Movement Through A Membrane (Cell Transport)

A few terms…

• Concentration – ratio or proportion of solute to solvent

• Diffusion – Movement of materials across the cell membrane

• Homeostasis – balance of materials necessary for life, equilibrium

Add these!

• Solvent – Liquid water• Solute – solid (salt or sugar)

Cell Membrane

• Fluid Mosaic Model– Phospholipid

Bilayer– Transport Proteins

• Selectively Permeable

What Needs to go Across

• Water

• Food (Glucose)

• Raw materials (Proteins)

• Waste

• Finished proteins

Uses No Energy

• Osmosis• Passive Transport• Facilitated Diffusion

• High conc low

Osmosis

• Diffusion of water across the membrane

Diffusion/Passive Transport

• Movement of other materials across the cell membrane

• Facilitated Diffusion –large molecules get help across the cell membrane– Transport Proteins are “doors”

Passive Transport

• Equilibrium – Balance of materials on both sides of

the membrane

Describing Solutions by their Effect on Cells

Uses Energy

• Active Transport– Low conc high

• Endocytosis/Exocytosis

Endocytosis

• Materials enter the cell– Cell membrane “pinches in” and forms vesicle

inside the cell

Exocytosis

• Materials exit the cell– Membrane wrapped particles merge with the

cell membrane and are pushed into the environment

Which one is it?

Homeostasis

• Dynamic Equilibrium– Constant change in

order to stay in balance