Membrane Transport nswers Answer: A. It is a straight-line relationship: the greater the concentration gradient, the greater the rate of diffusion. If the surface area for diffusion increased, the slope would increase. This means that at a given concentration gradient the rate of diffusion would be would represent facilitated transport versus active transport. Facilitated transport is always down a concentration gradient, whereas active transport can be against a concen- tration gradient. This information is not presented in the graph 3. Answers: B, C, D. Again, this is a characteristic of all protein-mediated transport. TM is the rate of transport of the plateau(measured on the y axis). D has the lowest TM and B the greatest 4. Answer: B. Insulin simply places more transporters in the membrane system, which would increase T Chapter Summary A cell membrane is a lipid bilayer composed mainly of phospholipid Dynamic propenies are due to the protein component, which includes pumps, channels, receptors, and carriers Simple diffusion and facilitated transport are both passive processes(not energy-dependent) driven by concentration gradients. The rate of protein-mediated transport will increase with increased substrate delivery until the carriers are saturated. The maximum rate(camer saturation)is called TM, and this rate is directly proportional to the number of functioning carriers present in the system Secondary active transport is driven by the sodium gradient across the cell membrane, which is maintained by the Na/K-ATPase pump Endocytosis and exocytosis represent acive uptake and extrusion of macromolecules via vesicular medical 9, MembraneTransport Answers 1. Answer: A. It is a straight-line relationship: the greater the concentration gradient, the greater the rate of diffusion. If the surface area for diffusion increased, the slope would increase. This means that at a given concentration gradient the rate of diffusion would be greater. 2. Answers: B, C, D. These three curves demonstrate saturation kinetics (plateau), which is a characteristic of all protein-mediated transport. You cannot determine which curves would represent facilitated transport versus active transport. Facilitated transport is always down a concentration gradient, whereas active transport can be against a concen￾tration gradient. This information is not presented in the graph. 3. Answers: B, C, D. Again, this is a characteristic of all protein-mediated transport. TMis the rate of transport of the plateau (measured on the y axis). D has the lowest TMand B the greatest. 4. Answer: B. Insulin simply places more transporters in the membrane system, which would increase TM' ChapterSummary isalipidbilayercomposedmainlyof phospholipid.Dynamicpropertiesaredueto the proteincomponent,whichincludespumps,channels,receptors,andcarriers. Simplediffusionandfacilitatedtransportarebothpassiveprocesses(notenergy-dependent)drivenby concentrationgradients. Therateofprotein-mediatedtransportwillincreasewithincreasedsubstratedeliveryuntilthecarriers aresaturated.Themaximumrate(carriersaturation)iscalledTM'andthisrateisdirectlyproportionalto thenumberoffunctioningcarrierspresentinthesystem. Secondaryactivetransportisdrivenbythesodiumgradientacrossthecellmembrane,whichis maintainedbytheNajK-ATPasepump. Endocytosisandexocytosisrepresentactiveuptakeandextrusionofmacromoleculesviavesicular transport. mettical 9