ANATOMY

Detailed explanation-1: -Urea, ammonia and creatinine are metabolic waste products in protein metabolism. ‘Metabolic wastes’ also called ‘excrements’, are substances that are formed as by-products in the metabolic processes. These cannot be utilised by the organism and when accumulated in surplus can be toxic. Hence they must be excreted out.

Detailed explanation-2: -Urea, commonly referred to as blood urea nitrogen (BUN) when measured in the blood, is a product of protein metabolism. BUN is considered a non-protein nitrogenous (NPN) waste product. Amino acids derived from the breakdown of protein are deaminated to produce ammonia.

Detailed explanation-3: -Urea is the major byproduct of ammonia metabolism in vertebrate animals. Uric acid is the major byproduct of ammonia metabolism in birds, terrestrial arthropods, and reptiles.

Detailed explanation-4: -Metabolic wastes (carbon dioxide, water, oxygen, and nitrogenous compounds) diffuse through the cell membranes of these unicellular organisms into the outside environment.