Answer
In an animal cell, energy comes from molecules transported to that cell and broken down via cellular respiration. That process produces ATP. The energy in an animal cell, carried in the form of ATP, can be used to drive all kinds of biosynthetic reactions, catalyzed/sped up by the many enzymes in a cell which lower reactions' activation energies. While the same can be true of a plant cell at times, at least some of the time a plant cell can capture the energy in light via photosynthesis for itself, making ATP in that way as well as by cellular respiration.
Work Step by Step
The key to getting to this answer is to see that animal cells break down molecules brought to them and that they must rely on cellular respiration for obtaining energy. In contrast, plant cells can use cellular respiration or photosynthesis, but the most common energy currency in either case is ATP. This can be used to drive non-spontaneous reactions by coupling ATP hydrolysis to those other reactions, and enzymes can help in the coupling and in speeding up reactions.
