Chemistry 30 Diploma Practice Exam

Photosynthesis is the process that uses light energy to build sugars from carbon dioxide and water, with oxygen released as a byproduct. In the chloroplasts of plants and some microorganisms, light is captured by pigments like chlorophyll. The light-dependent reactions use that energy to split water, producing oxygen gas and energizing carriers (ATP and NADPH). Those energy carriers then power the Calvin cycle, which fixes carbon dioxide into glucose. So the inputs are CO2, water, and light, and the main outputs are sugar and O2.

Cellular respiration, by contrast, breaks down sugars using oxygen to release energy and CO2 and water, not form sugars from CO2 and water. Bond energy and heat of formation describe general thermodynamic concepts, not a specific metabolic process.