Greg Samuelson, age 12, of Akron, Ohio, for his question:

HOW MANY TYPES OF ENZYMES ARE THERE IN THE BODY?

An enzyme is a protein molecule that speeds up chemical reactions in all plants and animals. Without enzymes, these reactions would occur too slowly or not at all, and no life would be possible.

The human body contains more than 1,000 types of enzymes. Each kind performs one specific job. Without enzymes, a person would not be able to see, breathe, digest food or move any part of his body.

Many enzymes break down complex substances into simpler ones. Others build complex compounds from simple ones. Enzymes serve as catalysts. A single enzyme molecule can perform its entire function a million times a minute.