"Glutamine is an amino acid that makes up 50 to 60% of the total amino acids found in muscles. It is used to off set the negative effects of ammonia that is produced with hard workouts. When the body is stressed, glutamine leaves the muscles and is sent into the blood to support the immune system. It is the "immunity amino acid" - it supports the immune system. Immune support is more important than muscle growth for survival. The immune system must be supported first before muscle growth can occur. Low muscle glutamine levels means no muscle growth. Glutamine, like all amino acids, produce ammonia BUT it decreases more ammonia than it produces. The net effect is LESS ammonia."
"Creatine Monohydrate is a supplement that can increase creatine phosphate levels in the body. Increasing creatine phosphate levels allow more ATP to be made. All muscle contraction and muscle growth depends on adequate ATP levels. Insufficient levels of creatine phosphate leads to exhaustion and incomplete muscle recovery."
"Creatine Phosphate is a high energy compound that acts as a reservoir or back up for the energy producing compound, ATP or adenosine triphophate.
All energy production, muscle building, and muscle contraction relies upon ATP. ATP is made from the foods we eat. Only a small amount of ATP is stored in the cells. Creatine Phosphate is also stored in muscle. It is derived from foods especially red meat. When ATP is used as fuel, the body reduces the ATP to ADP. Creatine phosphate combines with ADP to make new ATP so more energy can be produced."
Taken from Chris Aceto's Understanding Bodybuilding Nutrition & Training