Warm-Up #4 11/1/12Warm-Up #4 11/1/121) What are the 2 other names for the cell 1) What are the 2 other names for the cell

membrane?membrane?

2) If a molecule is too big to go through 2) If a molecule is too big to go through the membrane alone, what must it the membrane alone, what must it use?use?

3) Label A-D on the Picture below.3) Label A-D on the Picture below.

4) What is the quiz tomorrow on?4) What is the quiz tomorrow on?

Passive Transport: Diffusion Passive Transport: Diffusion and Osmosisand Osmosis

Unit 4Unit 4Chapter 5Chapter 5

What are we doing?What are we doing?• Essential Essential

Question:Question:• How do How do

organisms organisms maintain maintain homeostasis?homeostasis?

• Objectives:Objectives:• Explain how an Explain how an

equilibrium is equilibrium is established as a established as a result of diffusion.result of diffusion.

• Distinguish Distinguish between diffusion between diffusion and osmosis.and osmosis.

Passive TransportPassive Transport• Movement of Movement of

substances across substances across the cell the cell membrane membrane without the use of without the use of ATP (Energy)ATP (Energy)

Concentration GradientConcentration Gradient• The difference in the concentration The difference in the concentration

of molecules across a space.of molecules across a space.• Diffusion always occurs DOWN the Diffusion always occurs DOWN the

concentration gradient.concentration gradient.

EquilibriumEquilibrium• Equi--equalEqui--equal• When the concentration of When the concentration of

molecules of a substance is the molecules of a substance is the SAMESAME throughout a space throughout a space

DiffusionDiffusion• Simplest type of passive Simplest type of passive

transporttransport• NO energy neededNO energy needed• Always goes from an Always goes from an

area of higher area of higher concentration to lower concentration to lower concentrationconcentration

• Example: Example: • Gas exchange in lungsGas exchange in lungs• PhotosynthesisPhotosynthesis

Rate of DiffusionRate of Diffusion• Rate depends on three things:Rate depends on three things:• 1. Temperature1. Temperature

• Higher the temperature faster the Higher the temperature faster the diffusiondiffusion

• 2. Size2. Size• Smaller the molecule, faster the diffusionSmaller the molecule, faster the diffusion

• 3. Type of Molecules3. Type of Molecules• Bigger molecules will not pass through Bigger molecules will not pass through

without energy inputwithout energy input

OsmosisOsmosis• Diffusion of water Diffusion of water

across a semi- across a semi- permeable permeable membranemembrane

• Move from high to Move from high to low concentrationlow concentration

When does this happen?When does this happen?• Water moves from areas of LOW Water moves from areas of LOW

solute concentration to areas of solute concentration to areas of HIGH solute concentrationsHIGH solute concentrations

• Will do this until they are evenly Will do this until they are evenly distributeddistributed

Hypertonic SolutionHypertonic Solution• The concentration of solute The concentration of solute

molecules outside the cell is higher molecules outside the cell is higher than the concentration of solutes than the concentration of solutes inside the cell.inside the cell.

• Water Diffuses OUT of the Cell until Water Diffuses OUT of the Cell until equilibrium occursequilibrium occurs

Animal vs. Plants in Animal vs. Plants in Hypertonic SolutionsHypertonic Solutions

• Animal Cell:Animal Cell:• Cell shrivels and Cell shrivels and

shrinksshrinks

• Plant Cell:Plant Cell:• Cell membrane Cell membrane

pulls away from pulls away from the cell wallthe cell wall

PlasmolysisPlasmolysis• Plants lose water through osmosis.Plants lose water through osmosis.• It occurs when the cell membrane It occurs when the cell membrane

peels away from the cell wall.peels away from the cell wall.• The plant shrivels and dies.The plant shrivels and dies.

HypotonicHypotonic• The concentration of solute The concentration of solute

molecules outside the cell is lower molecules outside the cell is lower than the concentration of solutes than the concentration of solutes inside the cellinside the cell

• Water diffuses INTO the cell until Water diffuses INTO the cell until equilibrium is reachedequilibrium is reached

Animal vs. Plant Cells--Animal vs. Plant Cells--HypotonicHypotonic

• Animal CellAnimal Cell• Cell will swells and Cell will swells and

burstsbursts

• Plant CellPlant Cell• DOES NOT burst DOES NOT burst

because of cell because of cell wallwall

• Called Turgor Called Turgor PressurePressure

Isotonic SolutionIsotonic Solution• The concentration of solutes The concentration of solutes

outside and inside the cell are outside and inside the cell are equal.equal.

• Water diffuses into and out of the Water diffuses into and out of the cell at equal ratecell at equal rate

Help…I Need Somebody…Help…I Need Somebody…

• Facilitated DiffusionFacilitated Diffusion• Use of carrier proteins to help substances Use of carrier proteins to help substances

move in or out of the cellmove in or out of the cell• No Energy NeededNo Energy Needed

What do the Proteins Do?What do the Proteins Do?• Carry molecules Carry molecules

across the across the membrane—membrane—carrier proteinscarrier proteins

• Change shape to Change shape to help the molecule help the molecule pass throughpass through

SolutionSolution Animal CellAnimal Cell Plant CellPlant CellIsotonic:Isotonic:The The concentration of concentration of solutes is the solutes is the same inside and same inside and outside of the outside of the cellcellHypertonic:Hypertonic:Solution has a Solution has a higher solute higher solute concentration concentration than the cellthan the cellHypotonic:Hypotonic:Solution has a Solution has a lower solute lower solute concentration concentration than the cellthan the cell

WARM-UP #4 WARM-UP #4 11/3/1111/3/11

1)1) What does passive transport not What does passive transport not require?require?

2)2) What are 2 types of passive What are 2 types of passive transport?transport?

3)3) The movement of molecules The movement of molecules across a membrane is called……?across a membrane is called……?

4)4) Osmosis is the movement of____.Osmosis is the movement of____.