Julie Smith, age 15, of Monroe, La., for her question:

WHAT IS MOLECULAR BIOLOGY?

Molecular biology is the study of the structure and function of the large molecules essential to life. Among these molecules are proteins and nucleic acids. Proteins catalyze or speed up chemical reactions that supply the energy for living cells while nucleic acids carry the genetic code necessary for the development of all living cells.

Molecular biologists try to find out how these molecules are built and how they work. They use X rays, electron microscopes and chemical methods that purify and break down molecules for their studies.

Scientists in this field want to learn how proteins are made in a cell and how they work. They hope to discover how single germ cells can grow into complex organisms such as humans, animals and plants.

Molecular biologists also hope to find out exactly how the brain works.