Trypsin is the principal pancreatic serine endopeptidase secreted into the alkaline/neutral lumen of the fish intestine. It hydrolyzes peptide bonds on the carboxyl side of basic amino acids (lysine and arginine). Pepsin operates exclusively under acidic conditions in the stomach, while amylase and lipase digest carbohydrates and lipids, respectively.

Specific Dynamic Action (SDA), also called the Heat Increment of Feeding (HIF) or Diet-Induced Thermogenesis, refers to the mandatory postprandial increase in metabolic rate and energy expenditure above basal levels associated with the mechanical ingestion, digestion, absorption, and biochemical assimilation/deamination of dietary nutrients (especially proteins).

In mitochondrial $\beta$-oxidation of saturated even-numbered fatty acyl-CoA chains, each repetitive four-step cyclic cleavage sequentially releases a 2-carbon fragment in the form of Acetyl-CoA ($CH_3-CO-SCoA$), which directly enters the Krebs citric acid cycle for ATP generation.