The question here is whether the biochemical processes observable on Earth would be replicated on another planet. Take photosynthesis as an example. This is the means by which plants utilise sunlight in the production of adenosine triphosphate (ATP) and glucose as sources of energy. During this process oxygen is given off and carbon dioxide is absorbed, hence the value of photosynthesis for environments on our planet. The actual process is highly complex and involves electrons going through intricate chemical reactions leading at the end to glucose formation. There is also a kind of reverse process, which involves the release of energy through the oxidation of a chemical derived from carbohydrates, fats and proteins. This is known as the citric acid cycle, an essential metabolic pathway used by aerobic organisms.