Which process do green plants use to convert light energy and carbon dioxide into glucose and oxygen?

• A. Respiration
• B. Fermentation
• C. Photosynthesis
• D. Transpiration

Answer: (C)

Photosynthesis is the process by which green plants convert light energy and carbon dioxide into glucose and oxygen. In the chloroplasts, light energy drives chemical reactions that combine carbon dioxide from the air with water from the soil to form glucose, a stored form of chemical energy, while releasing oxygen as a byproduct. This is why plants can produce their own food using sunlight.

Respiration, by contrast, uses the glucose produced by photosynthesis to release energy for the cell, producing carbon dioxide and water as byproducts and not creating new sugar. Fermentation can occur without oxygen and yields energy in the absence of air but does not use light to build glucose. Transpiration is the loss of water vapor from plant surfaces and is not a process that makes glucose or oxygen.

So the described process—using light energy and carbon dioxide to make glucose and oxygen—is photosynthesis.