PCB3743 Vertebrate Physiology Summer 2014 Exam #1 Study Guide 1 Exam 1 will be given Wednesday May 21 at 9:30am in King 1024 (usual time & place.) [Page numbers are given for both 13th edition and 12th edition of Fox; chapter, section and figure numbers are the same for both editions, I think.] Exam 1 will cover lectures 1-7, Fox Chapters: 6, 7, 12 and 8. The exams will cover the topics discussed in lecture, with additional details drawn from the textbook chapters. Topics not covered in lecture will not be on the exam (as noted below). Remember that the lecture slides and recordings of the lectures are posted for your review on Blackboard. The exam format will be ~60 multiple choice/ fill in the blank/matching questions, using scantronics forms. You will have 75 minutes (the full lecture period) to complete the exam. Membrane Transport (Lecture 1, Chapter 6) 1. Understand the processes of diffusion and osmosis Diffusion: Due to random movement (thermal energy), solute molecules will show net movement from a region of high concentration to a region of low concentration • Solute moves down its concentration gradient • High solute concentration low solute concentration • The rate of diffusion… o Increases with temperature o Increases with concentration gradient o Increases with surface area of membrane o Decreases with distance • Diffusion is only efficient at 100 µm or less • If the solute molecules can penetrate the membrane, diffusion can occur o Nonpolar molecules Lipids & steroids o Small gas molecules – O2 & CO2 O2 diffuses into cell CO2 diffuses out of cell o Ions Can move down concentration gradient through protein channels in the membrane • Channels must be openPCB3743 Vertebrate Physiology Summer 2014 Exam #1 Study Guide 2 Osmosis: Diffusion of water across a semipermeable membrane (through aquaporin channels) from a solution with a low solute concentration to a solution with a high solute concentration • Water moves down its concentration gradient – from a region of high water concentration to a region of low water concentration o The region with a higher solute concentration is less dilute (has less water) o The region with a lower solute concentration is more dilute (has more water) • Water will continue to diffuse across the membrane until… o The solute concentration is the same on both sides of the membranePCB3743 Vertebrate Physiology Summer 2014 Exam #1 Study Guide 3 o Physical pressure stops the flow • Osmotic Pressure: A measure of the force required to stop osmosis that indicates how strongly a solution draws water by osmosis o The greater the solute concentration of a solution, the greater its osmotic pressure More solutes = more pressure o Pure water has an osmotic pressure = zero (0) • Isotonic: Equal osmotic concentration on each side of the membrane • Hypotonic: Less concentrated solution & lower osmotic pressure o Ex) Distilled water • Hypertonic: More concentrated solution & higher osmotic pressure o Ex) Seawater • Osmolality (Osm): The osmotic concentration of a solution, determined by the number of particles in the solution o Osmolality (Osm) = # of particles in moles / Liter of water 2. What are the mechanisms of carrier-protein mediated transport across the cell membrane? Properties of Carrier Mediated Transport: • Carrier proteins interact only with specific molecules o Ex) Glucose transporters transport glucose, but not fructose • As the concentration of a transported molecule is increased, its rate of transport will also increase, but only up to a transport maximum (Tm) o Concentrations greater than the transport maximum do not produce further increase in the transport rate Indicates the carrier transport is saturated • Closely related molecules can compete for transporters on the cell surfacePCB3743 Vertebrate Physiology Summer 2014 Exam #1 Study Guide 4 o Two molecules that are transported by the same carrier compete with each other The rate of transport for each is lower when they are present together than it would be if each were present alone Facilitated Diffusion: Transported molecule is moved down its concentration gradient with no extra energy (ATP) required • Uses potential energy of the concentration gradient • Ex) Diffusion of glucose from the blood across plasma membranes o GLUT: Glucose transporter o Requires using a limited number of transporters o Transport can be regulated by increasing or decreasing the number of transportersPCB3743 Vertebrate Physiology Summer 2014 Exam #1 Study Guide 5 Active Transport: Movement of molecules and ions against their concentration gradients from lower to higher concentrations • Primary Active Transport: Membrane carrier protein is an ATPase that breaks down ATP to release energy o Hydrolysis of ATP is directly responsible for the function of the carriers o Energy is used to transport the molecule against its concentration gradient o Ca2+ ATPase Pump: Hydrolysis of ATP & release of ADP causes conformational change in transporter, releasing Ca2+ outside the cell (into the extracellular fluid) o Na+/K+ ATPase Pump: 3 Na+ ions bind to inside of carrier protein ATP is hydrolyzed Release of ADP moves 3 Na+ to outside of cell Release of Pi moves 2 K+ inside of cell 3 Na+ out & 2 K+ in for every 1 ATP moleculePCB3743 Vertebrate Physiology Summer 2014 Exam #1 Study Guide 6 • Secondary Active Transport / Coupled Transport: The energy needed for the “uphill” movement of a molecule or ion is obtained from the “downhill” transport of another molecule into the cell o Cell uses energy to establish steep concentration gradient for molecule 1 Ex) Use Na+/K+ ATPase pump to set high [Na+] outside of cell o Co-transporter allows molecule 1 to move down its concentration gradient o Couples energy of first molecule to co-transport molecule 2 up (against) its gradient Ex) Concentrate glucose inside cell o Cotransport/Symport: Both molecules move in same direction Ex) Na+ & glucose move into cell simultaneously o Countertransport/Antiport: Molecules move in opposite directions One molecule moves into the cell while the other molecule moves out of the cellPCB3743 Vertebrate Physiology Summer 2014 Exam #1 Study Guide 7 Bulk Transport: Transport of molecules (i.e. polypeptides & proteins) that are too large
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