Video Transcript
Which of the following best
describes the structure of an ATP molecule? (A) An ATP molecule is composed of
a ribose sugar, an adenine nitrogenous base, and three phosphate groups. (B) An ATP molecule is composed of
a deoxyribose sugar, an adenine nitrogenous base, and two phosphate groups. (C) An ATP molecule is composed of
a hexose sugar, three adenine nitrogenous bases, and a phosphate group. Or (D) an ATP molecule is composed
of a glucose molecule, three adenine nitrogenous bases, and a phosphate group.
In order to answer this question,
we’re going to need to see a diagram of ATP. So let’s remove our answer options
for now. Adenosine triphosphate, which is
the full name for the molecule ATP, is a nucleotide that stores chemical energy in
living organisms. All nucleotides are made up of the
same basic structure: a nitrogenous base; a pentose sugar, which means that it
contains five carbons; and one or more phosphate groups.
Given the full name of ATP, we can
work out a few things about its structure. The prefix aden- in adenosine
triphosphate tells us that the nitrogenous base it contains is adenine, while the
tri- in triphosphate tells us that there are three phosphate groups in an ATP
molecule. But what about the pentose
sugar? As we now know, there are five
carbons in a pentose sugar, while a hexose sugar like glucose would have six
carbons, as the prefix hex- means six, while the prefix pent- means five.
While we can’t necessarily deduce
this from its name, the pentose sugar in adenosine triphosphate is ribose. So we’ve deduced that the structure
of an ATP molecule includes a ribose sugar, a nitrogenous adenine base, and three
phosphate groups. Let’s bring back our answer
options. So we’ve worked out that an ATP
molecule is composed of a ribose sugar, an adenine nitrogenous base, and three
phosphate groups.
