Exam 2 ReviewTransport Give examples of different forms of facilitated diffusion (passive transport, conc. gradient) that allow the movements of molecules through. Discuss the selectivity of each type of translocator and contrast the structural differences of each class of translocators.a) an aqueous channel, or Extend across lipid bilayer- Allow movements of specific molecules- Composed of beta sheets and alpha helicies- Glycerol, straight chain sugars, urea, glycine- Ex/ glycerol porin- Has a polar pore and non polar exterior that interacts with membraneb) via a carrier. Aka transporters, bind the specific solute Undergo conformational changes to transfer across membrane When transporter is saturated (binding sites are occupied) rate of transport Vmax is highest Each transporter has a characteristic affinity for its colute, Km, which = conc. Of solute when transport rate V is half maximum falue (Km= ½ Vmax) Binding site can be blocked by inhibitors- Ex/ glucose 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?- Facilitated diffusion- shows leveling off of glycine, doesn’t continuously flow in- Simple diffusion- linear, continuously flows in at constant speed- Mix glycine and methionine together, they start diffusing through membrane, but if they are using the same carrier they are competing to diffuse,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?- Theyre using the same channel, so if Ecoli has a mutation, it’s aqueous channel, or porin is altered and the uptake of glycerol and urea is effected What are aquaporins? Describe the basic two-dimensional and three-dimensional structural features of a typical aquaporin.- Aquaporin- are proteins embedded in the cell membrane that regulate the flow of water, abundant in epithelial cells of kidney- 6 membrane spanning domains/ alpha helices (in green), form wall of cylinder, core provides channel- 28 KD- amino and carboxylic ends on cystolic sugar chain that goes out into extracellular space-What are the differences between primary and secondary forms of active transport? Illustrate with an example in each case. (ch 11 pg. 656)- primary- ATP broken down to functiono electrogenic pump- voltage in cell will be more negative, voltage allows for more energy, ATPo J. Skou (1957)- investigating a type of enzyme w/ ATPase activity (ATP - ADP + Pi) – discovered presence of ion had effect on ATPaseo Na+ - K+ pump- Secondary- not ATP driven, ion-driven (by concentration gradient)o Glucose into intestinal cellso Symport w/ Na+ from high to low concentration, down electrochemical gradientContrast 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.- RBC- single direction (due to glycolysis)o Carrier- Small intestineo Secondary active transporto Na+ cotransporto Transcytosis aka transcellular transportoWhat 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 cultured adipocytes. High blood glucose, causes pancreas to secrete insulin – cell signaling molecule, causes fat cells to take up more glucose, GLUT4 receptors fuse w membranes to bring in more glucose, fluorescence in GLUT4 w insulin moved everything outwards to membrane Fluorescent tagWhat is the subunit composition of the mammalian Sodium-Potassium ATPase? Outline the catalytic cycle of that transporter (by showing the sequence of steps leading to the appropriate translocations of sodium and potassium across the membrane). Indicate the action of ouabain andshow the step it affects in the catalytic cycle of the enzyme. How about the Ca++ pump? For every molecule of ATP hydrolyzed inside cell, 3 Na+ are pumped out and 2 K+ are pumped in Ouabain- came from flowering plant in Africa, used as drug to help heart problemso Binds to extracellular protein, Beta subunit, in the E2P conformation where the 2K would bind (pump can’t eject Na+ or bring in K+)o Competes for se same site on the extracellular side of the pump as K+ Ca++ pump- in sarcoplasmic recticulum (SR) membrane of skeletal muscle cellso Forms a network of tubular sacs in muscle cell cytoplasm and serves as intrecellular store of Ca++o When action potential depolarizes muscle cell plasma membrane, Ca++ is released into cytosol from the SR through Ca++ release channels, stimulating muscle to contracto Moves Ca++ from cytosol back into SRo Binding of ATP to binding site on same side of membrane as terminal phosphate group leads to rearrangement of transmembrane helicies Disrupts Ca++ brinding cite and releases Ca++ ions on other side of membrane into lumen of SRWhy 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 ofthe 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 sodium- potassium ATPase in the process? Where on the cell’s membrane is each of the above carriers located? Intestinal cells- polarized, membrane on one side of cell has diff func then membrane on other side of cell Tight junctions seal so nothing can pass inbetween Proteins attach one membrane of once cell to anothero Claudin- claudin of one cell seals to claudin to anotherWhat would you include in an aqueous drink that you would administer to a severely dehydrated individual, such as one suffering from a cholera infection? Explain the reason behind the additionof each substance in the drink. Salt, sugar, and water Water- dehydrated Na causes you to store
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