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

I. Basic Nutritional Components

1. Amino Acids
   • Raw Materials for Protein Synthesis: Cells need a variety of amino acids for synthesizing their own proteins. Among them, essential amino acids, which cannot be synthesized by cells themselves, must be provided by the culture medium. For example, L – glutamine is a crucial amino acid that is easily depleted during cell growth and is important for maintaining the normal metabolism and growth of cells.
   • Regulating Osmotic Pressure: Amino acids in the solution can affect the osmotic pressure of the culture medium, keeping it within a range suitable for cell survival and growth.
2. Carbohydrates
   • Energy Supply: Glucose is the most common carbohydrate in cell culture medium and is the main source of energy for cells. Cells break down glucose through glycolysis and other metabolic pathways to produce ATP (adenosine triphosphate), which provides energy for various cellular activities.
   • Metabolic Intermediates: In the culture of some special cells, other sugars such as galactose or fructose can also be used as energy sources or participate in specific intracellular metabolic processes according to the specific metabolic requirements of the cells.
3. Vitamins
   • Cofactors for Enzymatic Reactions: B – group vitamins (such as B1, B2, B6, etc.) play important roles in cellular metabolism. They act as coenzymes or cofactors for many enzymatic reactions, participating in intracellular energy metabolism, substance synthesis and decomposition, etc. For example, a lack of vitamins will lead to a decrease in the activity of related enzymes in cells, thereby affecting cell growth and function.
   • Antioxidant Effects: Some vitamins (such as vitamin C) have antioxidant functions and can protect cells from oxidative stress damage, maintaining the stability of the intracellular environment, which is especially important for some cell types that are vulnerable to oxidative damage.
4. Inorganic Salts
   • Maintaining Cell Membrane Potential: Sodium and potassium ions are crucial for maintaining the resting potential of the cell membrane. For example, the sodium – potassium pump on the cell membrane continuously pumps sodium ions out of the cell and potassium ions into the cell by consuming ATP, thereby forming and maintaining the cell membrane potential and ensuring the normal excitability and substance transport functions of cells.
   • Participating in Cell Signaling: Calcium ions are important second messengers in cells and participate in numerous cell signaling processes, such as muscle contraction, neurotransmitter release, cell proliferation and differentiation. When extracellular signaling molecules bind to receptors on the cell membrane, they cause changes in the intracellular calcium ion concentration, which then trigger a series of cellular responses.
   • Maintaining Osmotic Pressure and Enzyme Activity: Magnesium ions are co – factors for many enzymes and participate in various intracellular enzymatic reactions. For example, the activation of ATPase requires magnesium ions. At the same time, various inorganic salt ions jointly maintain the osmotic pressure of the culture medium, balancing it with the intracellular osmotic pressure and preventing cells from being damaged due to excessive water absorption or loss.
   • Participating in Nucleic Acid and Energy Metabolism: Phosphate ions are important components of ATP and participate in cellular energy metabolism. They are also essential raw materials for nucleic acid synthesis and are of great significance for cell growth and division.

II. Growth Factors and Hormones

1. Growth Factors
   • Stimulating Cell Proliferation: Epidermal growth factor (EGF) can promote cell proliferation, especially of epithelial cells. After binding to cell – surface receptors, it activates intracellular signaling pathways, prompting cells to enter the cell cycle for division.
   • Promoting Cell Differentiation: Fibroblast growth factor (FGF) is crucial for the growth and differentiation of fibroblasts and many other cell types. It can induce cells to differentiate in specific directions and plays important roles in embryonic development, tissue repair and regeneration.
   • Participating in Physiological Function Regulation: Platelet – derived growth factor (PDGF) participates in the wound – healing process. It can stimulate the proliferation and migration of fibroblasts, smooth muscle cells, etc., and promote the synthesis of extracellular matrix, thereby accelerating wound repair.
2. Hormones
   • Regulating Cell Metabolism: Insulin is often added to cell culture medium, which can regulate cells’ uptake and utilization of glucose and maintain the intracellular energy balance. For some cells that rely on glucose as the main energy source, the presence of insulin helps ensure the normal growth and metabolism of cells.