Agenda NOTES: Active Transport Simple & Facilitated Diffusion Protein Pumps Endocytosis & Exocytosis Osmosis Practice Problems (Friday Lab)
Passive Transport “Passive Transport” means that the cell can move molecules in and out of the cell without using energy Passive transport relies on diffusion that naturally moves substances from high to low concentration There are 2 types of diffusion: Simple Diffusion Facilitated Diffusion
Simple Diffusion In simple diffusion, molecules pass directly through the membrane by slipping between phospholipids Simple diffusion is possible under 2 conditions: The molecule is small The molecule has no electric charge
Ions An ion is an atom or molecule that carries an electric charge. Ions may be either + or - . Ions can’t pass through a membrane because the non-polar “tails” repel charges. Salt is Ionic: Salt is made of Sodium [Na] and Chlorine [Cl]. When salt dissolves in water the Sodium becomes positive and the chlorine becomes negative.
Facilitated Diffusion Large molecules and ions can diffuse in and out of the cell by going through protein channels (tunnels). Each protein channel is shaped to work for only one specific molecule.
Active Transport In Active Transport, the cell uses energy to move substances through the membrane. This energy comes in the form of ATP molecules that are produced by mitochondria breaking down food. There are 3 types of active transport: Protein Pumps Endocytosis Exocytosis
Protein Pumps Protein Pumps use ATP energy to change their shape and force molecules in or out of the cell. Protein pumps can work against the direction of diffusion, allowing cells to maintain high concentrations of important substances.
Endocytosis Endocytosis brings a large number of molecules into the cell. Endocytosis begins with the membrane bulging inward to create a small pocket. The pocket pinches inward and forms a bubble (vesicle) inside of the cell.
Exocytosis Exocytosis removes a number of molecules from the cell. During exocytosis, a tiny bubble (vesicle) will join to the membrane and release the substances it carries to the outside.