Frank Baker, age 14, of Carson City, Nev., for his question:

JUST WHAT IS CHLOROPHYLL?

Chlorophyll is the pigment in plants that gives them their green color and that absorbs the light necessary for photosynthesis, the chemical reaction that converts light energy to chemical energy.

The great abundance of chlorophyll in leaves and its occasional presence in other plant tissues, such as stems, causes these plant parts to appear green.

Chlorophyll is a large molecule composed mostly of carbon and hydrogen. At the center of the molecule is a single atom of magnesium surrounded by a nitrogen containing group of atoms called a porphyrin ring. A long chain of carbon and hydrogen atoms proceeds from this central core and attaches the chlorophyll molecule to the inner membrane of the chloroplast, the cell organelle, in which photosynthesis takes place.

As a molecule of chlorophyll absorbs a photon of light, its electrons become excited and move to higher energy levels. This initiates a complex series of chemical reactions in the chioroplast that enables the energy to be stored in chemical bonds.