Question

specific part of an enzyme where a substrate fits sucrase how do enzymes speed up chemical reactions? active site acid

Explanation:

The question is about the specific part of an enzyme where a substrate fits. Sucrase is an enzyme (not the part where substrate fits), "How do enzymes speed up chemical reactions?" is a question (not a structure), and acid is a substance (not related to enzyme - substrate fitting). The active site is defined as the specific region of an enzyme where the substrate binds and the reaction occurs.

Answer:

Green. Active Site