AgendaAgenda

1. FA #12

2. Methods of Transportation Notes p.133-134

3. Osmosis Lab (Handout)

4. Organelle Study Guide

5. Grab books, read section, and complete objectives.

Methods of Movement in the Cell

Diffusion, Osmosis, & Active Transport

p. 133-134 in binder

Cell MembraneCell Membrane

• Selectively Permeable “Gate Keeper”– Some substances can pass through the

cell membrane while others cannot.– Good things go into the cell, bad things

stay out– Ex. Water, oxygen, carbon dioxide are

permeable but large molecules & salt stay out

Outsideof cell

Insideof cell(cytoplasm)

Cellmembrane

Proteins

Proteinchannel Lipid bilayer

Carbohydratechains

Cell MembraneCell Membrane

3 Methods of Moving Substances In & Out of the Cell

3 Methods of Moving Substances In & Out of the Cell

• Diffusion

• Osmosis

• Active Transport

DiffusionDiffusion

• Movement of molecules from an area in which they are highly concentrated to an area in which they are less concentrated.

• Ex. In one celled pond organisms, the oxygen moves from the water into the cell.

OsmosisOsmosis

• Diffusion/movement of water across a selectively permeable membrane.

• Water moves from a high concentration of water (less salt or sugar dissolved in it) to a low concentration of water (more salt or sugar dissolved in it). 

OsmosisOsmosis

Osmosis in Red Blood CellsOsmosis in Red Blood Cells

• Figure A: Red blood cells are in solution in which concentration of water is the same as it is inside the cells. (Normal)

• Figure B: RBCs are in water with high salt concentration.• Figure C: RBCs are in water with very low salt

concentration, less than the cell salt concentration.

Passive TransportPassive Transport

• Riding a bike downhill doesn’t take any energy to go fast, right?

• But pedaling your bike uphill does.• Diffusion & Osmosis are like riding your bike

downhill.– Movement from high to low concentration doesn’t

require energy.

• Passive Transport– Movement of materials through a cell membrane

without using energy—highlow. (Diffusion & Osmosis)

Active TransportActive Transport

• What if a cell needs to take in a substance that is in higher concentration inside the cell than outside?

• The cell would have to move the molecules in the opposite direction that they naturally do. (Pedaling uphill)

• Active Transport– Movement of materials through a cell

membrane that requires energy. Low High

Methods of Active TransportMethods of Active Transport

• Transport Proteins– Proteins “pick up”

molecules outside the cell and carry them in.

– Ex. Calcium (Ca), Potassium (K), and Sodium (Na)

Molecule tobe carried

Moleculebeing carried

Energy

Methods of Active Transport (cont.d)

Methods of Active Transport (cont.d)

• Transport by Engulfing– Cell surrounds, or engulfs, a particle.

So…Why Is Movement of Materials Important?

So…Why Is Movement of Materials Important?

• All living things have certain requirements they must satisfy in order to remain alive. – Exchanging gases (usually CO2 and O2),– Taking in water, minerals, and food– Eliminating wastes

• These tasks ultimately occur at the cellular level, and require that molecules move through the membrane that surrounds the cell.

Why Are Cells So Small?Why Are Cells So Small?

• As a cell’s size increases, more of its cytoplasm is located farther from the cell membrane.

• Once a molecule enters the cell it is carried to its destination by streams of moving cytoplasm.

• In a very large cell, the streams of cytoplasm must travel farther to bring materials to all parts of the cell.

• Much more difficult for molecule to reach center of cell.

• Wastes need to be removed.

SummarySummary

• Cell membrane is– A complex structure that is responsible

for…• Separating the contents of the cell from its

surroundings• Controlling the movement of materials into and

out of the cell

• Cell movement occurs by…– Diffusion, Osmosis, & Active Transport

Osmosis LabOsmosis Lab

• Read through handout EXTREMELY WELL• Complete Prelab on p.185.• Perform the Lab

– Completed at your lab groups in 4’s.– Supplies can be found on the back lab table.– Cover cups with aluminum foil or saran wrap.

• Make sure that someone from your group will come in on FRIDAY to get the completed results.

Organelle Study GuideOrganelle Study Guide

1. See example.

2. Fold outward flaps in.

3. Cut along dotted lines

4. Color organelle

5. Write function on the backside of the flap.

6. Write name underneath the flap.