Glutamine is also known as a cell volumizer. Clinical studies show that glutamine infusion helps maintain muscle mass in critically ill patients. If the amount of glutamine in your diet is insufficent then your body will borrow needed glutamine from skeletal muscle. As you can see, Glutamine is crucial to the human body, especially in the skeletal muscles and immune system. It is an excitatory amino acid due to its role as a neurotransmitter.
Glutamic acid is a very polar molecule usually found outside of proteins and enzymes.
Glutamic acid is easily converted from glutamine but it was not isolated from protein until 1932. Muscle and Fitness, August 1999, p. 100.