Dietary Connections

Glucose, though a simple energy source, is not common in the diets of humans and other animals. So, they obtain most of their energy from the digestion of carbohydrates like disaccharides and polysaccharides, proteins, and lipids.

Polysaccharide like glycogen, a chain of several glucose molecules, is first hydrolyzed into glucose and fed into glycolysis to produce pyruvate and high energy molecules.

A disaccharide like sucrose —a sugar found in most fruits and vegetables, is broken down into two simpler sugars, fructose and glucose, and both are then catabolized in the glycolytic pathway.

Proteins are first broken down into constituent amino acids. While most amino acids are recycled to build new proteins, others can undergo deamination and enter the glycolysis and citric acid cycle at different stages.

Lipids, like triglycerides, are catabolized into glycerol and fatty acids. The glycerol component is converted to a phosphorylated form that can enter glycolysis. While the fatty acid chains are converted by beta-oxidation to acetyl CoA, which then enters the citric acid cycle.