Energy from the sun fuels a biological process called ______.

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

Answer: (A)

Sunlight powers photosynthesis, the process by which chlorophyll-containing cells capture light energy to build sugars from carbon dioxide and water. In the light-dependent reactions, light energy drives the creation of ATP and NADPH, which the plant then uses in the Calvin cycle to synthesize glucose. Oxygen is released as a byproduct. This conversion of light energy into chemical energy stored in sugars is why energy from the sun is essential for nearly all life on Earth.

The other processes don’t fit this role. Respiration uses the already-made sugars to release energy; fermentation provides a way to generate energy without oxygen; and transpiration is simply the loss of water from a plant and does not involve converting light into chemical energy.