a substrate binds to an enzyme at the active site, where the reaction occurs.
Stamen: The pollen producing part of a flower, usually with a slender filament supporting the anther. Anther: The part of the stamen where pollen is produced. Pistil: The ovule producing part of a flower. The ovary often supports a long style, topped by a stigma.
Chemical signal can signify the lymphatic, nervous and endocrine system.
Mostly endocrine, the endocrine system is the body system responsible for providing the needed hormones for the body. These hormones and body fluids contribute and catalyse the growth, disposition, sex characteristics and other potential corresponding output of these hormones.