Cell Boundaries (Chapter 7.3)

Please set up your notebook for Cornell Notes

Cell membrane (plasma membrane) Regulates the movement of materials into

and out of the cell (selectively permeable) Made of a phospholipid bilayer

◦ Outer and inner layers are hydrophilic (water-loving)

◦ Middle is hydrophobic (water-fearing)◦ Has different molecules embedded

Proteins, carbohydrates◦ Called a fluid mosaic

Diffusion Movement of particles from where there is

more (high concentration) to where there is less (low concentration)◦ Moving down the concentration gradient

Once both sides of the membrane are at equal concentration, this is equilibrium◦ Net movement = 0, but particles are still moving

Does not require energy Movement of particles is random

Osmosis The diffusion of water through a membrane Depends on the concentration of the solutions

◦ Solution a mixture of two or more substances (sugar water) Solvent the material doing the dissolving (water) Solute the material being dissolved (sugar)

◦ Solutions and membranes Isotonic the solutions on either side of the membrane have the

same concentration; net movement = 0 If the solution has lower concentration of solutes than the cell, then

the solution is hypotonic to the cell Water will move into the cell

If the solution has a higher concentration of solutes than the cell then the solution is hypertonic to the cell Water will move out of the cell

◦ Water moves from areas of low concentration to areas of high concentration

Facilitated diffusion Used for particles that are too big to get

through the cell membrane◦ Moves down the concentration gradient (requires no

energy) Channel proteins move particles through the

membrane

Active transport Movement of material from where there is less to

where there is more (up concentration gradient) Requires energy (ATP) Endocytosis bringing materials into the cell by

creating pockets in the cell membrane◦ Phagocytosis extensions of cytoplasm surround particle

and package it in a vacuole◦ Pinocytosis bringing liquid into the cell using pockets of cell

membrane Exocytosis using vacuoles to excel materials from

the cell