Is Photosynthesis Endergonic or Exergonic?

Photosynthesis is classified as an endergonic process. This means that it uses energy to obtain energy, and by doing so, organic compounds are anaerobically produced. In order to carry out photosynthesis, plants must first obtain sunlight, water, carbon dioxide and chlorophyll through an endergonic process.

Endergonic Process

"Endergonic" entails the absorbtion of energy through work. Because plants take in solar energy, water, carbon dioxide and chlorophyll to begin the energy process, photosynthesis is considered endergonic. In photosynthesis, energy-carrying molecular bonds are formed. These bonds obtain energy from the sun and transfer it throughout the plant.

Exergonic Process

An exergonic process works to release energy. When it does so, its surroundings receive that energy. An example of this is a ball rolling down a hill; the ball will continue rolling according to the Second Law of Thermodynamics (energy will increase itself overtime), yielding useful energy that will proceed if left to itself.


Energy itself is the capacity to do work. The main component of photosynthesis is sunlight, which is carried through the plant by electrons. As these electrons are powered by chemical energy, they reposition themselves to form CO2. To counteract entropy (energy that is not available for work) during photosynthesis, this energy from sunlight is necessary.

Energy Sources of Photosynthesis

To adequately carry out photosynthesis, sunlight is not the only necessary energy input. Water, carbon dioxide and chlorophyll are also important properties throughout the process. By using all four of these natural energizers, food--in the form of sugars and oxygen--is produced.

Energy Carrier Molecules

The two most common electron carriers (the intermediaries which transform energy through photosynthesis into carbon dioxide) are nicotinamide adenine dinucleotide (NAD+) and flavin adenine dinucleotide (FAD). They are vital to the endergonic process in that they are the "messengers" carrying absorbed sources of energy throughout the plant.