Phospholipid bilayer: • a double layer of lipids makes up most of the cell membrane. • Proteins: many proteins are embedded in the phospholipid bilayer • Some act as channels to transport materials through the membrane • Some are connected to carbohydrate chains on the exterior of the cell • Carbohydrates: • Short chains of carbohydrates are connected to proteins or lipids on the exterior surface of the cell • They act as markers to identify the cell
Selectively Permeable • Cell membranes act as barriers, controlling which materials enter and leave the cell • Materials can enter or leave the cell based on their size and the amount of substance present(concentration)
Cell Transport PassiveTransport:small molecules can cross over the cell membrane without using extra energy Diffusion:small particles flow down a con- centration gradient from an area of high [concentration] to an area of [low] Osmosis:the diffusion of water molecules over the cell membrane Facilitated Diffusion: particles still travel from [high] to [low], but they pass through channels in the membrane Example: ions • Raw Egg Osmosis Demonstration
Types of Solutions and Movement of Water Hypertonic Solutions • Hypertonic solutions have a HIGHER concentration of solutes than what is inside the cell • This causes water to move OUT of the cell. • Hypertonic environments shrink animal cells.
Hypotonic Solution • Hypotonic solutions have a LOWER concentration of solutes than what is inside the cell • This causes water to move INTO the cell. • Hypotonic environments swell animal cells.
Isotonic Solutions • Isotonic solutions have THE SAME concen- trationof solutes as what is inside the cell • While water will move in and out, there is no NET movement of molecules. • Isotonic environments cause no net change.
Active Transport Active Transport requires additional energy, because substances are being transported AGAINST the concen- tration gradient(from [low] [high]) Endocytosis: endo: within cyt: cell -osis: process of the process of taking materials into a cell by forming vesicles around the substance pinocytosis:pin: to drink cells taking in substances dissolved in water phagocytosis:phag: to eat cells taking in large particles Exocytosis: exo- from outside the process of removing substances from the cell by fusing internal vesicles with the cell membrane