All systems ↗Glucose is trapped
Hexokinase or liver/pancreatic glucokinase forms glucose-6-phosphate, committing imported glucose to intracellular metabolism.
CELLULAR ENERGY / 02
Glucose carbon takes more than one route.
Glycolysis supplies ATP, pyruvate, redox transfer, and biosynthetic intermediates. Lactate connects cells and organs; gluconeogenesis helps maintain circulating glucose during fasting rather than simply “reversing glycolysis.”
Investment precedes payoff
Early reactions spend ATP; later substrate-level phosphorylation produces ATP and NADH with a net gain per glucose.
Pyruvate is a junction
Pyruvate can enter mitochondria, interconvert with lactate, support alanine exchange, or contribute to glucose synthesis in appropriate organs.
NAD+ must return
Glyceraldehyde-3-phosphate oxidation requires NAD+. Shuttles or lactate dehydrogenase help reoxidize cytosolic NADH.
Lactate is transferable fuel
Lactate moves through monocarboxylate transporters and can be oxidized by heart, muscle, and other tissues.
Red cells require glycolysis
Without mitochondria, mature red blood cells depend on glycolysis and export lactate while using ATP to preserve membrane function.
Liver and kidney make glucose
During fasting, gluconeogenic organs use lactate, glycerol, and selected amino-acid carbon to support blood glucose.
The pathway spends energy
Gluconeogenesis bypasses irreversible glycolytic steps and consumes high-energy phosphates; fat oxidation often helps supply that energy.