During heavy physical exercise, a sprinter's leg muscles undergo anaerobic respiration. Select the option that correctly identifies the substance produced in the muscle cells, the location of this pathway inside the cell, and the symptom it triggers.

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A Ethanol; Mitochondria; High fever
B Carbon dioxide; Nucleus; Muscle spasms
C Lactic acid; Cytoplasm; Muscle cramps
D Pyruvate; Chloroplast; Joint swelling

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Answer: C. Lactic acid; Cytoplasm; Muscle cramps

Answer: C) Lactic acid; Cytoplasm; Muscle cramps
Explanation: When oxygen demand outpaces supply during intense exercise, pyruvate (broken down from glucose in the cytoplasm) is converted into lactic acid instead of entering the mitochondria. This anaerobic pathway takes place entirely in the cytoplasm and releases very little energy (2 ATP). The sudden accumulation of lactic acid causes painful muscle cramps.

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During heavy physical exercise, a sprinter's leg muscles undergo anaerobic respiration. Select the option that correctly identifies the substance produced in the muscle cells, the location of this pathway inside the cell, and the symptom it triggers.

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