The diagram above is an illustration of the urinary tubule in a mammal. Which of the following substances is greater in concentration in the part labelled I...

Answer Details

The substance that is greater in concentration in the part labeled IV when compared to that part labeled I is Urea. The urinary tubule is a part of the renal system and is responsible for filtering waste products from the blood and reabsorbing important substances back into the bloodstream. In the diagram, the part labeled I represents the beginning of the urinary tubule, where the blood is filtered to remove waste products. The part labeled IV represents the end of the tubule, where the final concentration of waste products is determined. Urea is a waste product produced by the liver and is present in high concentrations in the blood. As the blood passes through the urinary tubule, some of the urea is reabsorbed back into the bloodstream, but most of it continues to be filtered and concentrated in the part labeled IV. The concentration of urea in the part labeled IV is therefore greater than that in the part labeled I. Lipids, glucose, and uric acid are not primarily waste products of the renal system, but they can be filtered and reabsorbed in small amounts along with urea and other waste products.