Virtually every chemical reaction in a cell occurs at a significant rate only because of the presence of enzymes. - Albert L. Lehninger

Cells of all kinds share certain structural features.

Perhaps the most remarkable property of living cells and organisms is their ability to reproduce themselves for countless generations with nearly perfect fidelity. This continuity of inherited traits implies constancy, over millions of years, in the structure of the molecules that contain the genetic information.

The distinguishing characteristics of eukary­otes are the nucleus and a variety of membrane-enclosed organelles with specific functions.