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Hernandez Ramirez Juan Gibbs Free Energy exercises
1. Calculate the Gibbs Free Energy change (𝛥𝐺) for the following chemical reaction: ATP→ADP+Pi The reaction occurs at 68°F, the change in heat (𝛥𝐻)=19,070cal, and the change in entropy (𝛥𝑆)=90cal/K Change in Gibbs Free energy equation: 𝛥𝐺=𝛥𝐻−𝑇𝛥𝑆 Information: T=68°F=293°K 𝛥𝐻=19,070cal 𝛥𝑆=90𝑐𝑎𝑙/𝐾 Procedure: 𝛥𝐺=1,9070𝑐𝑎𝑙−293°𝐾( 𝑐𝑎𝑙 𝐾 )^ 𝛥𝐺=19,070𝑐𝑎𝑙−26,370𝑐𝑎𝑙 𝛥𝐺=−7,300𝑐𝑎𝑙 𝛥𝐺=− 7 , 300 𝑐𝑎𝑙 1 , 000
𝑘𝑐𝑎𝑙 𝑚𝑜𝑙 Conversion from 𝑘𝑐𝑎𝑙 𝑚𝑜𝑙
𝑘𝐽 𝑚𝑜𝑙 1
2. Calculate the Gibbs free energy change (𝛥𝐺) for the following chemical reaction: glutamate+𝑁𝐻3→glutamine+𝐻 2 𝑂 The reaction occurs at 68°F, the change in heat 𝛥𝐻=4,103cal, and the change in entropy 𝛥𝑆=2.4cal/K Information: T=68°F=293°K 𝛥𝐻=4,103cal 𝛥𝑆=2.4𝑐𝑎𝑙/𝐾 Procedure: 𝛥𝐺=4,103𝑐𝑎𝑙−293°𝐾( 2. 4 𝑐𝑎𝑙 𝐾
𝑐𝑎𝑙 1 , 000 =3.4𝑘^ 𝑐𝑎𝑙 𝑚𝑜𝑙 Conversion from 𝑘𝑐𝑎𝑙 𝑚𝑜𝑙
𝑘𝐽 𝑚𝑜𝑙 1kJ→0.239 kcal/mol 𝑥 =
Hernandez Ramirez Juan
3. Would either of the reactions above occur spontaneously? If so, which ones(s) and why? Yes, the first reaction (ATP → ADP+Pi). This is due to the spontaneous reactions take place when the values for 𝜟𝑯 and 𝜟𝑺 are positive, and the 𝜟𝑮 is negative ( 𝜟𝑮 < 𝟎) above all; however, it will be a spontaneous one at high temperatures. For this case, it is 293°K=19.85°C. 4. How does the Gibbs Free Energy in each of the two reactions change if the temperature were raised to normal body temperature (98.6°F)? Gibbs Free Energy change for the first reaction: 98.6°F=310°K 𝛥𝐺=19,070𝑐𝑎𝑙−310°𝐾(90𝑐𝑎𝑙𝐾) 𝛥𝐺=19,070𝑐𝑎𝑙−27,900𝑐𝑎𝑙 𝛥𝐺 = − 8 , 830 𝑐𝑎𝑙 = −
1kJ/mol→0.239 kcal/mol 𝑥 =
Gibbs Free Energy change for the second reaction: 𝛥𝐺 = 4,103𝑐𝑎𝑙 − 310°𝐾(2. 𝑐𝑎𝑙 𝐾
𝑐𝑎𝑙 1 , 000
𝑘𝑐𝑎𝑙 𝑚𝑜𝑙 Conversion from 𝑘𝑐𝑎𝑙 𝑚𝑜𝑙 to^ 𝑘𝐽 𝑚𝑜𝑙 1kJ/mol → 0.239 kcal/mol 𝑥 =
5. If the second reaction (glutamate+𝑁𝐻 3 →glutamine+𝐻 2 𝑂) is coupled to the first reaction (ATP→ADP+Pi), what will be the effect? Would that second reaction still be endergonic and nonspontaneous? Support your answer with the appropriate calculations. ( 2 )𝑔𝑙𝑢𝑡𝑎𝑚𝑎𝑡𝑒 + 𝑁𝐻 3 → 𝑔𝑙𝑢𝑡𝑎𝑚𝑖𝑛𝑒 + 𝐻 2 𝑂, 𝛥𝐺 = 3. 4
Sum: ATP+ glutamate+ 𝑁𝐻 3 →ADP+ glutamine+Pi Sum: - 30.54 kJ/mol+ 14.22 kJ/mol= - 16.32 kJ/mol The effect will be that the reaction becomes exergonic, and it is a spontaneous reaction too because of the 𝜟𝑮<𝟎. So, the second reaction will not be endergonic and nonspontaneous anymore.
