Final answer:
Endergonic reactions absorb energy, and exergonic reactions release energy. Cellular respiration is exergonic, photosynthesis is endergonic, catabolic reactions are exergonic, and anabolic reactions are endergonic. Both require activation energy, depicted as an energy barrier on a reaction coordinate diagram.
Step-by-step explanation:
Identifying whether a reaction is endergonic or exergonic can be determined based on the change in Gibbs free energy of the reaction. Reactions with a negative Gibbs free energy (ΔG) are considered exergonic, meaning they release energy to the surroundings. On the other hand, reactions with a positive ΔG are classified as endergonic, meaning they absorb energy from the surroundings.
- A. Cellular respiration is an example of an exergonic reaction as it releases energy.
- B. Photosynthesis is an endergonic process because it requires an input of energy to proceed.
- C. Catabolic reactions are typically exergonic because they break down molecules and release energy.
- D. Anabolic reactions are typically endergonic because they build complex molecules from simpler ones and consume energy.
The activation energy is the initial energy input required for a reaction to occur, and it is represented on a reaction coordinate diagram as the energy barrier between reactants and the transition state. Both endergonic and exergonic reactions require activation energy to overcome this barrier.
On a reaction coordinate diagram, reactants are plotted based on their initial energy state, and products are plotted based on their final energy state. In an exergonic reaction, the products are at a lower energy state compared to reactants, while in an endergonic reaction, the products are at a higher energy state than the reactants.