Milk Composition & Synthesis
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Milk Synthesis
Lactose

FATES OF GLUCOSE IN THE MAMMARY GLAND

Glucose is an absolute requirement for milk synthesis with over two thirds of the glucose utilized by mammary epithelial cells being used for lactose synthesis. Intracellular glucose concentrations in mammary tissue are rate-limiting for lactose synthesis. In addition, a substantial proportion of the remaining glucose is metabolized in pathways leading to glycerol synthesis and to pentose production, the latter resulting in generation of reducing equivalents for fatty acid synthesis and ribose molecules for RNA and DNA synthesis.

In the cow, some is metabolized by the cells for energy (generation of ATP), some is used for synthesis of glycerol (used for milk triglyceride synthesis), 20-30% goes through the pentose phosphate shunt which generates NADPH (used as reducing equivalents in milk fatty acid synthesis), produces ribose (used in DNA and RNA synthesis), and 60-70% is used for lactose synthesis