Starter

• Why can you smell the manure when it is being spread in fields miles away?

• Why can you smell perfume when a girl sprays it on herself from all the way across the room?

• What will happen when I drop food coloring into the flask at the front of the room?

Starter

• Based off of your lab, why must cells be small?• How might temperature and size of molecules

effect diffusion across the membrane?• Essay: Using all of the animal cell organelles,

explain how they all work together to run as an efficient system.

Starter

• Finish Lab• How does this lab illustrate the definition of

diffusion?

The Cell Membrane

Movement Across

Structure

• Phospholipid Bilayer– Phosphate Heads• Hydrophilic

– Fatty Acid Tails• Hydrophobic

– 2 layers, tail to tail– Embedded Proteins• Gets “things” in and out of the cell

What has to get in and out?

• Molecules, ions and….WATER!– Water is always moving across the membrane– Movement of these substances helps cells to

maintain homeostasis• Stable internal environment regardless of external

conditions– Cell needs to be happy!

Passive vs. Active Transport

• Passive– No energy needed– High Concentration

low concentration• Diffusion• Facilitated Diffusion• Osmosis

• Active– Energy is needed– Low concentration

High concentration• Transport protein pumps• Exocytosis• Endocytosis

Diffusion

• Movement of molecules from an area of high concentration to low concentration– Always think “high to low”• Air freshener• Cow Manure

• Depends on temperature and size of molecule diffusing– Fast – hot/small– Slow – cold/large

Osmosis

• The diffusion of water across a semi-permeable membrane– Semi-permeable – only certain molecules can pass

• Water moves across a membrane from high water concentration to an area of low water concentration– Goes to where there is more “stuff”

Osmosis

• *****Water always moves to where there is more “stuff” (more concentrate)

Concentration?

• The amount of a particular substance in a certain amount of another substance– Huh?• Orange Juice

– Concentrate vs. Jug– Which has more “stuff”

Concentration

• Solution– Uniform mixture of two or more substances• Salt water

• Solute– Substance that is dissolved• Salt

• Solvent– Substance doing the dissolving• Water

Solutions

• Hypertonic– More solute outside the cell• Water rushes out• Cell shrinks

• Hypotonic– More solute inside the cell• Water rushes in• Cell swells

Solutions

• Isotonic– Same concentration of solutes/water inside and

outside of the cell• Water still moves in and out

– It is at the same rate!

• Cell stays the same

Facilitated Diffusion

• Carrier proteins– Large and not liked by the fatty acid tails– Recognize specific molecules to bring into the cell– Must be the proper molecule to enter• Sugars