quiz 7 key spring 2010

# quiz 7 key spring 2010 - Δ G = 6.42 kJ/mol-4.83 kJ/mol Δ...

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Consider a cotransporter that couples the transport of one leucine molecule to the transport of one Na+ ion. Given the following conditions: Temperature 310 K membrane potential ( Δ V) -50 mV pH 7 Solute Intracellular concentration Extracellular concentration leucine 33 mM 1 mM Na+ 12 mM 145 mM R = 8.314 J/(mol)(K) F = 96,500 J/(mol)(V) 1. 3 pts Calculate the energy cost (i.e. free energy change) of transporting leucine into the cell. Δ G = RTln(c2/c1) Δ G = (8.314 J/molK)(310 K)ln(33 mM/1 mM) Δ G = 9.01 kJ/mol Credit: 1 pt for correct equation (OK if includes membrane potential term); 1 point for correct identification of C2 and C1; 1 point for correct answer with units 2. 3 pt Calculate the free energy change associated with transporting Na+ into the cell Δ G = RTln(c2/c1) + ZF Δ V Δ G = (8.314 J/mol K)(310 K)ln(12 mM/145 mM) + (1)(96500 J/molV)(-0.05 V)
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Unformatted text preview: Δ G = - 6.42 kJ/mol + (-4.83 kJ/mol) Δ G = - 11.25 kJ/mol Credit: 1 pt for correct equation (must includes membrane potential term); 1 point for correct identification of C2 and C1; 1 point for correct answer with units 3. 2 pts. Based on your calculations above, is it energetically favorable to couple the transport of leucine into the cell with the transport of Na+ into the cell. Why or why not? Yes, because the overall Δ G for the coupled transport is negative Credit: 1 pt for correct answer, 1 pt for correct reason. Please give credit based on the student’s answers to parts 1 and 2 4. 2 pts. Is this antiport, symport, or uniport? Symport ( 1 pt) because Na+ and Leucine are both moving into the cell (same direction) ( 1 pt)...
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