In mammalian cell culture, what does a culture medium primarily provide to living cells to support their survival and growth?

• A. Essential nutrients, appropriate ions/osmolarity, buffering to maintain pH, and (often) growth factors
• B. Direct ATP production by supplying mitochondria with ready-made ATP to bypass metabolism
• C. Genetic instructions (DNA) needed for transcription and translation of all cellular proteins
• D. A solid extracellular matrix that permanently anchors cells and replaces the need for cell adhesion molecules

Answer: (A)