Facilitated DiffusionFacilitated Diffusion

Molecules that can easily Molecules that can easily diffuse across the cell diffuse across the cell membrane:membrane: AlcoholAlcohol WaterWater Small LipidsSmall Lipids


Other molecules can not pass Other molecules can not pass through the cell membrane through the cell membrane but still get into the cell.but still get into the cell.

HOW?HOW?


Thru Protein Channels in the Cell Thru Protein Channels in the Cell Membrane that allow a Membrane that allow a substance to cross.substance to cross. Allows Diffusion In Both DirectionsAllows Diffusion In Both Directions Each Channel Substance SpecificEach Channel Substance Specific DOES DOES NOTNOT REQUIRE ENERGY REQUIRE ENERGY


Protein Channel Is Substrate Specific

Substrate Can Move Either Direction Depending On Concentration. Always from area of Higher Concentration to area of Lower

Concentration!

Active TransportActive Transport

Moves Material Across A Cell Moves Material Across A Cell MembraneMembrane

AgainstAgainst A Concentration A Concentration GradientGradient

(from area of Lower concentration into an (from area of Lower concentration into an area of Higher concentration)area of Higher concentration)


Requires EnergyRequires Energy

Energy Molecule

Active TransportActive Transport EndocytosisEndocytosis

Used to bring in large molecules, Used to bring in large molecules, food, and whole cellsfood, and whole cells

ExocytosisExocytosis Membrane surrounded material from Membrane surrounded material from

inside the cell fuses with the cell inside the cell fuses with the cell membrane, releasing the contents.membrane, releasing the contents.

chapter 7 cell structure & function section 7-3 movement through the membranes

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