Final answer:
In the synthesis of glutamine from glutamic acid, phosphate is displaced by ammonia (NH3) in a key reaction catalyzed by glutamine synthetase. Option D is correct.
Step-by-step explanation:
The condensation step involves the conversion of glutamic acid to glutamine through an enzyme catalyzed reaction with glutamine synthetase. During this process, a phosphate is displaced by an ammonia (NH3) group.
This reaction is essential for removing excess ammonia from the body, making glutamine an important nonessential amino acid for ammonia detoxification. Glutamine is then available for various biochemical processes including the synthesis of other amino acids and the urea cycle.