Final answer:
Nitrogen is vital for life because it is a necessary component of amino acids and proteins. Nitrogen for biochemical synthesis originates from dietary proteins or nitrogen fixation in plants. Humans must obtain essential amino acids through their diet, while plants get nitrogen from the soil.
Step-by-step explanation:
Nitrogen is essential because it is a key component of amino acids and proteins, which are fundamental to the structure and function of all living cells. Proteins perform a variety of functions in the body, including catalyzing metabolic reactions, DNA replication, responding to stimuli, providing structure to cells and tissues, and transporting molecules from one location to another. Nitrogen needed for amino acids and proteins primarily comes from the food we eat. For instance, dietary proteins are broken down into amino acids, which are then used by cells to construct new proteins. Not all amino acids can be synthesized by the human body, and these essential amino acids must be obtained from our diet. Moreover, plants acquire nitrogen through nitrogen fixation, which converts atmospheric nitrogen into compounds like nitrate ions (NO3−) and ammonia (NH3), which the plants can then use. The nitrogen cycle describes this process of fixing atmospheric nitrogen into a usable form and its re-release into the atmosphere through a series of biological transformations.