MCAS Biology Practice Test 2026 – Complete Exam Preparation

Photosynthesis is the correct choice because it is the fundamental process that allows plants to convert light energy from the sun into chemical energy stored in glucose. This process primarily occurs in the chloroplasts of plant cells, where chlorophyll captures sunlight. During photosynthesis, carbon dioxide from the air and water from the soil are used, along with sunlight, to produce glucose and oxygen as byproducts.

In more detail, the overall equation for photosynthesis can be summarized as:

6CO2 + 6H2O + light energy → C6H12O6 + 6O2

This highlights how light energy is utilized to transform inorganic substances (carbon dioxide and water) into an organic compound (glucose), which serves as energy for the plant and other organisms that consume it.

The other processes listed do not play a role in converting sunlight into chemical energy. Cellular respiration, for example, is a process that breaks down glucose into energy, whereas transpiration refers to the movement of water through a plant and its evaporation, and fermentation is an anaerobic process that breaks down glucose without oxygen.