The developmental process, independent of morphogenetic (shape) change, that is required for a glandular epithelial cell to attain its fully functional state. A glandular epithelial cell is a columnar/cuboidal epithelial cell is a cell found in a two dimensional sheet with a free surface exposed to the lumen of a gland [goid 2071] [evidence IEA]; The chemical reactions and pathways involving fatty acids, aliphatic monocarboxylic acids liberated from naturally occurring fats and oils by hydrolysis [goid 6631] [evidence IEA]; The secretion of milk by the mammary gland [goid 7595] [evidence ISS]; The chemical reactions and pathways, including anabolism and catabolism, by which living organisms transform chemical substances. Metabolic processes typically transform small molecules, but also include macromolecular processes such as DNA repair and replication, and protein synthesis and degradation [goid 8152] [evidence IEA]; The chemical reactions and pathways resulting in the formation of lipids, compounds soluble in an organic solvent but not, or sparingly, in an aqueous solvent [goid 8610] [evidence ISS]; The chemical reactions and pathways resulting in the formation of triacylglycerol, any triester of glycerol [goid 19432] [evidence ISS]; The process whose specific outcome is the progression of the mammary gland over time, from its formation to the mature structure. The mammary gland is a large compound sebaceous gland that in female mammals is modified to secrete milk [goid 30879] [evidence IEA]; Any process that modulates the frequency, rate or extent of growth of the body of an organism so that it reaches its usual body size [goid 40014] [evidence IEA]; The chemical reactions and pathways involving diacylglycerol, a glycerol molecule substituted on the 1 and 2 hydroxyl groups with long chain fatty acyl residues. DAG is a normal intermediate in the biosynthesis of phosphatidyl phospholipids and is released from them by phospholipase C activity. DAG from phosphatidyl inositol polyphosphates is important in signal transduction [goid 46339] [evidence IEA]