In the context of organic chemistry, which source of energy is utilized in the Calvin cycle?

• A. $ATP$
• B. $NADH$
• C. $GTP$
• D. $FAD{H}_2$

Answer: (A)

Verified step by step guidance

1. Understand the Calvin cycle: The Calvin cycle is a series of biochemical reactions that occur in the stroma of chloroplasts in photosynthetic organisms. It is part of the process of photosynthesis and is responsible for converting carbon dioxide and water into glucose, using energy derived from light reactions.
2. Identify the energy sources involved: The Calvin cycle primarily utilizes ATP and NADPH as energy sources. These molecules are generated during the light-dependent reactions of photosynthesis.
3. Differentiate between ATP and NADPH: ATP (adenosine triphosphate) provides the energy needed for the chemical reactions in the Calvin cycle, while NADPH (nicotinamide adenine dinucleotide phosphate) provides the reducing power necessary for the conversion of 3-phosphoglycerate into glyceraldehyde-3-phosphate.
4. Consider other energy carriers: GTP (guanosine triphosphate) and FADH2 (flavin adenine dinucleotide) are not directly involved in the Calvin cycle. GTP is more commonly associated with protein synthesis and signal transduction, while FADH2 is involved in cellular respiration.
5. Conclude the energy sources for the Calvin cycle: Based on the understanding of the Calvin cycle, ATP and NADPH are the correct energy sources utilized in this process, while GTP and FADH2 are not relevant to the Calvin cycle.