Biochem 14: Glycolysis, Gluconeogenesis, and the Pentose Phosphate Pathway

Glucose is deceptively simple. In this episode, Medlock Holmes discovers that it is not a fuel with a single purpose, but a crossroads — a molecule whose fate depends entirely on context.We follow glucose as it enters the cell and encounters three competing narratives. In glycolysis, it is broken down rapidly to meet immediate energy demand. In gluconeogenesis, it is patiently rebuilt when supply must be secured. In the pentose phosphate pathway, it diverts sideways — not to generate ATP, but to produce reducing power and molecular building blocks.Drawing on Lehninger’s integrated pathway logic and Harper’s clinically oriented treatment of glucose handling and blood glucose control, this episode reveals how the same intermediates are reused, redirected, and regulated with precision. Regulation is shown not as on–off switches, but as layered decisions shaped by hormones, energy state, and tissue need.Medlock learns that metabolic pathways are not railways. They are conversations between past demand, present state, and future risk. Disorders of glucose metabolism arise not from ignorance of the pathways, but from failures of coordination.Here, biochemistry begins to resemble strategy.Key Topics Explored* Glycolysis as a central energy-yielding pathway* Gluconeogenesis and metabolic reversal* The pentose phosphate pathway and NADPH production* Shared intermediates and reciprocal regulation* Hormonal and allosteric control* Clinical relevance: hypoglycaemia, hyperglycaemia, and metabolic stress This is a public episode. If you'd like to discuss this with other subscribers or get access to bonus episodes, visit drmanaankarray.substack.com/subscribe