An endergonic reaction has a positive ΔG’ and requires the input of energy to proceed as written. Question 50 options: True False
The Correct Answer and Explanation is:
Correct Answer: True
An endergonic reaction is characterized by a positive ΔG’, which means that the Gibbs free energy of the products is greater than that of the reactants. This increase in free energy indicates that the reaction is non-spontaneous under standard conditions and requires an input of energy in order to proceed.
The symbol ΔG’ represents the change in Gibbs free energy under standard biochemical conditions, such as a temperature of 25°C, a pressure of 1 atmosphere, and concentrations of 1 M for all reactants and products, with pH = 7 for biological systems. A positive ΔG’ means that the system must absorb energy from its surroundings to move forward.
In biological systems, many necessary processes are endergonic, including the synthesis of complex molecules like proteins, nucleic acids, and polysaccharides. These processes cannot happen on their own because they move against the natural direction of increasing entropy. To overcome this energy barrier, cells couple endergonic reactions with exergonic reactions, such as the hydrolysis of adenosine triphosphate (ATP), which releases energy (negative ΔG’).
For example, in the synthesis of glucose-6-phosphate from glucose and phosphate, the reaction is endergonic. However, when it is coupled with the hydrolysis of ATP, the overall reaction becomes exergonic and can occur spontaneously. This is a key strategy that cells use to drive non-spontaneous biochemical processes.
In summary, the statement is true. Endergonic reactions have a positive ΔG’ and require an input of energy because the products have more free energy than the reactants. This energy requirement distinguishes them from exergonic reactions, which release energy and occur spontaneously.
