Final answer:
Atmospheric nitrogen is inert and cannot be used directly by plants or animals. However, specialized microorganisms like bacteria can fix this nitrogen into a usable form through nitrogen fixation. This transformed nitrogen then supports various ecosystem dynamics, being a critical element in amino acids and proteins across the food chain.
Step-by-step explanation:
The role of atmospheric nitrogen in biochemical processes is not a direct one. Instead, atmospheric nitrogen, which makes up about 78 percent of the Earth's atmosphere, must first be converted through a process called nitrogen fixation. This conversion is carried out by specialized microorganisms, primarily bacteria, that convert the inert nitrogen gas (N₂) into ammonia (NH₃) which can then be used by plants. This process forms the backbone of the nitrogen cycle, a series of biochemical transformations that make nitrogen available for biological use, contributing significantly to the structure and function of ecosystems.
In symbiotic relationships, for example, nitrogen-fixing bacteria form nodules on the roots of legume plants, enabling these plants to use the fixed nitrogen to synthesize amino acids and form proteins. Through consumption, this nitrogen enters the food chain and becomes available to a wider range of organisms. Eventually, the nitrogen is converted back into its gaseous form and returned to the atmosphere by a process called denitrification, thus completing the cycle.