Essential Cell Biology 5th edition

CHAPTER TWO
2
Chemical Components of Cells
At first sight, it is difficult to comprehend that living creatures are merely
chemical systems. Their incredible diversity of form, their seemingly purposeful
behavior, and their ability to grow and reproduce all seem to set
them apart from the world of solids, liquids, and gases that chemistry normally
describes. Indeed, until the late nineteenth century, it was widely
believed that all living things contained a vital force—an “animus”—that
was responsible for their distinctive properties.
CHEMICAL BONDS
SMALL MOLECULES IN CELLS
MACROMOLECULES IN CELLS
We now know that there is nothing in a living organism that disobeys
chemical or physical laws. However, the chemistry of life is indeed a
special kind. First, it is based overwhelmingly on carbon compounds, the
study of which is known as organic chemistry. Second, it depends almost
exclusively on chemical reactions that take place in a watery, or aqueous,
environment and in the relatively narrow range of temperatures experienced
on Earth. Third, it is enormously complex: even the simplest cell is
vastly more complicated in its chemistry than any other chemical system
known. Fourth, it is dominated and coordinated by collections of large
polymers—molecules made of many chemical subunits linked end-toend—whose
unique properties enable cells and organisms to grow and
reproduce and to do all the other things that are characteristic of life.
Finally, the chemistry of life is tightly regulated: cells deploy a wide variety
of mechanisms to make sure that each of their chemical reactions
occurs at the proper rate, time, and place.
Because chemistry lies at the heart of all biology, in this chapter, we briefly
survey the chemistry of the living cell. We will meet the molecules from
which cells are made and examine their structures, shapes, and chemical
properties. These molecules determine the size, structure, and functions