Definition: Given a scientific passage and an answer, generate a question for the given answer.
Input: Passage: Chemical reactions constantly occur inside the cells of living things. However, under the conditions inside cells, most biochemical reactions would occur too slowly to maintain life. That's where enzymes come in. Enzymes are catalysts in living things. Like other catalysts, they speed up chemical reactions. Enzymes are proteins that are synthesized in the cells that need them, based on instructions encoded in the cells' DNA. Answer: enzymes
Output:
What proteins synthesized in cells act as catalysts?