CELL TRANSPORTCELL TRANSPORT

Define these terms:1. Solute * 2. Solvent *3. Semipermeable Membrane*4. Passive Transport* 5.Active Transport*6. Diffusion*7. Osmosis*8. Concentration Gradient9. Facilitated Diffusion10. Hypertonic 11. Hypotonic12. Isotonic

How do molecules get into the cell?

•By crossing the Cell Membrane!

What is a key property of the Cell Membrane?

• Selective Permeability!!Selective Permeability!!• This propertyproperty of biological biological

membranesmembranes allows some substances to cross more easily than others.

How much energy will it cost the cell to MOVE molecules in

or out? • It depends on HOW it enters the cell!

• Which do you think does NOT “cost” the cell energy- Passive Transport or ActiveTransport?

PASSIVE TRANSPORT

First type Passive Transport-First type Passive Transport- DiffusionDiffusion

• What is it?

– Random movement of molecules down a concentrationconcentration gradientgradient from an area of highhigh concentrationconcentration to an area of lowlow concentrationconcentration.

• NONO energyenergy is expended.• ALWAYS high concentration to low concentration!

Diffusion

Watch this animation!

• http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_diffusion_works.html

• http://www.indiana.edu/~phys215/lecture/lecnotes/diff.html

2nd type Passive Transport-2nd type Passive Transport- OsmosisOsmosis

• The diffusion of waterwater across selectively permeable membranesselectively permeable membranes.

• WaterWater moves from a highhigh water water concentrationconcentration to lowlow water water concentrationconcentration.

• NO energy expended by cell

3nd type passive transport Facilitated Diffusion

Type which uses transport proteinstransport proteins to to move molecules across the membrane move molecules across the membrane WITHOUTWITHOUT any energy expended by cell! any energy expended by cell!

Always high concentration to Low Always high concentration to Low concentrationconcentration

!!

Question:Question:What’s in a Solution?What’s in a Solution?

Answer:Answer:

• solutesolute + solventsolvent solutionsolution

• NaClNaCl + HH2200 saltwatersaltwater

HypertonicHypertonic• A solutionsolution with greater solutegreater solute c concentrationoncentration

(less water) compared to inside the cellinside the cell.

3% NaCl97% H2O

Red Blood Cell

5% NaCl95% H2O

solutionsolution

HypotonicHypotonic• A solutionsolution with lower solute concentrationlower solute concentration

((more watermore water) ) compared to inside the cellinside the cell.

3% Na97% H2O

Red Blood Cell

1% Na99% H2O

solutionsolution

IsotonicIsotonic• A solutionsolution with an equal solute concentrationequal solute concentration

compared to inside the cellinside the cell.• This solution is said to be in Dynamic Dynamic

equilibriumequilibrium.

3% Na97% H2O

Red Blood Cell

3% Na97% H2O

solutionsolution

Movement of HMovement of H22O = OSMOSIS!O = OSMOSIS!

• Water will “ALWAYS”“ALWAYS” diffuse down a concentration gradient from a HYPOTONICHYPOTONIC solutionsolution (more water, less solute)(more water, less solute) to a HYPERTONICHYPERTONIC solution solution (less water, more (less water, more solute). solute).

ALWAYS REMEMBER- water moves fromALWAYS REMEMBER- water moves from• HYPOTONICHYPOTONIC HYPERTONICHYPERTONIC

Animal CellsAnimal Cells

• Animal cellsAnimal cells placed into a hypotonic hypotonic solutionsolution will EXPLODE.EXPLODE.

Hypotonic

RedRedBloodBloodCellCell

Animal CellsAnimal Cells

• Animal cellsAnimal cells placed into a hypertonic hypertonic solutionsolution will SHRIVEL.SHRIVEL.

Hypertonic

RedRedBloodBloodCellCell

Plant CellsPlant Cells• In a hypotonic environment, the vacuole is full

of water (cell gains water), and the cell membrane is pushed against the cell wall. The cell wall helps the plant cell retain its shape under the tension.

WaterWater

CellWall Water

CentralVacuole

Plant CellsPlant Cells• In a hypertonic environmenthypertonic environment (loss of water)(loss of water), ,

the plasma membraneplasma membrane pulls away from the cell wallcell wall (vacuole empty)(vacuole empty).

Water Water

CellWall Water

plasma membraneplasma membrane

Active TransportActive Transport

• The movement of moleculesmovement of molecules (small or large) across the plasma plasma membranemembrane using energy (ATP)energy (ATP).

Examples of Active Transport:

Active transport using a carrier Active transport using a carrier molecule in the membranemolecule in the membrane - many times, this involves moving - many times, this involves moving molecules from a molecules from a lowlow to to highhigh concentration (OPPOSITE the concentration (OPPOSITE the direction during diffusion!).direction during diffusion!).

- - Requires ATP (ENERGY!!) to move Requires ATP (ENERGY!!) to move it across!it across!

Protein pumps

• Some membrane proteins use energy to pump substances in and out of the cell.

• Sodium potassium pump animation.

• How are How are largelarge molecules molecules transported into and out of transported into and out of the cell?the cell?

• Endocytosis and Exocytosis Endocytosis and Exocytosis ((BOTHBOTH are active transport!) are active transport!)

Endocytosis• ENTRY into cell

• Portion of the membrane surrounds or engulfs a macromolecule (large molecule) outside cell. The membrane pinches off to form a vesicle in the cytoplasm

• Requires Energy!!

Endocytosis, cont.Different names for type macromolecules

endocytosed:

– Pinocytosis: endocytosis of liquids– Phagocytosis: endocytosis of

particles – http://www.stolaf.edu/people/giannini/flashanimat/cellstructures/

phagocitosis.swf

Endocytosis, cont.

• Amoeba feeding

Exocytosis:•EXPORT of materials OUT of

the cell (wastes, cell products)

- Also a type of Active Transport (energy required!!)

MODELLING A CELL MEMBRANE

Plastic baggies are a lot like cell membranes; they are semipermeable.

• Do baggies allow any of the following - water, starch, or iodine - to move through them?

• Materials:1.baggies2.Starch suspension

in H2O3.Iodine solution4.Beakers

Wrap up of Transport across a Semipermeable membrane!

• BEFORE you get your beaker, write down what you EXPECTED to happen? (Who moved across the plastic membrane?)

How did your experiment work? • Did the liquid in the beaker or the

baggie change color? What does it indicate?

• Decide WHICH molecules were transported- water, iodine, or starch?

• Did your experiment test all 3 components?

Cont….• Things to think about:

– Size of atoms/ molecules– Set-up of experiment- could you

detect movement of ALL molecules?– Validity/ reliability

• How is the baggy LIKE a cell membrane?

• How is it NOT LIKE a cell membrane?

Wrap-up!• Standard 10.1: FUNDAMENTAL life

processes depend on the physical and chemical activities of the cell.– D30. Explain the role of the cell

membrane in supporting cell functions.• What ARE the roles of the cell

membrane?

Wrap-up!

How is the cell membrane structured to ensure efficiency and survival?

DO Now!

• Sheet 3.5–Complete and we will discuss it

Concentration ProblemsIn each problem below, the membrane is

permeable to water only!1. Which way will water move – into or out of the body cell? (draw an arrow!)

2. The solution is ________.

3. Which way will water move – into or out of the sphere? (draw an arrow!)

4. Is the solution in the beaker hypotonic, isotonic, or hypertonic compared to the cell? (Circle one!)

5. Which way will water move – into or out of the sphere? (draw an

arrow!)

6. What will happen to the shape / size of the sphere? What is the solution outside the cell?

Cell

0.45 M

solute

7. Which way will water move – into or out of the body cell? (draw

an arrow!)

8. What is the cell’s solute concentration after dynamic equilibrium is reached?

0.35 M solute

9. Which way will water move – into or out of the body cell? (draw an

arrow!)

cell

10. What is the cell’s water concentration after dynamic equilibrium is reached?