Cell Boundaries and Movement

Cell Barriers• Cell membranes

– Structure: contain a flexible lipid bilayer with imbedded protein molecules and carbohydrate molecules

– Function: Substances move across the cell membrane through

A.) lipid bilayerB.) protein channelsC.) assistance of protein moleculesD.) Processes of endocytosis and exocytosis

Cell Barriers• Cell Walls

– Structure: made mostly of tough carbohydrate fiber called cellulose

– Function: Cell walls support and protect cells; cell walls are porous and allows substances to move through easily

Types of Movement Through Cells

A.) DiffusionB.) OsmosisC.) Facilitated DiffusionD.) Active Transport

Diffusion• Substances move across the

cell membrane from areas of high solute concentration to areas of low solute concentration until equilibrium is reached

• No energy required• Substances continue to

move back and forth across the membrane once equilibrium is reached

Osmosis• The diffusion of water across a cell membrane• Types of osmotic solutions

– Hypotonic– Isotonic– Hypertonic

ConcentrationConcentration of a solution is the mass of solute in a

given volume of solution, or mass/volume

A Solute is a substance that is dissolved in a solvent to make a solution

Which way will the water move?

Hypotonic Solution

• the solution has a lower solute concentration than the cell so water moves into the cell causing plant cells to swell and animal cells to swell and burst

Lower solute concentration

Lower solute concentration outside cell

Animal Cell

Lower solute concentration outside cell

Plant Cell

Isotonic Solution

• The concentration of solutes is equal inside and outside the cell so water moves across the membrane in both directions maintaining cell size

Animal Cell

Plant Cell

Equal solute concentration inside and outside cell

Equal solute concentration inside and outside cell

Hypertonic Solution

• The solution has a higher solute concentration than the cell so water moves out of the cell and into the solution causing the cell to plasmolyze

Animal Cell

Plant Cell

higher solute concentration outside cell

higher solute concentration outside cell

CELL MEMBRANE

Lipid layer 1

Lipid layer 2

Proteins

Facilitated DiffusionA) Substance specific

protein channels allow movement of molecules such as glucose to move across the membrane in either direction

B) Substances still move high concentration to low concentration and no energy is required

Active Transport• Characteristics:

– Movement of substances is against the concentration gradient

– Energy is required !

• Types of Active Transport– Molecular transport– Endocytosis– Exocytosis

REMEMBER:

Requires ATP

Energy!

Active Transport – Molecular Transport

• Molecular transport: Protein molecules act like energy requiring pumps to move molecules and ions across membranes

I NEED THOSE GREEN THINGS!

Active Transport – EndocytosisEndocytosis – Materials are taken into the cell by

means of forming in the cell membrane. The pocket becomes a vacuole inside the cell.

ENDOCYTOSIS

ENDOCYTOSIS

• Cool video showing Endocytosishttp://www.youtube.com/watch?v=lgHJUkGPBqs

• Paramecium EATS 2 amoebashttp://www.youtube.com/watch?v=pvOz4V699gk&feature=fvwrel

Exocytosis

Exocytosis – EXPEL WASTES FROM CELL Wastes moved out of the cell when a vacuole fuses

with the cell membrane

Active Transport – Exocytosis

VIDEO of EXOCYTOSIS

• http://www.youtube.com/watch?v=U9pvm_4-bHg