Cell Transport Cell Membrane • Location of Cell Transport • Controls what enters and exits the cell • Made of 2 layers of phospholipids • Hydrophilic exterior • Hydrophobic interior • Embedded with proteins Cell Transport • Cell Transport – the passage of a substance through the cell membrane • 2 types • Passive Transport • Active Transport Passive transport • Passive transport – movement of a substance through the cell membrane without the use of energy • Occurs when substances move from a high concentration area to a low concentration area • This process is called Diffusion • 2 types Passive transport – Simple diffusion • Simple Diffusion – When a substance diffuses through a cell membrane without help from other molecules • Very small molecules squeeze between phospholipid molecules • Oxygen (O2) and carbon dioxide (CO2) are examples of molecules that can cross cell membranes this way. Passive Transport – Facilitated Diffusion • Facilitated Diffusion – Diffusion across the cell membrane with the assistance of transport proteins • 2 types of transport proteins • Channel protein – creates a tiny hole in the membrane to allow hydrophilic molecules through (water) • Carrier protein – binds with large molecules to allow them to pass through Active Transport – occurs when a substance passes through the cell membrane with the help of energy Active Transport From an area of low concentration to an area of high concentration • Opposite direction of diffusion Energy comes from ATP 2 main types Active Transport - Protein Pumps • Protein pumps – special transport proteins which use energy to transport substances to areas of higher concentration • EX: SodiumPotassium Pump • Energy is used to push sodium outside the cell and potassium is pulled into the cell Used with substances too large to be pumped across the cell membrane Active Transport – Vesicle Transport Uses energy to occur Exocytosis – vesicle transports substances out of the cell Endocytosis – vesicle transport substances into the cell
