Head
Hydrophilic end of phospholipid
Tails
Hydrophobic end of phospholipid
Passive transport
Diffusion of molecules across a cell membrane
Diffusion
The tendency of molecules to spread out evenly in available space
Osmosis
Diffusion of water across a cell membrane
Facilitated Diffusion
Diffusion of molecules down the concentration gradient with the help of a transport protein
Concentration gradient
Movement of molecules from high concentration to low concentration
Isotonic
Solute concentration outside the cell is the same as solute concentration inside of the cell
Hypertonic
Solute concentration outside the cell is greater that solute concentration inside of the cell; Cell loses water
Hypotonic
Solute concentration outside the cell is less than solute concentration inside of the cell; Cell gains water
Plasmolysis
In a hypertonic solution around a plant cell the cell membrane pulls away from the cell wall
Active transport
Movement of molecules across the cell membrane that requires energy; Molecules go against the concentration gradient from low to high
Sodium-Potassium pump
Example of active transport to transmit nerve signals in the body
Exocytosis
Occurs when a cell exports bulky materials out of the cell
Endocytosis
Occurs when a cell takes in large molecules by forming vesicles
Phagocytosis
Cell membrane changes shape and surrounds the particle and engulfs it.
Pinocytosis
The membrane bends inward allowing the particle to 'dissolve' through the membrane