The functions of various components in cell culture medium are as follows:

I. Other Additives

1. Serum
   • Providing Rich Nutrition: Fetal bovine serum (FBS) is a commonly used additive in cell culture. It contains a large number of proteins, growth factors, hormones and other bioactive substances, which can provide comprehensive and rich nutritional support for cell growth. These substances can promote cell adhesion, proliferation, differentiation and other processes.
   • Protecting Cells: Some components in serum can protect cells. For example, some proteins can bind and neutralize toxic substances in the culture medium, reducing damage to cells.
   • Disadvantages: However, the use of serum has some drawbacks. For example, there are differences in composition and quality among different batches of serum, which may affect the stability of cell culture results. In addition, serum may introduce potential contaminants, such as viruses and mycoplasmas, posing a contamination risk to cell culture.
2. Antibiotics
   • Preventing Bacterial Contamination: Antibiotics such as penicillin and streptomycin are usually added to cell culture medium to prevent bacterial contamination. Bacterial contamination is a common problem in cell culture. Once bacteria contaminate, they will multiply rapidly, compete with cells for nutrients and produce toxins, leading to cell death. The addition of antibiotics can reduce this risk to some extent.
   • Potential Problems: However, over – use of antibiotics may lead to the emergence of antibiotic – resistant bacteria and may mask some mild contamination situations, making it difficult for experimenters to detect potential problems.
3. Buffering Systems
   • Maintaining pH Stability: A good buffering system is essential for maintaining the pH of cell culture medium. Commonly used buffering systems include bicarbonate – CO2 and HEPES. Cells will produce acidic or alkaline metabolites during growth, and these buffer substances can neutralize the pH changes caused by these metabolites, keeping the pH of the culture medium within a range suitable for cell growth (usually 7.2 – 7.4). If the pH of the culture medium is beyond the appropriate range, it will affect the enzymatic activity, membrane permeability and other physiological characteristics of cells, thereby affecting cell growth and survival.