Final answer:
The process most directly driven by light energy is Photosynthesis, a reaction in which green plants, algae, and some bacteria convert light into chemical energy. Cellular respiration is exergonic and releases energy, while photosynthesis is endergonic and requires energy input. Fermentation is anaerobic and begins with glycolysis, sharing pyruvate as a starting material with aerobic respiration.
Step-by-step explanation:
The process most directly driven by light energy is B. Photosynthesis. Photosynthesis is the process by which green plants, algae, and some bacteria convert light energy from the sun into chemical energy in the form of glucose, while also producing oxygen as a byproduct. This process can be illustrated by the chemical equation: 6CO2 + 6H2O + Light Energy → C6H12O6 + 6O2. Unlike photosynthesis, cellular respiration, glycolysis, and fermentation do not directly use light energy.
Focusing on the question related to whether each reaction is endergonic or exergonic:
- A. Cellular respiration is an exergonic process where glucose and oxygen react to form carbon dioxide and water, releasing energy that is stored as ATP.
- B. Photosynthesis is an endergonic process where light energy is captured and used to convert carbon dioxide and water into glucose and oxygen.
- C. Catabolic reactions, which break down complex molecules into simpler ones, are generally exergonic as they release stored energy.
- D. Anabolic reactions, which build complex molecules from simpler ones, are typically endergonic as they require an input of energy.
Lastly, fermentation is an anaerobic process that does not require oxygen and can produce ATP when oxygen is not available. It starts with glycolysis, which produces pyruvate, the same reactant shared by aerobic respiration and both types of fermentation (alcoholic fermentation and lactic acid fermentation).