CHAPTER 3 MOVEMENTS THROUGH THE CELL MEMBRANE

PASSIVE MECHANISMS  Higher concentration to lower concentration  No energy required  4 Types: Diffusion, Facilitated Diffusion, Osmosis, and Filtration

Diffusion  Higher to lower concentration  No energy required  Random movement of molecules  Example: Oxygen & carbon dioxide exchanged between blood & alveoli  Example: Molecules of sugar passing through membrane to replenish cell’s lack of sugar  Diffusion through cell membrane Diffusion through cell membrane

FACILITATED DIFFUSION  Higher to lower concentration  No energy required  Sugars & lipids too large to pass through membrane so glucose binds w/protein carrier to go across  Shape of carrier changes and glucose moves to other side of membrane & is released

Osmosis  Higher to lower concentration  No energy required  Special type of diffusion  Passing of Water molecules only!!  Osmotic Pressure: Ability of osmosis to lift a volume of water  Example: Plant is wilting so you water it- water passes through by osmosis

OSMOSIS  3 Types of Solutions:  Isotonic: Any solution that has the same osmotic pressure as the body’s fluids  Hypertonic: Solutions w/higher osmotic pressure than body fluids-water moves out of cells into surrounding solution-cells shrink  Hypotonic: Solutions w/lower osmotic pressure than body fluids-cells gain water & swell

FILTRATION  Higher to lower concentration  No energy required  Forces molecules through membrane-forced by Hydrostatic Pressure that is greater on one side than the other  Separates solids from water  Example: Blood Pressure is greater w/in blood vessel than outside it so smaller molecules leave through capillary walls-larger molecules stay inside

ACTIVE MECHANISMS  LOWER TO HIGHER CONCENTRATIONS  ENERGY REQUIRED  3 TYPES: Active transport, endocytosis, and exocytosis

ACTIVE TRANSPORT  Lower to higher concentration  Energy is required  Carrier molecules are Proteins with binding sites They combine w/what needs to be transported Energy is released Carrier protein shape changes Particle moves across membrane  Ex. Sugars, a.a., Na, K, Ca do this

ENDOCYTOSIS  Lower to higher concentration  Energy is required  Uses cellular energy to move substances into cell w/o actually crossing membrane-uses vescicles  2 Types: Pinocytosis: Takes in liquids by way of vescicles Phagocytosis: Takes in solids by way of vescicles Phagocytosis

EXOCYTOSIS  Lower to higher concentration  Energy is required  Uses cellular energy to move substances out of the cell  Example: Cells getting rid of waste material