In the urea cycle, the carbon skeleton of aspartate is preserved as a) succinate b) fumarate. c) urea. d) e) all of the above. none of the above

Spontaneity tell us the direction of the reaction, but not how fast it goes. gibbs free energy brings together enthalpy, entropy and temperature in one easy formula. g = h - ts. and, finally the sign of delta g is always negative for a spontaneous reaction.