Question

which of the following statements best describes the critical role that atp plays in cellular metabolism?
the covalent bond on the terminal phosphate of atp is particularly strong, so it releases extra energy when hydrolyzed.
it is one of the four building nucleotides required for dna synthesis.
atp hydrolysis provides the energy used to power exergonic reactions in the cell.
atp serves as an energy shuttle in the cell, coupling exergonic and endergonic reactions.

Explanation:

• First option: The bonds in ATP are not "extra - strong." They are high - energy bonds, but the term "extra strong" is incorrect. When ATP is hydrolyzed, the energy is released due to the instability of the phosphate bonds, not because they are "extra strong."
• Second option: The nucleotide for DNA synthesis is dATP (deoxyadenosine triphosphate), not ATP. ATP has a ribose sugar, while DNA requires a deoxyribose sugar.
• Third option: Exergonic reactions release energy. ATP hydrolysis provides energy for endergonic (energy - requiring) reactions, not exergonic reactions.
• Fourth option: ATP acts as an energy shuttle. Exergonic reactions (which release energy) are coupled with the phosphorylation of ADP to ATP. Then, ATP hydrolysis (an exergonic process for ATP) is coupled with endergonic reactions (which require energy) in the cell.

Answer:

ATP serves as an energy shuttle in the cell, coupling exergonic and endergonic reactions.