Select all that apply: Select the true statement(s) . Endergonic reactions are always coupled t0 exergonic reactions. A reaction is considered to be biochemically freely reversible if it has a relatively small AG; The hydrolysis of ATP to ADP Is often used t0 drive endergonic reactions A reaction with a positive 4G never occurs_ ATP has higher Gibbs free energy than ADP
The Correct Answer and Explanation is:
Correct answers (select all that apply):
✅ Endergonic reactions are always coupled to exergonic reactions
✅ A reaction is considered to be biochemically freely reversible if it has a relatively small ΔG
✅ The hydrolysis of ATP to ADP is often used to drive endergonic reactions
✅ ATP has higher Gibbs free energy than ADP
❌ A reaction with a positive ΔG never occurs
Explanation
In biochemistry, understanding the role of energy in reactions is essential. Gibbs free energy (ΔG) tells us whether a reaction will proceed on its own. If ΔG is negative, the reaction is exergonic and releases energy. If ΔG is positive, the reaction is endergonic and needs energy input to proceed.
Endergonic reactions, which require energy, often occur only when they are coupled with exergonic reactions. A common way this happens in cells is by pairing an unfavorable (endergonic) reaction with ATP hydrolysis, which is highly exergonic (ΔG ≈ −30.5 kJ/mol under standard conditions). This coupling allows the overall process to become energetically favorable.
A reaction is biochemically reversible if the change in free energy (ΔG) is close to zero. This means that the forward and reverse reactions happen at similar rates, allowing the system to shift depending on the concentrations of reactants and products.
ATP (adenosine triphosphate) contains more stored energy than ADP (adenosine diphosphate) because it has more phosphate bonds. Breaking one of those high-energy bonds during ATP hydrolysis releases energy that can power cellular processes.
However, the statement that a reaction with a positive ΔG never occurs is false. Such reactions can and do happen in living cells, but only when they are coupled with exergonic reactions like ATP hydrolysis. The total combined ΔG for the coupled reactions must be negative for the overall process to proceed.
In summary, cells use the energy released from exergonic reactions, especially ATP hydrolysis, to drive essential endergonic processes, maintaining life and function.
