Osmosis, Diffusion Presentation

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CELL TRANSPORT

Constant Motion of MoleculesKinetic Theory of MatterMolecules move randomly and bump intoeach other and other barriers

Solvent and Solute Solution – homogenousliquid throughout whichtwo or more substancesare dispersed Solvent – the substancein which a solute isdissolved in order tocreate a solution Solute – the substancedissolved in the solventin order to create asolution

Concentration GradientConcentration Gradient – difference in concentration ofmolecules across a distance

Equilibrium Equilibrium – the concentration of solute isuniform throughout the solution In the absence of other influences, moleculeswill naturally reach equilibrium

DiffusionMolecules in solution tend to slowly spreadapart over time. This is diffusion.T1T2T3

Diffusion Movement of molecules from an area of highconcentration to an area of lower concentration.Applies to any kind of solution.Factors that affect the rate of diffusion: size ofmolecules, size of pores in membrane, temperature,pressure, and concentration.

Diffusion will continue until equilibrium is reached. Thismeans there will be an equal distribution of moleculesthroughout the space.This is why food coloring moves throughout a beaker of water;why odors smell strong at first and then disappear over time.

Which molecules will diffuse ineach of the figures below?125364

ANSWERS1234No Movement56No Movement

PASSIVE TRANSPORT Passive transport occurs without expenditure of energy.Molecules move using their own kinetic energy.Diffusion is an example of passive transport.Passive transport allows cells to get oxygen and othersmall molecules. It also allows the cell to get rid of waste such as carbondioxide.

Facilitated Diffusion Polar molecules will not readily diffuse through thenon-polar interior of the lipid bilayer. Facilitated Diffusion uses protein channels that acceptparticular molecules and pass them through based onconcentration gradients. Because there is no energy expended, facilitateddiffusion is a form of passive transport. Example: movement of glucose

Osmosis Osmosis is the movement of WATER across asemi-permeable membrane At first the concentration of solute is very high onthe left. But over time, the water moves across the semipermeable membrane and dilutes the particles.

Hypotonic – The solution on one side of a membrane where the soluteconcentration is less than on the other side. Hypotonic Solutions contain alow concentration of solute relative to another solution.Hypertonic – The solution on one side of a membrane where the soluteconcentration is greater than on the other side. Hypertonic Solutionscontain a high concentration of solute relative to another solution.

Over time molecules will move across themembrane until the concentration of solutes isequal on both sides (equilibrium.) This type ofsolution is called isotonic.

WaterWaterSoluteSolute

Osmosis in Cells Diffusion of water across a selectively permeable membrane (a barrierthat allows some substances to pass but not others). The cell membraneis such a barrier.Small molecules pass through – ex: oxygen, carbon dioxide (lipid soluble)Large molecules can’t pass through – ex: proteins and complexcarbohydratesWater is a polar molecule so uses facilitated diffusion through specializedproteins called water channels.

Cytoplasm is a solution of water and solids(solutes dissolved in the water).Water moves into and out of cells because of the differentconcentrations of the solutes.Different kinds of cells react differently depending on the solutionthey are in.Below are examples of red blood cells in different types of solutionsand shows what happened to the red blood cells.

The Real World Most organisms function in isotonic environments whereosmosis does not present a problem. Some organisms live in hypotonic or hypertonic environmentsand osmosis becomes a challenge to maintaininghomeostasis.Halophilic micro-algae inhypertonic environmentMaintain homeostasis byaccumulatingcompounds in theircytoplasm.

Contractile Vacuole Other organisms life in hypotonic environments, which alsopresent a problem for maintaining homeostasis. Paramecium have a contractile vacuole that collects excesswater and then contracts to remove it from the cell.

Osmosis in Plant Cells Most plants live in hypotonicenvironments. Water enters cell and collectsin central vacuole. Rigid cell wall prevents lysisand stops osmosis, creates apressure called turgorpressure. In hypertonic environment, the reverse happens and thecell shrinks away from the cell wall – a condition calledplasmolysis. Turgor is lost and the cell loses structure.

PLANT CELLSHypotonicSolutionTurgor Pressure builds in thecell and causes osmosis to stopbecause of the rigid cell wall.HypertonicSolutionPlants will wilt when cellslose water through osmosis.

ELODEA CELLSAs viewed under the microscope

Turgor maintainedPlasmolysis - wilting

ACTIVE TRANSPORTActive Transport uses energy to move molecules and substances across membranes.

Active Transport requires energy.In cells, energy means ATP.carrierphosphates

In Active Transport carrier proteins useATP (energy) to move substances againstthe concentration gradient.

Examples of Active TransportCell Membrane Pumps(such as the Sodium-Potassium pump)Endocytosis & Exocytosis (Bulk Transport)(such as pinocytosis and phagocytosis)Contractile Vacuoles(such as the organelles in some protozoans)

Cell Membrane PumpsCarrier proteins not only assist in passive transport, asin facilitated diffusion, but they can also be used foractive transport as cell membrane “pumps.”Moves substances (hydrogen ions) against the concentration gradient.

A carrier protein binds to aspecific molecule on one sideof the membrane, changesshape – shielding themolecule from thephospholipids – transportsthe molecule to the otherside, and then releases it.

Bulk Transportphagocytosis: large particles ingestedpinocytosis: liquid ingestedreceptor-mediated: recognition with coated pits

PASSIVE TRANSPORT Passive transport occurs without expenditure of energy . Molecules move using their own kinetic energy. Diffusion is an example of passive transport. Passive transport allows cells to get oxygen and other small molecules. It also al

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