Which of the following is a major component of urine?

Urea is a major component of urine because it is a primary byproduct of protein metabolism in the body. When proteins are broken down, ammonia is produced, which is then converted into urea in the liver through the urea cycle. This conversion is crucial for detoxifying ammonia, as high levels of ammonia can be harmful. Urea is soluble and efficiently eliminated through the kidneys, which helps to regulate nitrogen levels in the body.

In healthy individuals, urea constitutes a significant portion of urine, accounting for about half of the total nitrogenous waste. Other components in urine, such as creatinine, glucose, and protein, can be present as well, but they do not comprise the same primary role in urine composition. For example, while creatinine is also a waste product from muscle metabolism, it is produced in smaller amounts compared to urea. Glucose is normally not present in urine in significant quantities unless there is an underlying condition such as diabetes, and protein should not be abundant in healthy urine.