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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