Final answer:
The statement that nitrogen retention is key to anabolism is true, as positive nitrogen balance indicates the availability of nitrogen for tissue synthesis essential during growth and recovery.
Step-by-step explanation:
It is true that nitrogen retention is key to anabolism. Anabolism refers to the set of metabolic pathways that construct molecules from smaller units. These metabolic reactions typically require energy. In the context of nitrogen metabolism, anabolism involves the incorporation of nitrogen into organic compounds, such as the synthesis of amino acids, which are the building blocks of proteins.
When an organism is in a positive nitrogen balance, it means that the intake of nitrogen, usually through the consumption of proteins, exceeds the loss of nitrogen through waste products. This surplus of nitrogen represents the organism's ability to synthesize new tissue, which is essential, especially during periods of growth, recovery from injury, and during pregnancy.