Video Transcript
What is the primary difference
between an ATP molecule and an ADP molecule? (A) A molecule of ATP contains a
ribose sugar, but a molecule of ADP contains deoxyribose. (B) A molecule of ATP has three
phosphate groups, but a molecule of ADP only has two. (C) A molecule of ATP contains the
nitrogenous base adenine, but a molecule of ADP contains the nitrogenous base
uracil. Or (D) there is no difference
between the structure of an ATP molecule and that of an ADP molecule.
ATP is the molecule that stores
energy in the cells of living organisms. When the cell requires immediate
energy, ATP molecules undergo hydrolysis reactions, which involves splitting the
molecules using water. The hydrolysis of ATP produces a
molecule of ADP and a phosphate molecule. It also releases free energy that
the cell can use. So, what is the chemical difference
between ATP and ADP?
ATP is short for adenosine
triphosphate. The prefix tri- indicates that a
molecule of ATP has three phosphate groups. The phosphate groups are bound to a
ribose sugar, which is in turn attached to a nitrogenous base called adenine. ADP, on the other hand, is short
for adenosine diphosphate. And the prefix di- means two,
indicating that a molecule of ADP has two phosphate groups.
Otherwise, the structure of an ATP
molecule is identical to a molecule of ADP. When ATP is hydrolyzed, the
addition of water catalyzes the separation of the outermost phosphate group from the
molecule.
Now, we have enough information to
answer this question correctly. The primary difference between an
ATP molecule and an ADP molecule is (B). A molecule of ATP has three
phosphate groups, but a molecule of ADP only has two.
