Video Transcript
The main function of ATP is to act
as a source of energy for cellular processes. The diagram shows a simple outline
of the structure of an ATP molecule. Which bond breaks to release the
energy stored in it?
Molecules of adenosine
triphosphate, which is often shortened to ATP, are used to store energy in the cells
of all living organisms. This question is asking us to work
out which bond in a molecule of ATP is used to store this energy. To work this out, let’s take a look
at the structure of an ATP molecule.
The name adenosine triphosphate
gives us a couple of clues about its structure. The prefix tri- means three,
telling us that there are three phosphate groups in one molecule of ATP. These phosphate groups are attached
to a ribose sugar. The prefix aden- tells us that this
ribose sugar is bound to a nitrogenous base called adenine.
When energy is needed immediately
in a cell, ATP is hydrolyzed. The prefix hydro- means water. And hydrolysis reactions involve
breaking down a molecule with the input of a water molecule. The hydrolysis of ATP breaks the
bond between the two outer phosphate groups. This releases the outermost
phosphate group along with the free energy that was stored in this bond to produce a
molecule of adenosine diphosphate, often shortened to ADP.
As we can deduce from the fact that
the prefix di- means two, adenosine diphosphate contains two phosphate groups as the
third phosphate group has been released through the hydrolysis of ATP.
Now we have enough information to
answer our question. The high-energy bond that is broken
to release the energy stored in it is found between the two outermost phosphate
groups in an ATP molecule, which is labeled in this diagram with the number one.
