Video Transcript
The diagram provided gives a basic outline of the relationship between ATP and
ADP. Which of the options correctly describes reactions X and Y? (A) Reaction X is hydrolysis and reaction Y is condensation. (B) Reaction X is condensation and reaction Y is hydrolysis. (C) Reaction X is reduction and reaction Y is oxidation. (D) Reaction X is oxidation and reaction Y is reduction.
We get energy from the food we eat, and much of this comes from the sugar molecule
glucose. This glucose has energy stored in its chemical bonds. And this energy can be extracted by a process called cellular respiration to convert
glucose into carbon dioxide and water. During this process, ATP is produced. ATP, or adenosine triphosphate, stores this energy in the form of high-energy
phosphate bonds. The three phosphate groups are linked to one another by high-energy bonds that can be
broken to release energy. When energy is needed, the covalent bond between the second and third phosphate
groups of ATP is broken and released for numerous biological processes in the
cell. This produces ADP, or adenosine diphosphate, which we can see on the bottom.
Notice how there’s now two phosphate groups. The inorganic phosphate group that was removed in this reaction is indicated as Pi on
the right. ADP can be converted back into ATP through the addition of a phosphate group, so ATP
is renewable. When ATP is broken down to ADP, this reaction is called a hydrolysis reaction because
a molecule of water is used to cleave the phosphate bond. And when ADP is converted back into ATP, this is called a condensation reaction
because this water molecule is released.
Therefore, the option that correctly describes reactions X and Y is given by answer
choice (A). Reaction X is hydrolysis and reaction Y is condensation.
