Which substance is produced from the metabolism of muscle?

Creatinine is the correct answer because it is a byproduct of muscle metabolism, specifically derived from the breakdown of creatine, which is an important compound involved in energy production in muscle tissue. As muscles utilize creatine for the generation of ATP (adenosine triphosphate), creatinine is formed and released into the bloodstream. The kidneys filter creatinine out of the blood, and it is excreted in urine, making it a reliable marker for assessing kidney function and muscle mass.

In contrast, uric acid is primarily a product of purine metabolism, which is not directly linked to muscle metabolism. Calcium, while essential for muscle contraction and numerous cellular processes, is not a metabolic byproduct but rather a vital mineral involved in various physiological functions. Ammonium is produced during protein metabolism, particularly through the deamination of amino acids, which is also unrelated to direct muscle metabolism. Thus, creatinine stands out as the key substance produced specifically from muscle activity.