Final answer:
Enzymes are specific catalysts that speed up metabolic processes by lowering activation energy and can be reused after reactions; they also change shape for substrate binding.
Step-by-step explanation:
The true statement about enzymes is that they can speed up metabolic processes in the body. Enzymes achieve this by acting as biological catalysts that lower the activation energy of reactions. They are highly specific and do not act on nonspecific, randomly chosen substrates. Contrary to being single-use, after a reaction enzymes can be reused as they are not consumed in the reactions they catalyze. Lastly, enzymes can and do often change shape, undergoing conformational changes upon substrate binding based on the induced fit model.