diffusion of chemical substances importantdiffusion of chemical substances importantdiffusion of chemical substances importantdiffusion of chemical substances importantin keeping living organisms alive andin keeping living organisms alive andin keeping living organisms alive andin keeping living organisms alive andgrowinggrowinggrowinggrowing

movement of carbon dioxideduring photosynthesistranspirationmovement of oxygen andcarbon dioxide in animals

DiffusionDiffusionDiffusionDiffusion

process

molecules are dispersed in arandom directionspread from an area of higherconcentration to an area of lowerconcentrationdispersion continues untilmolecules are evenlydistributedhomogeneous state/equilibrium

the net movement of molecules movingthe net movement of molecules movingthe net movement of molecules movingthe net movement of molecules movingfrom a region of higher concentration to afrom a region of higher concentration to afrom a region of higher concentration to afrom a region of higher concentration to aregion of lower concentration to reachregion of lower concentration to reachregion of lower concentration to reachregion of lower concentration to reachequillibrium (the movement is down aequillibrium (the movement is down aequillibrium (the movement is down aequillibrium (the movement is down aconcentration gradient)concentration gradient)concentration gradient)concentration gradient)substances are movedwithout the use of energy

Concentration GradientConcentration GradientConcentration GradientConcentration Gradient

the difference in concentration between tworegions is known as the concentrationgradientthe steeper the concentration gradient,the faster the movement of themolecules

Molecules/ ParticlesMolecules/ ParticlesMolecules/ ParticlesMolecules/ Particles

matter is made up of small, discretemolecules/ particles in constant randommotion

OsmosisOsmosisOsmosisOsmosis

water potential is a measure of thetendency of water to move from one placeto another

a dilute solution contains more watermolecules than a concentrated solution,hence it has a higher water potential

the passage of water from a region of higherthe passage of water from a region of higherthe passage of water from a region of higherthe passage of water from a region of higherwater potential through a particularwater potential through a particularwater potential through a particularwater potential through a particularpermeable membrane to a region of lowerpermeable membrane to a region of lowerpermeable membrane to a region of lowerpermeable membrane to a region of lowerwater potentialwater potentialwater potentialwater potential

Hypotonic SolutionHypotonic SolutionHypotonic SolutionHypotonic Solution

medium surrounding cell hashigher water potential thancellmore water will enter the cellthan will leave

net result: water will enter --> cellbecomes turgid (plant)/ bursts(animal)

Isotonic SolutionIsotonic SolutionIsotonic SolutionIsotonic Solution

medium is exactly the samewater potential as the cellamount of water going in isthe same as the water goingoutnet result: no movement -->cell stays the same size

Hypertonic SolutionHypertonic SolutionHypertonic SolutionHypertonic Solution

medium has lower waterpotential than cell

more water will leave the cellthan will enter

net result: water will leave -->cell becomes plasmolysed(plant)/ crenated (animal)PlasmolysisPlasmolysisPlasmolysisPlasmolysis

occurs when water is drawn out ofthe cell and into the extracellularfluid

the [plant] cell membraneshrinks away from its cellwall

MembranesMembranesMembranesMembranes

PermeablePermeablePermeablePermeableallows all molecules to passthrough it

Partially PermeablePartially PermeablePartially PermeablePartially Permeable

only allows certainmolecules to pass throughitplasma membrane(surrounding the cell)small molecules like oxygen,water, carbon dioxide,ammonia, glucose, aminoacids, etc. can pass throughlarger molecules like sucrose,starch, protein, etc. cannot passthrough

separates the internal cellenvironment from the externalenvironmentcontrols passage ofmolecules acrossmembranes

Movement of Substances inMovement of Substances inMovement of Substances inMovement of Substances inLiving ThingsLiving ThingsLiving ThingsLiving Things