Human Biochemistry Volume 1 - Murray R. 1993

Bioenergetics and Carbohydrate and Lipid Metabolism
Gluconeogenesis and the Pentose Phosphate Pathway
Gluconeogenesis - Biomedical Significance

Gluconeogenesis meets the body's glucose requirements when dietary carbohydrate intake is insufficient. A continuous supply of glucose as an energy source is particularly vital for The Nervous system and erythrocytes. A drop in Blood glucose below a certain critical level impairs Brain function; severe hypoglycemia leads to coma and can result in death. Glucose is also essential for adipose tissue as a source of glycerol, a component of glycerides, and likely plays a crucial role in maintaining effective concentrations of Citric Acid Cycle intermediates in many Tissues. Consequently, even when the body's caloric needs are met primarily by fat, a baseline demand for glucose always persists. Furthermore, Glucose serves as the sole fuel for Skeletal Muscle during anaerobic exertion. It is the precursor to milk sugar (lactose) in the Mammary Glands and is actively consumed by the developing fetus. It should also be noted that gluconeogenesis serves to clear tissue metabolites from the blood, such as lactate produced in Muscles and erythrocytes, and glycerol continuously released from adipose tissue. Propionate—the principal glucogenic fatty acid generated during carbohydrate Digestion in ruminants—serves as the primary substrate for gluconeogenesis in these animals.