culture serum The serum used in cell culture medium. Cultured cells require serum or growth factors for growth by cell division. In the laboratory, each cell type is grown in a medium supplemented with a variable concentration of serum (up to 20%) which is optimized for its growth. Specialized sera include dextran charcoal treated serum, which lacks certain hormones, growth factors, etc, dialyzed serum, which lacks low molecular weight molecules (below 10,000 MW), such as glucose, amino acids, low molecular weight hormones, cytokines, etc. Most commonly, fetal bovine serum is used in cell culture, but other sera such as horse serum are also used. material entity