Lecture_6_Jan_15_four_slides_per_page_

Lecture_6_Jan_15_four_slides_per_page_ - two types of...

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1 Functions of Membrane Transport o ingest essential nutrients • To ingest essential nutrients • To excrete metabolic waste or toxic products o reg late intracell lar composition • To regulate intracellular composition two types of membrane transport protein-mediated non-protein mediated (simple diffusion) energy required (active transport) no energy input required (passive transport) no energy input required (passive transport) two types of proteins involved in membrane transport protein-mediated transport Channels (to be discussed next time) Transporters (Carriers, Permeases) (to be discussed today) Five General Considerations for Membrane Transport Whether is energy required for a transport process? If energy is not needed, whether is a protein needed? If energy is needed (a protein is also needed in this case), what is the source of energy? ions are moved across the membrane how to maintain the If ions are moved across the membrane, how to maintain the electrical neutrality of a cell or compartment? If H + or OH - are moved across the membrane, how to maintain the pH of a cell or compartment?
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2 two types of membrane transport protein-mediated non-protein mediated (simple diffusion) energy required (active transport) no energy input required (passive transport) no energy input required (passive transport) For passive transport, whether simple diffusion or protein-mediated transport is utilized depends on the nature of molecules to be transported Transporters reading assignment: for 4 th ed: 615-626 for 5 th ed: 651-663 Transporters (Carriers, Permeases) bind a specific solute to be transported on one side of a membrane release the specific solute on the other side of a membrane conformational changes (weak binding) (strong binding) (g ) 1. the binding between a transporter & its solute is usually strong on one side and weaker on the other side 2. the binding is saturable due to limited binding sites (see the next slide) and a transporter can only bind one or few solute molecules at one time 3. each transport cycle takes some time 4. as a result of 2 and 3, a transporter works relatively slowly (1-1000 molecules/sec) 5.
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This note was uploaded on 02/01/2010 for the course MCDB 103 taught by Professor Staff during the Winter '08 term at UCSB.

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Lecture_6_Jan_15_four_slides_per_page_ - two types of...

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