In the context of cellular respiration, where does the glucose that is released into the blood ultimately end up after being taken up by body cells?

• A. It is broken down in the mitochondria to produce ATP.
• B. It is excreted unchanged in the urine.
• C. It is stored in the nucleus as DNA.
• D. It is converted directly into proteins.

Answer: (A)

Verified step by step guidance

1. Understand the process of cellular respiration: Cellular respiration is the metabolic pathway where glucose is broken down to produce ATP, the energy currency of the cell. This occurs primarily in the mitochondria.
2. Eliminate incorrect options: Glucose is not excreted unchanged in the urine because it is typically reabsorbed by the kidneys unless there is a medical condition like diabetes. Glucose is not stored in the nucleus as DNA because DNA is composed of nucleotides, not glucose. Glucose is not directly converted into proteins because proteins are synthesized from amino acids, not glucose.
3. Focus on the correct pathway: Glucose is taken up by body cells and enters the cytoplasm, where it undergoes glycolysis to produce pyruvate. Pyruvate is then transported into the mitochondria for further breakdown in the citric acid cycle and oxidative phosphorylation.
4. Explain ATP production: In the mitochondria, glucose is fully oxidized to produce ATP through processes like the citric acid cycle and the electron transport chain. ATP is then used by the cell for various energy-requiring activities.
5. Conclude the correct answer: Based on the steps above, the glucose taken up by body cells is broken down in the mitochondria to produce ATP, which is the correct answer.