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# Membrane Transport Mechanism ## L7 BIO 101 Energy * Needed for cell growth and normal activities. To utilize the compounds, cells must uptake nutrients from the environment. * Uptake mechanisms must be specific- that is the necessary substances, not others, must be acquired. So, special transp...
# Membrane Transport Mechanism ## L7 BIO 101 Energy * Needed for cell growth and normal activities. To utilize the compounds, cells must uptake nutrients from the environment. * Uptake mechanisms must be specific- that is the necessary substances, not others, must be acquired. So, special transport systems are required for nutrient uptake. * Transport systems are located in the cytoplasmic membrane, a selectively permeable membrane. To enter the cell, nutrients must cross the other layer of cell. ### Types of transport system - Diffusion across lipid bilayer - Passive transport - Active transport ## Passive Transport * Flow of solutes through the interior of the passive transport proteins down their concentration gradients. (From a high to low concentration) * Passive transport proteins allow solutes to move both ways. * Does not require any energy input. ## Active Transport * Movement of molecules from an area of lower concentration to the area of higher concentration (against concentration gradient). * Transport protein must be activated. * ATP gives up phosphate to activate transport protein. * Binding of phosphate changes transport protein shape and affinity for solute. * The other side opens, solute is released. * Removal of phosphate * Protein goes back to its original state
