Page 96 - The Manga Guide to Biochemistry

4. ATP—The Common Currency of Energy

Plants and animals use cellular respiration to turn the sugar created by photosynthesis
into potential energy, mainly in the form of adenosine triphosphate (ATP). ATP is often
called the “common currency” of energy because it’s used by almost every living thing:
bacteria, plants—even complex organisms like Tom Cruise. However, individual molecules
of ATP are not exchanged between organisms, so how does it operate like currency?

As you can see below, ATP has three phosphate groups attached to adenosine. When
the outermost phosphate group is detached and becomes adenosine diphosphate (ADP)
and inorganic phosphate (Pi), 7.3 kcal (31 kJ) per mole of energy is released. If ATP is
hydrolyzed in a test tube, the surrounding water is warmed by this energy, but in an actual
cell that energy is used when an enzyme catalyzes a chemical reaction, a muscle moves,
or a neural signal is transmitted.

Adenosine
Adenine

3 phosphate
groups

O PPP

Ribose The energy that keeps

these two P s bonded

is stored here.

Adenosine triphosphate (ATP)

When the outermost phosphate P h 7.3 kcal (31 kJ) of
is detached to form adenosine y energy is used...
diphosphate (ADP) and inorganic d
r to create adenosine triphosphate
phosphate (Pi)... o (ATP) from adenosine diphosphate
l (ADP) and inorganic phosphate (Pi).
7.3 kcal (31 kJ) of y
energy is emitted. s
i
s

2 phosphate

+groups Pi

O PP

Adenosine Diphosphate (ADP) inorganic
phosphate

82 Chapter 2