10-1 How Does Energy Behave in the Universe?
supply of energy to stay alive. That energy ultimately comes from
the sun. If we fail to replenish the energy that we use, we die and
slowly deteriorate until the differences between us and our
For many centuries, it was believed that the energy of life was
somehow different from other forms of energy in the universe. Life
was defined and characterized by the existence of a special
. It was mistakenly believed that the vital force followed its
own set of rules, different from the rules that govern the flow of
energy in the inanimate world. We now recognize that energy, in
all its various forms, is the same in both the living and nonliving
worlds. The rules that govern energy apply universally. In this
chapter, we will examine what those rules are and how the
chemistry of life has evolved to capture and use energy without
breaking the rules.
How Does Energy Behave in the Universe?
Can you distinguish between something that is alive and something that is not? The
question may seem trivial at first. Of course animals breathe, move, eat, and reproduce—
all things that inanimate objects cannot do.When they cease to be alive, those activities
also cease. Plants grow, reproduce, absorb sunlight, consume carbon dioxide, and turn it
into complex carbohydrates.They, too, are clearly alive. But what of a virus? A virus is
a particle of organic material—mainly protein and nucleic acid—that utterly depends
upon a living host to reproduce. Some, including the authors of this book, do not con-
sider viruses living. But others argue quite convincingly otherwise. Even more perplex-
ing is the tiny nematode
, a microscopic worm that lives in seasonal ponds.
In the winter, the worm crawls and wriggles, clearly alive. But in summer, when the pond
dries up, the worm forms a dry coil that could turn into so much dust with a puff of air.