Question

Muscle growth due to protein synthesis is an example of what kind of reaction

Answer 1

Muscle growth due to protein synthesis is an example of anabolic reaction. Anabolic reactions are those metabolic reactions that involve growth. 

Answer 2

Biological reactions can be classified as being of two main types: anabolic and catabolic. Catabolic reactions involve the break down of a larger molecule to release energy and smaller molecules; meanwhile, anabolic reactions are the opposite such that they involve the combination of molecules while consuming energy to form larger molecules. 
Muscle growth is anabolic because polypeptides are formed using amino acids and energy.