Tissue culture is often a generic term that refers to both organ culture and cell culture and the terms are often used interchangeably. Cell cultures are derived from either primary tissue explants or cell suspensions. Primary cell cultures typically will have a finite life span in culture whereas continuous cell lines are, by definition, abnormal and are often transformed cell lines.Medium requirements: (often empirical)A. Bulk ions - Na, K, Ca, Mg, Cl, P, Bicarb or CO2 B. Trace elements - iron, zinc, selenium C. sugars - glucose is the most common D. amino acids - 13 essential E. vitamins - B, etc. F. choline, inositol G. serum - contains a large number of growth promoting activities such as buffering toxic nutrients by binding them, neutralizes trypsin and other proteases, has undefined effects on the interaction between cells and substrate, and contains peptide hormones or hormone-like growth factors that promote healthy growth. H. antibiotics - although not required for cell growth, antibiotics are often used to control the growth of bacterial and fungal contamination