Metabolism & Chemical Reactions

Your body continuously conducts metabolic activities that sustain life. At a fundamental level, your metabolism is the sum total of countless chemical reactions that fall into two broad categories. Those that build complex chemicals from simpler starting materials are termed anabolic reactions. The chemical breakdown of substances into simpler molecules is called catabolism. The chemical reactions that constitute your metabolism are constantly in flux, adjusting to the changing conditions of your body and your nutritional status.

Sugar Trapping: Phosphorylation

Dominant chemical reactions involved in carbohydrate metabolism include the breakdown of sugars and production of fat and the glucose-storage molecule glycogen. These processes occur when sugars are absorbed from your bloodstream into your cells. Upon absorption into a cell, sugars undergo a chemical reaction called phosphorylation, which prevents them from leaking back into your circulation. Phosphorylated sugars are channeled into different chemical pathways depending on your body's metabolic needs.

Sugar Metabolism

Glycolysis is the series of chemical reactions wherein glucose is broken down to generate energy. The sugar galactose is chemically transformed into an intermediate molecule, which also enters into the glycolysis pathway. The sugar fructose does not undergo glycolysis; it is diverted into fat production. Extra glucose that is not needed for immediate energy production is chemically "banked" in the form of glycogen. The chemical reactions involved in glycogen formation reverse to release glucose when your body requires energy.

Protein Synthesis

Whereas the overarching objective of carbohydrate metabolism is ensuring a constant energy supply for your body, the dominant aspect of protein metabolism is production of needed enzymes, transporters, messengers, structural substances and other function-specific proteins. Your genes contain the "recipes" for roughly 20,000 proteins. The amino acid-building blocks used to construct proteins are absorbed from your diet or manufactured within your body. All cells in your body have the chemical capacity to produce proteins; the specific proteins produced depends on the cell type. Your liver manufactures a large quantity of transporter proteins and the coagulation factors, which are essential for blood clotting.

Protein-Glucose Link

When glucose is in short supply, proteins from your muscles and organs are broken down into their constituent amino acids, most of which can be chemically converted into molecules that can be used to manufacture glucose. This chemical process, known as gluconeogenesis, is crucial to survival during periods of starvation.

Fat Storage and Oxidation

Fat tissue is your body's long-term energy-storage depot. Dietary fats not immediately needed by your tissues are chemically processed in your liver to form triglycerides, which are secreted into your bloodstream and absorbed by your fat cells. The triglycerides remain in your fat cells until your body needs energy. Hormones stimulate the chemical breakdown of stored triglycerides, releasing fatty acids. A series of chemical reactions called fatty acid oxidation generates energy.