Penn State Master Gardener Practice Exam

Photosynthesis uses light energy to drive the synthesis of sugars from carbon dioxide and water. In the light-dependent reactions, chlorophyll captures light and converts it into chemical energy in the form of ATP and NADPH. The subsequent Calvin cycle uses that energy to fix carbon dioxide into three-carbon sugars, which are eventually assembled into glucose and stored as starch in chloroplasts and other plastids. This stored energy in sugars and starch is what powers growth and metabolism when light isn’t available. Other plant processes do not fit this role. Respiration consumes sugars and oxygen to release energy for cellular work, producing carbon dioxide and water. Transpiration involves water loss through stomata and is about movement and cooling, not sugar synthesis. Propagation is about reproduction, not energy capture from light for carbohydrate production.