Unit B 9 & 10: Cell Biology Unit B 9 & 10: Cell Biology (Transport Across Cell (Transport Across Cell

Membrane)Membrane)Authored by Michelle ChomaAuthored by Michelle Choma©©

Students who have fully met the prescribed learning outcomes Students who have fully met the prescribed learning outcomes (PLO’s) are able to:(PLO’s) are able to:

B9. Analyze the structure and B9. Analyze the structure and function of the cell membrane.function of the cell membrane.

• apply knowledge of organic molecules – apply knowledge of organic molecules – including phospholipids, proteins, including phospholipids, proteins, glycoproteins, glycolipids, carbohydrates, glycoproteins, glycolipids, carbohydrates, and cholesterol – to explain the structure and cholesterol – to explain the structure and function of the fluid-mosaic membrane and function of the fluid-mosaic membrane model.model.

Analyze the structure and Analyze the structure and function of the cell membrane.function of the cell membrane.

(continued)(continued)• identify the hydrophobic and hydrophilic regions of identify the hydrophobic and hydrophilic regions of

the phospholipid bilayer.the phospholipid bilayer.• explain why the cell membrane is described as explain why the cell membrane is described as

“selectively permeable”.“selectively permeable”.• describe passive transport processes including describe passive transport processes including

diffusion, osmosis, and facilitated transport. diffusion, osmosis, and facilitated transport. • explain factors that affect the rate of diffusion across explain factors that affect the rate of diffusion across

a cell membrane (e.g., temperature, size of molecule, a cell membrane (e.g., temperature, size of molecule, charge of molecule, concentration gradient, pressure charge of molecule, concentration gradient, pressure gradient).gradient).

• predict the effects of hypertonic, isotonic, and predict the effects of hypertonic, isotonic, and hypertonic environments on osmosis in animal cells.hypertonic environments on osmosis in animal cells.

And a little bit more….And a little bit more…. describe active transport processes including describe active transport processes including

active transport, endocytosis (Phagocytosis and active transport, endocytosis (Phagocytosis and pinocytosis), and exocytosis.pinocytosis), and exocytosis.

compare specific transport processes – including compare specific transport processes – including diffusion, osmosis, facilitated transport, active diffusion, osmosis, facilitated transport, active transport, endocytosis and exocytosis – in terms transport, endocytosis and exocytosis – in terms of:of:

concentration gradientconcentration gradient use of channel or carrier proteinuse of channel or carrier protein use of energyuse of energy types/sizes of molecules transportedtypes/sizes of molecules transported

devise an experiment using the scientific devise an experiment using the scientific method (e.g. to investigate the tonicity of cells). method (e.g. to investigate the tonicity of cells). Spud Lab!Spud Lab!

B10. Explain why cells divide B10. Explain why cells divide when they reach a particular when they reach a particular surface area-to-volume ratio.surface area-to-volume ratio.

differentiate between cells that have differentiate between cells that have a high or low surface area-to-volume a high or low surface area-to-volume ratio.ratio.

demonstrate an understanding of the demonstrate an understanding of the significance of surface-area-to-significance of surface-area-to-volume ratio in cell size.volume ratio in cell size. Short one eh!?Short one eh!?

Web Sites for Cell Web Sites for Cell TransportTransport

http://http://www.coolschool.ca/content/available_courses.phpwww.coolschool.ca/content/available_courses.php (Unit 04) Scroll to (Unit 04) Scroll to Lesson 01 – Lesson 08Lesson 01 – Lesson 08 (‘U04L01 – L08’) (‘U04L01 – L08’)

http://highered.mcgraw-hill.com/sites/http://highered.mcgraw-hill.com/sites/0072421975/student_view0/chapter4/ (Mader’s 0072421975/student_view0/chapter4/ (Mader’s Student Edition Website Support for Chapter 4; Student Edition Website Support for Chapter 4; Animations, quizzes, flashcards, Thinking Animations, quizzes, flashcards, Thinking Scientifically etc.)Scientifically etc.)

http://www.mhhe.com/biosci/genbio/espv2/data/http://www.mhhe.com/biosci/genbio/espv2/data/cells/003/index.html (Essential Study Partner: CM cells/003/index.html (Essential Study Partner: CM & Cell Transport)& Cell Transport)

http://www.ibiblio.org/virtualcell/textbook/http://www.ibiblio.org/virtualcell/textbook/chapter3/cms1.htm (Cell membrane structure chapter3/cms1.htm (Cell membrane structure text & animation)text & animation)

More websitesMore websites http://sps.k12.ar.us/massengale/biology%20classhttp://sps.k12.ar.us/massengale/biology%20class

%20notes2.htm%20notes2.htm (A terrific site with animations, self-quiz, notes (A terrific site with animations, self-quiz, notes etc. Click on the various etc. Click on the various notesnotes for for Effect of Effect of Solutions on Cells, Web Tutorials on Passive & Solutions on Cells, Web Tutorials on Passive & Active Transport, Scientific Method, and Active Transport, Scientific Method, and Designing an ExperimentDesigning an Experiment))

http://www.wiley.com/legacy/college/boyer/http://www.wiley.com/legacy/college/boyer/0470003790/animations/membrane_transport/0470003790/animations/membrane_transport/membrane_transport.htm (Animation of Cell membrane_transport.htm (Animation of Cell Transport)Transport)

http://curriculum.calstatela.edu/courses/builders/http://curriculum.calstatela.edu/courses/builders/lessons/less/les4/cellsize.html (Limits to Cell Size)lessons/less/les4/cellsize.html (Limits to Cell Size)

And a few moreAnd a few more http://science.nhmccd.edu/biol/bio1int.htm http://science.nhmccd.edu/biol/bio1int.htm http://sps.k12.ar.us/massengale/http://sps.k12.ar.us/massengale/

pwpt_biology.htm pwpt_biology.htm (Terrific power points on (Terrific power points on Scientific MethodScientific Method and and Identifying Controls & VariablesIdentifying Controls & Variables))

www.emc.maricopa.edu/.../www.emc.maricopa.edu/.../BioBooktransp.htmlBioBooktransp.html

http://fig.cox.miami.edu/~cmallery/150/http://fig.cox.miami.edu/~cmallery/150/memb/membranememb/membranes.htms.htm

http://www.citruscollege.edu/apps/pub.asp?http://www.citruscollege.edu/apps/pub.asp?Q=808&T=Tutoring%20Services&B=4 Q=808&T=Tutoring%20Services&B=4

B9 - Cell Membrane B9 - Cell Membrane StructureStructure

IntroductionIntroduction The ‘fluid-mosaic model’ is a model The ‘fluid-mosaic model’ is a model

that describes the structures of the that describes the structures of the CM, i.e. a fluid lipid layer in a mosaic CM, i.e. a fluid lipid layer in a mosaic made up of many different types of made up of many different types of molecules. Cell membranes include a molecules. Cell membranes include a flexible bilayer of flexible bilayer of phospholipidsphospholipids interspersed with large interspersed with large protein protein moleculesmolecules that aid in membrane that aid in membrane transport and transport and cholesterolcholesterol for rigidity.for rigidity.

Structure of the Plasma MembraneStructure of the Plasma Membrane

Structure of the Plasma MembraneStructure of the Plasma Membrane

PhospholipidPhospholipid bilayerbilayer

PhospholipidPhospholipid–– Hydrophilic headHydrophilic head–– Hydrophobic tailsHydrophobic tails

CholesterolCholesterol

ProteinsProteins–– TransmembraneTransmembrane//

Intrinsic/IntegralIntrinsic/Integral–– Peripheral/ExtrinsicPeripheral/Extrinsic

CytoskeletalCytoskeletal filamentsfilaments

Carbohydrate chainCarbohydrate chain

GlycoproteinsGlycoproteins

GlycolipidsGlycolipids

1.) Phospholipid bilayer1.) Phospholipid bilayer

Make up the basic structural unit of Make up the basic structural unit of the cell membrane.the cell membrane.

Contains a Contains a charged polar headcharged polar head ((hydrophilichydrophilic/‘H/‘H22O- loving’) and O- loving’) and non-non-polarpolar, , fat-soluble tailsfat-soluble tails ((hydrophobichydrophobic/‘H/‘H22O-fearing’).O-fearing’).

Fluid-like consistency.Fluid-like consistency.

Phospholipid bilayerPhospholipid bilayer

FunctionsFunctions Allows Allows lipid-solublelipid-soluble molecules such as molecules such as

alcohol, Oalcohol, O22, CO, CO22 and lipid soluble and lipid soluble molecules, i.e. lipids, steroids, (and molecules, i.e. lipids, steroids, (and vitamins A & E) to pass through the vitamins A & E) to pass through the phospholipid bilayer.phospholipid bilayer.

Provides flexibility and fluidity thus Provides flexibility and fluidity thus allowing allowing vesiclesvesicles to form. to form.

Prevents Prevents non-lipid solublenon-lipid soluble moleculesmolecules, , e.g. water, ions, amino acids and e.g. water, ions, amino acids and monosaccharides to pass through.monosaccharides to pass through.

Note: Lack of permeability to ions sets up membrane potential (See C11: Nerve transmission).

2.) Proteins2.) Proteins

Form a “mosaic” pattern/scattered Form a “mosaic” pattern/scattered throughout the phospholipid bilayer.throughout the phospholipid bilayer.

Largely determine the cell membrane’s Largely determine the cell membrane’s functions.functions.

Embedded in cell membrane and on the Embedded in cell membrane and on the surfaces; 3surfaces; 3oo structures act as carriers, structures act as carriers, pumps, channels, receptors and cell pumps, channels, receptors and cell recognition proteins.recognition proteins.

ProteinsProteins

FunctionsFunctions Some act as Some act as carrierscarriers bringing bringing amino amino

acidsacids, , ionsions, and , and glucoseglucose in/out, e.g. in/out, e.g. Na+/K+ pump in nerve transmission; Na+/K+ pump in nerve transmission; protein carriers bringing in glucose protein carriers bringing in glucose for RBC’s; or concentrating for RBC’s; or concentrating molecules/ions inside or outside of molecules/ions inside or outside of cell, e.g. nerve cells actively cell, e.g. nerve cells actively pumping Na+ & K+ or thyroid cells pumping Na+ & K+ or thyroid cells concentrating iodine. concentrating iodine.

Some have Some have channels/gates/poreschannels/gates/pores to allow to allow passage of Hpassage of H22O, dissolved ions, and small O, dissolved ions, and small

molecules.molecules.

Some are Some are receptorsreceptors that a specific molecule can that a specific molecule can bind to, e.g. bind to, e.g. hormoneshormones such as insulin, thyroxin, such as insulin, thyroxin,

aldosterone, estrogen, testosterone etc. or aldosterone, estrogen, testosterone etc. or neurotransmittersneurotransmitters such as acetylcholine (ACh), such as acetylcholine (ACh),

norepinephrine (NE).norepinephrine (NE).

http://www.mhhe.com/biosci/genbio/espv2/data/cells/003/index.html

3.) Glycoproteins and 3.) Glycoproteins and GlycolipidsGlycolipids

Attached to outside of cell membraneAttached to outside of cell membrane **NOTNOT found on intra-cellular membranes found on intra-cellular membranes

(e.g. mitochondria, ER, Golgi, etc.)(e.g. mitochondria, ER, Golgi, etc.) Made up of Made up of carbohydrate-chainscarbohydrate-chains

attached to a phospholipid head or a attached to a phospholipid head or a protein.protein.

FunctionFunction: - Serves as : - Serves as recognition sitesrecognition sites allowing organisms to recognize foreign allowing organisms to recognize foreign cells/molecules.cells/molecules.

4.) Cholesterol4.) Cholesterol

Abundant lipids found wedged Abundant lipids found wedged between the phospholipids. between the phospholipids.

FunctionFunction: - Stiffen CM and provides : - Stiffen CM and provides more flexibility.more flexibility.

Note: Note: CytoskeletonCytoskeleton (Recall Unit B1) is an internal (Recall Unit B1) is an internal framework of framework of protein fibresprotein fibres that gives the that gives the

cytoplasm strength and flexibility and provides cytoplasm strength and flexibility and provides movement of organelles. Some protein filaments movement of organelles. Some protein filaments

attaches to the integral proteins of the CM.attaches to the integral proteins of the CM.

Attachment of the CytoskeletonAttachment of the Cytoskeleton

Summary of Cell Membrane Summary of Cell Membrane Structures and FunctionsStructures and Functions

Molecules Functions Unit molecules

Proteins Allows/selects certain Allows/selects certain molecules in/out of molecules in/out of cell through cell through channels/gates/pochannels/gates/poresres. E.g. H. E.g. H22O, OO, O22, , COCO22, ions. , ions.

CarriesCarries molecules molecules selectively in/out of selectively in/out of cell by carriers. E.g. cell by carriers. E.g. NaNa++, K, K++, C, C66HH1212OO66, ,

áá’s, HCOáá’s, HCO33--, Ca, Ca2+2+..

Amino acids

Protein Function ContProtein Function Cont CatalyzesCatalyzes reactions on cell surface by enzymatic proteins. reactions on cell surface by enzymatic proteins.

E.g. Enzymes for ATP metabolism or breakdown of ATP for E.g. Enzymes for ATP metabolism or breakdown of ATP for Na+ transport.Na+ transport.

Provides Provides receptor sitesreceptor sites by receptor proteins. E.g. by receptor proteins. E.g. Hormones having the same shape as receptor proteins to Hormones having the same shape as receptor proteins to bind to it.bind to it.

Phospholipids (a) Allows for diffusion of lipid soluble molecules. E.g. O2, CO2, and alcohol.

(b) Allows for flexibility & fluidity of cell membrane.E.g. Vesicle formation.(c) Excludes H2O and ions.

(d) Acts as a boundary keeping organelles within the cell.

2 fatty acids (saturated/

unsaturated) & 1 glycerol, N and phosphate group

Glycolipids and Glycoproteins

(a) Used in cell identification.(b) Glycoproteins can form a carbohydrate coat that envelops the cell membrane (glycocalyx).

Chains of carbohydrates

attached to lipid or protein

Cholesterol Stiffen CM and provide flexibility

Backbone of 4 fused C-H rings

B9 – Selectively Permeable B9 – Selectively Permeable Cell MembraneCell Membrane

Cell membrane is described as Cell membrane is described as selectively permeableselectively permeable because it because it allows only certain molecules or ions allows only certain molecules or ions to pass through it, i.e. it limits what to pass through it, i.e. it limits what can move across.can move across.

*Functions of Cell Membrane*Functions of Cell Membrane

RegulatesRegulates the exit/entrance of molecules/ions the exit/entrance of molecules/ions via via pinocytosis/phagocytosis/endocytosis/exocytosis.pinocytosis/phagocytosis/endocytosis/exocytosis.

RegulatesRegulates the exit/entrance of molecules/ions the exit/entrance of molecules/ions via diffusion/facilitated transport/active via diffusion/facilitated transport/active transport/osmosis.transport/osmosis.

Used in Used in cell identificationcell identification via glycoproteins and via glycoproteins and glycolipids.glycolipids.

CatalyzesCatalyzes reactions on the cell surface via reactions on the cell surface via enzymatic proteins.enzymatic proteins.

Provides Provides receptor sitesreceptor sites via receptor proteins for via receptor proteins for certain molecules.certain molecules.

Acts as a Acts as a cell boundarycell boundary keeping the organelles keeping the organelles within the cell.within the cell.

B9 – Entrance/Exit of B9 – Entrance/Exit of MoleculesMolecules

Introduction: Terms to know Introduction: Terms to know

SolventSolvent - the dissolving agent, usually H - the dissolving agent, usually H22O. O. SoluteSolute - molecules, ions dissolved in the solvent. - molecules, ions dissolved in the solvent. Concentration Concentration -- # of molecules in a given unit of # of molecules in a given unit of

volume.volume. GradientGradient- - the physical difference between two the physical difference between two

regions which cause molecules to move from one regions which cause molecules to move from one region to the other and tends to equalize the region to the other and tends to equalize the difference.difference.

Concentration gradientConcentration gradient - the difference in solute - the difference in solute concentration between two regions resulting in concentration between two regions resulting in molecular movement.molecular movement.

Osmotic pressureOsmotic pressure - pressure generated by H - pressure generated by H22O O moving by osmosis into or out of a cell. moving by osmosis into or out of a cell.

Note---ie. Pay Attention!!Note---ie. Pay Attention!!

Osmotic pressure always moves Osmotic pressure always moves water toward the hypertonic side water toward the hypertonic side (the side containing the least (the side containing the least amount of water) of a amount of water) of a membrane.membrane.

Some more terms….Some more terms….

Hydrostatic pressureHydrostatic pressure – pressure exerted by – pressure exerted by the weight of Hthe weight of H22O/fluid pushing against a O/fluid pushing against a surface, e.g. capillary.surface, e.g. capillary.

TonicityTonicity - total solute concentration of the - total solute concentration of the solution outside the cell; causes the cell to solution outside the cell; causes the cell to gain or lose Hgain or lose H22O.O.

TurgorTurgor (‘to swell’)- the rigid state of a cell (‘to swell’)- the rigid state of a cell (especially plants) caused by osmotic (especially plants) caused by osmotic pressure of the cytoplasm against the cell pressure of the cytoplasm against the cell wall or membrane.wall or membrane.

There are There are twotwo main categories main categories of transport across selectively of transport across selectively

permeable membranes:permeable membranes:

1.) 1.) Passive transportPassive transport Movement of molecules from [high] to Movement of molecules from [high] to

[low] (along a concentration gradient).[low] (along a concentration gradient). Does not require energy; some use Does not require energy; some use

specific CM proteins; does not use specific CM proteins; does not use vesicles; involves movement of small vesicles; involves movement of small molecules, water (osmosis), ions, molecules, water (osmosis), ions, CC66HH1212OO66, amino acids, fatty acids. , amino acids, fatty acids.

Second type of transportSecond type of transport

2.) 2.) Active transportActive transport Movement of molecules from [low] to Movement of molecules from [low] to

[high] and energy (ATP) is required [high] and energy (ATP) is required (against a concentration gradient).(against a concentration gradient).

Requires energy; uses carrier or Requires energy; uses carrier or receptor proteins; can use vesicle receptor proteins; can use vesicle formation; involves movement of formation; involves movement of small & large molecules, ions, cells, small & large molecules, ions, cells, microorganisms. microorganisms.

Passive TransportPassive Transport

Materials/molecules can move by 3 Materials/molecules can move by 3 processes:processes: (a) (a) DiffusionDiffusion.. (b) (b) Facilitated transport/diffusionFacilitated transport/diffusion.. (c) (c) OsmosisOsmosis..

Diffusion

Osmosis

examples of lab equipment which examples of lab equipment which demonstrate diffusion and osmosis, i.e. the demonstrate diffusion and osmosis, i.e. the

osmometerosmometer and and U-tubeU-tube apparatusapparatus..

DiffusionDiffusion Net movement of molecules/ions from an Net movement of molecules/ions from an

area of area of [[highhigh] to [] to [lowlow].]. Requires Requires no energyno energy and molecules must be and molecules must be

lipid solublelipid soluble.. Large molecules, proteins, polysaccharides, Large molecules, proteins, polysaccharides,

nucleic acids, and charged ions cannot nucleic acids, and charged ions cannot diffuse across.diffuse across.

Small, uncharged molecules (COSmall, uncharged molecules (CO22, O2) can , O2) can enter easily, e.g. Oenter easily, e.g. O22 and CO and CO2 2 diffuse across diffuse across membranes of alveoli (See C10); Hmembranes of alveoli (See C10); H22O as well O as well via channel proteins/ “via channel proteins/ “aquaporinsaquaporins” (osmosis).” (osmosis).

Diffusion ContinuedDiffusion Continued

CC66HH1212OO66, amino acids, fatty acids and ions , amino acids, fatty acids and ions diffuse via CM proteins, e.g. diffuse via CM proteins, e.g. neurotransmitters (NT’s) diffusing across neurotransmitters (NT’s) diffusing across the synaptic cleft during nerve the synaptic cleft during nerve impulses/synapse OR impulses/synapse OR

CaCa2+2+ diffusing across the presynaptic diffusing across the presynaptic membrane during nerve impulses/synapse membrane during nerve impulses/synapse (See C11); monomers diffusing into (See C11); monomers diffusing into epithelial cells of villi (See C1). epithelial cells of villi (See C1).

AnimationsAnimations

http://www.coolschool.ca/lor/BI12/unit4/http://www.coolschool.ca/lor/BI12/unit4/U04L03/diffusion.swf U04L03/diffusion.swf

http://highered.mcgraw-hill.com/sites/http://highered.mcgraw-hill.com/sites/0072421975/student_view0/chapter4/0072421975/student_view0/chapter4/animations__english_.html (Diffusion)animations__english_.html (Diffusion)

http://www.wiley.com/legacy/college/http://www.wiley.com/legacy/college/boyer/0470003790/animations/boyer/0470003790/animations/membrane_transport/membrane_transport/membrane_transport.htmmembrane_transport.htm

Facilitated Transport/DiffusionFacilitated Transport/Diffusion

Net movement of molecules from an area Net movement of molecules from an area of of [[highhigh] to [] to [lowlow]] using using carrier proteinscarrier proteins to get across the cell membrane.to get across the cell membrane.

Requires Requires no ATPno ATP.. Involves protein carriers that are highly Involves protein carriers that are highly

specific to the substance and transports it specific to the substance and transports it at a at a faster ratefaster rate..

E.g. CE.g. C66HH1212OO66, sucrose, amino acids and ions , sucrose, amino acids and ions insoluble in the lipid bilayer can be insoluble in the lipid bilayer can be transported along a concentration gradient transported along a concentration gradient across the cell membrane using a carrier across the cell membrane using a carrier protein to enter quickly.protein to enter quickly.

OsmosisOsmosis (See diagrams and worksheet)(See diagrams and worksheet)

Net diffusion of Net diffusion of HH22OO only from only from [high] [high] toto [low][low] across a cell membrane via CM across a cell membrane via CM proteins (channel proteins/“proteins (channel proteins/“aquaporinsaquaporins”).”).

OROR Net diffusion of Net diffusion of HH22OO from an area of from an area of

[lower solute][lower solute] toto [higher solute][higher solute] across a cell membrane via CM proteins across a cell membrane via CM proteins (channel proteins/“(channel proteins/“aquaporinsaquaporins”).”).

AnimationsAnimations

http://www.phschool.com/science/http://www.phschool.com/science/biology_place/labbench/lab1/osmosis.html biology_place/labbench/lab1/osmosis.html

http://www.coolschool.ca/lor/BI12/unit4/http://www.coolschool.ca/lor/BI12/unit4/U04L03/osmosis.swf U04L03/osmosis.swf

http://www.coolschool.ca/lor/BI12/unit4/http://www.coolschool.ca/lor/BI12/unit4/U04L06/rbc.html (interactive RBC)U04L06/rbc.html (interactive RBC)

http://www.wiley.com/legacy/college/http://www.wiley.com/legacy/college/boyer/0470003790/animations/boyer/0470003790/animations/membrane_transport/membrane_transport/membrane_transport.htm membrane_transport.htm

OsmosisOsmosis

There are There are threethree conditions of conditions of tonicity/osmosis:tonicity/osmosis:

i) i) IsotonicIsotonic (“equal solute and H (“equal solute and H220”)0”) ii) ii) Hypotonic Hypotonic (“less solute, more H(“less solute, more H220”)0”) iii) iii) HypertonicHypertonic (“more solute, less H (“more solute, less H220”)0”)

If the concentration of solute (salt) is equal on both sides, water will move back in forth but it won't have any result on the overall amount of water on either side.

"ISO" means the same.

IsotonicIsotonic

HypotonicHypotonic"HYPO" means less. There are less solute (salt) molecules outside the cell, which causes water to move into the cell by osmosis (high to low).The cell will gain water & grow larger. In plant cells, the central vacuole will fill and the plant becomes stiff and rigid, i.e. turgor. The cell wall keeps the plant from bursting.In human animal cells, the cell is in danger of lysis or bursting.

HypertonicHypertonic

HypertonicHypertonic ""HYPERHYPER" means more. There are " means more. There are more solute more solute

(salt) molecules outside the cell, which causes (salt) molecules outside the cell, which causes the water to leave the cell by osmosis (high to the water to leave the cell by osmosis (high to low).low).

In plant cells, the central vacuole loses water; the In plant cells, the central vacuole loses water; the cells shrink, i.e. plasmolysis causing wilting.cells shrink, i.e. plasmolysis causing wilting.

In animal cells, the cells also shrink. In both In animal cells, the cells also shrink. In both cases, the cell may die.cases, the cell may die.

It is dangerous to drink sea water. People It is dangerous to drink sea water. People marooned at sea will speed up dehydration (and marooned at sea will speed up dehydration (and death) by drinking sea water. This is also why death) by drinking sea water. This is also why "salting fields" was a common tactic during war, it "salting fields" was a common tactic during war, it would kill the crops, thus causing food shortages. would kill the crops, thus causing food shortages.

Isotonic:Isotonic:

iso iso – equal– equal tonicitytonicity – solute – solute

The solution has the The solution has the same/equalsame/equal [solute] as the [solute] inside the [solute] as the [solute] inside the cell.cell.

This results in the cell This results in the cell notnot gaining or gaining or losing Hlosing H22O.O.

IsotonicIsotonic

95% H205% salt

95% H2O5% salt

Isotonic Solution

95% H2O5% saltHH22O moves in/out of red O moves in/out of red

blood cells (RBC) at equal blood cells (RBC) at equal rates and the shape rates and the shape remains as biconcave.remains as biconcave.

Hypotonic:Hypotonic:

hypohypo – less – less tonicitytonicity – solute – solute

The solution has a The solution has a lowerlower [solute] [solute] than the [solute] inside the cell.than the [solute] inside the cell.

This results in the movement of This results in the movement of water (osmosis) water (osmosis) INTOINTO the cell causing the cell causing it to swell and burst causing it to swell and burst causing lysislysis..

HypotonicHypotonic

HH22O moves into O moves into the RBC by the RBC by osmosis, causing osmosis, causing it to swell and it to swell and lysislysis to occur. to occur.

95% H205% salt

98% H2O2% salt

Hypotonic Solution

Example of a RBC placed in a hypotonic solution.

RBC shape in the beginning of the experiment?After 2 minutes?

Hypertonic:Hypertonic:

hyperhyper – more – more tonicitytonicity – solute – solute The solution has a The solution has a highehigher r [solute] [solute]

than the [solute] inside the cell.than the [solute] inside the cell. This results in the movement of This results in the movement of

water (osmosis) water (osmosis) OUTOUT of the cell of the cell causing it to causing it to shrivelshrivel or in the case of or in the case of RBC’s, RBC’s, crenationcrenation occurs; in plant occurs; in plant cells, cells, plasmolysisplasmolysis occurs. occurs.

HypertonicHypertonic

H2O moves OUT of the RBC’s by osmosis causing it to shrivel and undergo crenation.

HypertonicHypertonic

In In plant cellsplant cells, H, H22O O moves moves OUTOUT of the of the cytoplasm by cytoplasm by osmosis causing osmosis causing the cell membrane the cell membrane to pull away from to pull away from the cell wall. This the cell wall. This is termed is termed plasmolysisplasmolysis. .