Final answer:
Enzymes are not consumed in reactions, they lower activation energy, and are specific to substrates. They can be denatured by extreme conditions.
Step-by-step explanation:
Enzymes are biological catalysts that lower the activation energy of chemical reactions. They are not consumed in reactions but can be used over and over again. Enzymes are highly specific to the substrates they interact with, binding to them at a site called the active site on the enzyme molecule. Extreme conditions can denature enzymes, altering their structure and therefore their function.