In algae, photosynthesis produces energy-rich carbon compounds by converting light energy into chemical energy. Which molecule is the primary initial carbon source that algae fix during photosynthesis?

• A. Carbon dioxide ($C_1{O}_2$)
• B. Glucose ($C_6{H}_{12}{O}_6$)
• C. Oxygen gas ($O_2$)
• D. Nitrogen gas ($N_2$)

Answer: (A)

Verified step by step guidance

1. Understand that photosynthesis in algae, like in plants, involves converting light energy into chemical energy stored in carbon compounds.
2. Identify the source of carbon atoms that algae use to build these energy-rich carbon compounds during photosynthesis.
3. Recall that the initial carbon source fixed in photosynthesis is a simple inorganic molecule taken from the environment.
4. Recognize that glucose is a product of photosynthesis, not the initial carbon source, and oxygen gas and nitrogen gas are not carbon sources.
5. Conclude that the primary initial carbon source fixed by algae during photosynthesis is carbon dioxide, represented chemically as \(\mathrm{CO_2}\).