Karyotype How would you screen a sample of cells obtained from an individual for potential chromosomal abnormalities using karyotype analysis Transport Give examples of different forms of facilitated diffusion that allow the movements of molecules through a an aqueous channel gylcerol porin aquaporin b carrier glucose translocator protein GLUT1 GLUT2 GLUT3 GLUT4 GLUT5 compound specific Discuss the selectivity of each type of translocator and contrast the structural differences of each class of translocators Porin has polar center and non polar exterior that interacts with the membrane Glycerol channel aquaporins have 6 membrane spanning domains that form the wall of the cylinder alpha helices Core of cylinder provides the channel 2 helices one dangles from the top and one dangles from the bottom these are selectivity loops Glucose transporters GLUT 1 5 12 helices and hydrophobic pocket How would you determine whether the transport of the amino acid glycine into red blood cells occurs by simple diffusion or by facilitated diffusion If glycine were to be imported by facilitated diffusion how could you determine whether or not another amino acid such as methionine moves into the cells by the same carrier Simple diffusion is a linear diffusion and continuously at consistent pace Facilitated diffusion would show a leveling off of the glycine Put glycine and other amino acid together at same time If they use the same carrier there would be more competition so less glycine would enter the cell and the saturation time would lower There would be no change if they are not the same carrier Why might a single mutation in E coli result in simultaneous altered movements of glycerol a four carbon sugar and urea through the cell s membrane They use the same porin channel so the expression would be altered for glycerol four carbon sugar and urea What are aquaporins Describe the basic two dimensional and three dimensional structural features of a typical aquaporin Aquaporin is the movement of water Cross lipid bilayer 6 times selectivity loops at B and E amino acids at selectivity loops Selectivity loops inside lipid bilayer 28 kDa molecular weight Amino and carboxylic ends on cytosolic side Common to have sugar chain that moves out into extracellular space What are the differences between primary and secondary forms of active transport Illustrate with an example in each case Primary is when you use ATP for transport Examples Na K ATPase J Skou used electrogenic pump to discover prescence of ions had effect on ATPase Secondary is glucose into intestinal cell symport with sodium from high to low concentration ion driven when sodium calcium exchange brings in glucose Contrast the mechanism of transport of glucose from the blood into a red blood cell with the transport of glucose from the lumen of the small intestine into intestinal epithelial cells Glucose from blood into red blood cells single direction due to glycolysis glucose is immediately transformed into pyruvate GLUT6 phosphate then used by red cell doesn t leave Glucose lumen of small intestine into intestinal epithelial cells secondary active transport coupled with Na transcytosis pass through cell high concentration of Na in intestine and low Na in intestinal cell so it moves through gradient Experiment Leucite tube through tissue of intestine and chamber on one end of chamber have Na and radioactive glucose Glucose can be seen to move with the Na What are the molecular features of the glucose transporter subunit in facilitated diffusion What is the mechanism responsible for the increased capacity of adipocytes to transport glucose from the blood in response to an elevation in the concentration of blood insulin Give the details Outline the study discussed in lecture that demonstrated the phenomenon using cultures adipocytes When insulin is increased causes cells to release GLUT4 vesicles and those fuse with the membrane to allow more glucose to be taken up This occurs in response to high amounts of glucose outside of the cell Study Flourescent tag on GLUT4 receptor high density ball of receptors in middle then form a ring around outside of cell can see flourescent ring which shows that GLUT4 is used to bring glucose into the cell To achieve normal levels Low blood glucose then glucagon released by alpha cells of pancreas then liver releases glucose into the blood High blood glucose then insulin released by beta cells of pancreas then fat cells take up glucose from blood What is the subunit composition of the mammalian Sodium Potassium ATPase Outline the catalytic cycle of the transporter by showing the sequence of steps leading to the appropriate translocations of sodium and potassium across the membrane Indicate the action of ouabain and show the step it affects in the catalytic cycle of zthe enzyme How about the Ca pump Alpha subunit 10 membrane spanning in cytoplasm and Beta subunit 1 membrane spanning in extracellular Three sites in cytoplasm that bind Na Then protein conformation and ATP ADP Pi Conformation loses affinity for Na and it is released E2P conformation is outside and exposes two sites for K to bind to K binds and H2O and moves inside Pi falls off and ATP ADP occurs so K goes inside Ouabain binds to beta subunit extracellular cell and inhibits activity binds at E2P wheere K would bind and prevents pump from working so Na can t move out and K can t move in Used as drug to help with heart ailments Why are glycosides helpful to some patients suffering from atrial fibrillations How is the movement of glucose from the intestinal lumen to the blood accomplished in an intestinal epithelial cell Give the general structural features of the cell including a description of the tight junctions When in the process does the movement of glucose occur by a secondary active transport and when does it occur by facilitated diffusion What is the role of the Na K ATPase in the process Where on the cell s membrane is each of the above carriers located Secondary active transport at top with Na moving through and glucose passing with it Facilitated diffusion of glucose through the cell The Na K ATPase role is to maintain the gradient of low Na inside the cell so that secondary active transport can occur What would you include in an aqueous drink that you would administer to a severely dehydrated individual such as one suffering from cholera infection Explain the reason behind the addition of each substrate in the drink Salt sugar and water Na
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