Biological Chemistry - Berezov T. T., Korovkin B. F. 1998

Nervous tissue
Metabolic features of nervous tissue
Carbohydrate metabolism

The primary substrate for Brain tissue Respiration is glucose. On average, 100 g of brain tissue consumes 5 mg of glucose per minute. It is estimated that more than 90% of the glucose utilized in brain tissue is oxidized to CO2 and H2O via The Tricarboxylic Acid Cycle. Under physiological conditions, the Pentose Phosphate Pathway of glucose oxidation plays a minor role in brain tissue, although this metabolic pathway is intrinsic to all brain Cells. The reduced form of NADP (NADPH) generated during The pentose phosphate cycle is utilized for the synthesis of Fatty acids and Steroids. Interestingly, the total glucose content across the entire brain mass is approximately 750 mg. Brain tissue oxidizes 75 mg of glucose per minute. Consequently, The amount of glucose present within the brain tissue alone would be sufficient to sustain human life for only about 10 minutes. This calculation, along with the arteriovenous glucose difference, proves that Blood Glucose serves as the primary respiratory substrate for the brain. Apparently, glucose readily diffuses from the blood into the brain tissue (with a glucose concentration of 0.05% in the brain tissue compared to 4.44 mmol/L, or 80 mg/100 mL, in arterial blood).

A close relationship exists between brain tissue glucose and Glycogen, demonstrated by the fact that when glucose supply from the blood is insufficient, brain glycogen acts as a source of glucose, whereas excess glucose serves as a precursor for glycogen synthesis. Glycogen breakdown in brain tissue occurs via phosphorolysis mediated by the cAMP system. Overall, however, the utilization of glycogen in the brain plays a negligible energetic role compared to glucose, owing to the relatively low glycogen content in the brain.

Alongside aerobic Carbohydrate METABOLISM, brain tissue is capable of fairly intensive anaerobic Glycolysis. The Significance of this phenomenon remains insufficiently understood, as glycolysis as an energy source cannot by any means match the efficiency of tissue respiration in the brain.

* Overall, resting oxygen consumption by adult human Tissues is 200-240 mL/min.



Last update: 06/08/2026

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