1) To survive, the organism shown below needs to concentrate glucose as an energ
ID: 193392 • Letter: 1
Question
1) To survive, the organism shown below needs to concentrate glucose as an energy source by using the glucose sodium symporter shown. Calculate the free energy change associated with this system using the concentrations and elecrical potential provided below. (T = 298.15 K, R = 8.314 J.K"mol.-1, F-96480 J-v1mol..! G = RT In Q + ZFAp ) Glcloutside mM: Nuside 100 mM IGlnsid 10 mM: INatnside 10 mM Aup =-100 mV 2 Na+ 2 Na Gle Why is this process favorable? How does the transporter stoichiometry affect the free energy change?Explanation / Answer
a) The concentration of glucose is higher inside (10mM) compared to outside (1mM), still glucose is transported outside to inside. Indeed it an unfavorable reaction transport because it is against the concentration gradient and is an active transport which occurs by sodium-glucose symporter. The question is where from it gets this energy? The answer is that this is an indirect active transport. Actually Na-K+ pump is used to create a gradient actively using the ATP, where concentration of Na+ is kept high outside compared to inside. Then the Na+ when transported from the higher concentration (outside) to lower concentration (inside), it releases energy and that energy makes this transport favorable. In conclusion this is an indirect transport made favorable by concentration gradient of Na+ which in turn created by active Na-K+ pump.
b) The relative concentration of sodium, K+ and glucose taking part in in the primary and secondary active transport .affect the free energy change. As already mentioned the energy is stored in the conc. gradient of Na+-K+ by primary active transport. Therefore, when sodium falls from high to low concentration via sodium-glucose secondary symporter, diffusion of sodium occurs, since it is from higher to lower free energy, it gives energy and that energy is utilized by this transporter to drive glucose inside the cell against concentration gradient by active transport.
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