#laboratory media

Animal Tissue Culture 1

The major role of sodium bicarbonate in culture media is:

Sodium bicarbonate central role in mammalian physiology reproducing blood acid base homeostasis via carbonic acid bicarbonate buffer pair handling volatile acid carbon dioxide produced by cellular respiration ten thousand times more than fixed acids lactate. Enzyme carbonic anhydrase family zinc metalloenzymes CA I II IX highly efficient catalyzing hydration CO2 plus H2O ↔ H2CO3 ↔ HCO3- plus H+ turnover near diffusion limit 10^6 per second enabling rapid equilibration. In culture when glucose metabolized via glycolysis to lactate plus proton, proton combines with bicarbonate producing carbonic

Ref: Freshney bicarbonate buffering carbonic acid pH Henderson-Hasselbalch; Lodish MBoC carbamoyl phosphate pyrimidine bicarbonate carbon source.

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Animal Tissue Culture 1

The osmolarity of basal media generally ranges between:

Plasma osmolarity tightly regulated in mammals at approximately two hundred eighty five to two hundred ninety five milliosmoles per liter by neuroendocrine circuit involving hypothalamic osmoreceptors magnocellular neurons in supraoptic nucleus sensing shrinkage, releasing antidiuretic hormone vasopressin from posterior pituitary promoting aquaporin-2 insertion in collecting duct increasing water reabsorption, ensuring stable cell volume via aquaporin water channels bidirectional passive transport. Basal culture media attempt to mimic plasma tonicity to avoid osmotic stress altering cytoskelet

Ref: Waymouth 1970 osmolarity basal media 260-320 mOsm plasma tonicity; Freshney aquaporin VRAC NKCC volume regulation isotonic.

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Animal Tissue Culture 1

DMEM generally requires CO₂ concentration of:

Nutrient dense formulation of Dulbecco's Modified Eagle's Medium doubles concentration of essential and nonessential amino acids compared to MEM original Eagle minimal essential medium, quadruples vitamin concentrations niacinamide B3, pyridoxal B6, riboflavin B2 to support nucleotide and cofactor synthesis in rapidly proliferating transformed cells, increases glucose from 1 to 4.5 grams per liter to sustain high glycolytic flux, includes sodium pyruvate 110 mg per liter as additional carbon source, designed for plaque assays viral growth and high density cultures where cell number reaches 10^

Ref: Dulbecco & Freeman Virology 1959 DMEM 3700 mg/L bicarbonate requires 10% CO2; ATCC media guide MEM RPMI DMEM comparison.

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Animal Tissue Culture 1

Phenol red in culture media is used as:

Visual pH monitoring without invasive electrodes that breach sterility risking bacterial contamination is accomplished via chemical indicator phenol red also called phenolsulfonphthalein, molecular weight 354.38 daltons, pKa 7.9 at 37°C making transition range 6.8 to 8.2 overlapping physiological pH of culture. Structure triphenylmethane dye exists in equilibrium between protonated yellow form absorbing maximally 430 nanometers and deprotonated red anionic form with extensive conjugated quinone system absorbing 560 nanometers, isosbestic point near 480 nanometers. At physiological pH mixture a

Ref: Freshney 7th ed phenol red pKa 7.9 indicator nontoxic; Sigma media phenolsulfonphthalein yellow red transition estrogenic caution.

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