USMLE Step 1: Physiology Exocytosis Exocytosis is the process by which macromolecules are packaged in secretory vesicles and then extruded from the cell. This process requires both calcium and energy Constitutive secretion: The vesicles are not coated with clathrin and are continuously fusing with the cell membrane. Regulated exocytosis: The vesicles are coated with clathrin, and a signal is required before the vesicle will fuse with the membrane, (e.g, the release of vesicular-bound water-soluble hormones Graphical Representation of Transport Processes One method of testing your understanding of physiologic process is by presenting a graph to interpret, Figure 1-1-5 and the accompanying questions test your understanding of membrane transport. The graph simply represents extracellular concentration versus rate of transport across the cell membrane Flux Into Extracellular Review Questions The following questions refer to Figure I-1-5 (answers with explanations on the next page) 1. Which curves could represent simple diffusion? If the surface area for diffusion increased what would happen to the slope of the diffusion curve? 2. Which curves could represent protein-mediated transport? Could you separate active transport versus facilitated transport curves? 3. Which curves demonstrate a TM? Which curve has the lowest TM, and which curve has the greatest TM? 4. If"C "represents the movement of glucose into skeletal muscle under control conditions. which curve would represent glucose transport after adding additional insulin? What does insulin do to the number of functioning transporters in the system?/" USMLE Step 1: Physiology 8 meilical Exocytosis Exocytosis is the process by which macromolecules are packaged in secretory vesicles and then extruded from the cell. This process requires both calcium and energy. Constitutive secretion: The vesicles are not coated with clathrin and are continuously fusing with the cell membrane. Regulated exocytosis: The vesicles are coated with clathrin, and a signal is required before the vesicle will fuse with the membrane, (e.g., the release of vesicular-bound water-soluble hormones). GraphicalRepresentationof TransportProcesses One method of testing your understanding of physiologic process is by presenting a graph to interpret. Figure 1-1-5 and the accompanying questions test your understanding of membrane transport. The graph simply represents extracellular concentration versus rate of transport across the cell membrane. A Flux Into Cell D B C Extracellular Concentration Figure 1-1-5 ReviewQuestions The following questions refer to Figure 1-1-5: (answers with explanations on the next page) 1. Which curves could represent simple diffusion? If the surface area for dfffusion increased, what would happen to the slope of the diffusion curve? Which curves could represent protein-mediated transport? Could you separate active transport versus facilitated transport curves? 2. 3. Which curves demonstrate aT M?Which curve has the lowest TM' and which curve has the greatest TM? If "c" represents the movement of glucose into skeletal muscle under control conditions, which curve would represent glucose transport after adding additional insulin? What does insulin do to the number of functioning transporters in the system? 4