How do things get in and out?

The Cell Membrane

Plasma Membrane(aka Cell Membrane)

• Phosopholipid Bilayer

• Called the Fluid Mosaic Model

• Selectively Permeable

Selectively Permeable

If a membrane is selectively permeable only

certain things can pass through

The Cell Membrane is Selective:

• Things that pass through lipid layer: – Non-Polar Molecules (Alcohols, Steroids)

– Small Molecules (Water)

• Things that require protein channels: – Polar Molecules (Ions)

– Large Molecules

Active (requires ATP)

Passive (no ATP)

Types of Transport

Transport mediaMembrane Transport from Pearson

Transport across membranes from Bozeman

Northland college: complete cell membrane movements

Passive TransportMovement of

materials that DOES NOT require energy

(ATP)

Osmosis

Passive

Passive Transport

Diffusion

Facilitated Diffusion

What is happening here???

DIFFUSIONThe passive movement

of material from an area of high concentration to

an area of low concentration

ConcentrationThe number of a

substance in a specific area

High Concentration

Low Concentration

Factors Affecting Diffusion• Concentration—diffusion always goes from

high concentration to low concetration

• Temperature—the higher the temperature, the faster diffusion occurs

• Molecular size—the bigger the molecule, the longer diffusion takes

• Mixing/shaking/stirring

OSMOSISThe diffusion of water through a selectively

permeable membrane

Osmosis—another look…

Osmotic Pressure

The force (pressure) of water on a cell membrane

Types of Solutions

Isotonic SolutionEqual concentratino on both sides of a embraneRESULT: No net movement of water in or out of the cell

Hypotonic Solution

When the side of a membrane has a lower solute concentration, or higher water concentration

Hypotonic SolutionRESULT: Water moves from the solution into the cell causing it to swell or break (lysis)

Hypertonic SolutionRESULT: The water moves out of the cell

into the solution, causing the cell to

shrink

Why doesn’t the plant cell undergo lysis?

WHITEBOARDINGIn your groups draw what the cells would look like in

each case.Effect of Osmosis on Cells

Animal Cell

Solution Before After

Isotonic

Hypotonic

Hypertonic

Explain what is

happening in this

cartoon…

Facilitated Diffusion

Diffusion that is helped by proteins in

the membrane

Facillitated Diffusion

Diffusion vs. Facillitated Diffusion

MembraneMovements

Active

Cellular Transport

Ion Pumps

Endocytosis Exocytosis

Phagocytosis

Osmosis

Passive

Diffusion

Facilitated Diffusion

Pinocytosis Receptor-mediatedEndocytosis

Active TransportMovement of materials

from low concentration to high concentration using a

protein carrier that requires energy

(costs ATP)

What was ATP again???

Sodium-Potassium Pump

Active Transport

Endocytosis and Exocytosis

EndocytosisProcess of bringing

particles into a cell using extensions of the cellular

membrane

ExocytosisProcess of moving particles

out of a cell using extensions of the cellular

membrane (how wastes are excreted

from cells)

PinocytosisThe process of

membrane folding that enables cells to bring “water” into the cell

(a.k.a. cellular drinking)

PhagocytosisThe process of

membrane folding that enables cells to bring “food” into the cell

(a.k.a. cellular eating)