What is the process of taking smaller molecules and building them up called?

The process of taking smaller molecules and building them up into larger, more complex molecules is known as anabolism. This is a fundamental aspect of metabolism, which encompasses all biochemical reactions in the body. Anabolism specifically refers to the constructive part of metabolism where energy is utilized to synthesize molecules, such as proteins from amino acids, or glycogen from glucose. This building process is essential for growth, repair, and maintenance of cells and tissues.

In the context of the other terms provided, catabolism refers to the breakdown of larger molecules into smaller ones, releasing energy. Aerobic refers to processes that require oxygen, often relating to energy production through cellular respiration, while metabolism encompasses both anabolic and catabolic processes but does not specifically define the construction phase. Thus, anabolism is the accurate term to describe the building of smaller molecules into larger ones.