Which of the following is the primary purpose of cellular respiration in eukaryotic cells?

• A. To break down ATP into ADP and phosphate
• B. To synthesize glucose from sunlight
• C. To produce oxygen from carbon dioxide
• D. To convert glucose into usable ATP energy

Answer: (D)

Verified step by step guidance

1. Understand the concept of cellular respiration: Cellular respiration is a metabolic process that occurs in eukaryotic cells to convert biochemical energy from nutrients, primarily glucose, into adenosine triphosphate (ATP), which is the usable form of energy for cellular activities.
2. Identify the key molecules involved: Glucose is the primary fuel molecule, and oxygen is required as the final electron acceptor in the process. ATP is the energy currency produced, while carbon dioxide and water are byproducts.
3. Break down the stages of cellular respiration: Cellular respiration consists of three main stages: glycolysis (occurs in the cytoplasm), the citric acid cycle (occurs in the mitochondria), and oxidative phosphorylation (occurs in the inner mitochondrial membrane). Each stage contributes to ATP production.
4. Clarify the role of ATP: ATP is a molecule that stores and transfers energy within cells. The energy released during cellular respiration is used to synthesize ATP from ADP and inorganic phosphate (${\mathrm{ADP}}_{}+P_{}\to {\mathrm{ATP}}_{}).$
5. Eliminate incorrect options: Cellular respiration does not break down ATP into ADP and phosphate (this happens during energy use, not production), does not synthesize glucose from sunlight (this is photosynthesis), and does not produce oxygen from carbon dioxide (oxygen is consumed, not produced). The correct purpose is to convert glucose into usable ATP energy.