THE CELL MEMBRANE All cells contain cell membranes

THE CELL MEMBRANE �All cells contain cell membranes �Cell membranes support and protect the cell, and regulate what enters and exits the cell to maintain homeostasis. �Cell Membranes are made up of a lipid bilayer—a double layer of lipids with proteins embedded and exist in a water environment

CELL MEMBRANE

CELL MEMBRANE �The cell membrane is selectively permeable —some substances can pass through it but others cannot.

PASSIVE TRNSPORT �Passive transport—the movement of materials across the cell membrane without the use of energy

TYPES OF PASSIVE TRANSPORT � Diffusion—the movement of molecules from an area of high concentration to an area of low concentration. � Substances will move toward the area where it is less concentrated until it is evenly distributed. � Equilibrium—When the concentration of a substance on both sides of the cell membrane is the same.

DIFFUSION

CONCENTRATION GRADIENT �The concentration gradient is the direction particles move in order to reach equilibrium. The concentration gradient is always from high concentrations to low concentrations in passive transport.

FACILITATED DIFFUSION � Facilitated diffusion—When channel proteins embedded in the cell membrane facilitate, or help, the diffusion of specific materials across the cell membrane. � There are hundreds of different channel proteins that allow specific substances across the cell membrane. Ex: Channel proteins help glucose molecules move into a cell

OSMOSIS �Osmosis—The diffusion of water through a selectively permeable membrane. �Water will move across the membrane until equilibrium is reached.

THE EFFECTS OF OSMOSIS ON CELLS

TYPES OF ACTIVE TRANSPORT � Active transport requires energy. It involves moving molecules against the concentration gradient. � Movement of molecules from low to high concentrations requires energy. � 2 types of active transport: � Molecular (small molecules) � Bulk (larger molecules or clumps of molecules)

WHICH IS ACTIVE AND WHICH IS PASSIVE TRANSPORT AND HOW DO YOU KNOW? Diamonds – active – going from low to high concentration Circles – passive - going from high to low concentration

REVIEW OF PASSIVE AND ACTIVE TRANSPORT 1. If molecule D moves from side A to side B is that active or passive transport? Active – going from low to high concentration 2. Which way would molecule C move assuming this was a water molecule diffusing across a selectively permeable membrane in order to reach equilibrium? to the right 3. What do we specifically call the diffusion of water?