Sublime

This is the strange world of metabolic flux. Even a simple bacterial cell can undergo as many as a billion transformations per second,

All systems in the body are tightly regulated by specific hormones. Several key hormones regulate metabolism—the process by which the body converts food and drink into fuel. Ghrelin, also known as the hunger hormone, causes hunger. And peptide YY3–36 causes us to feel satisfied and stop eating. But insulin is by far the most important hormone when

The brain, just like a car, needs fuel. Our primary source of fuel is through fats, proteins, and carbohydrates in the diet. After digestion in the stomach, foodstuffs are absorbed into the bloodstream and circulate to various tissues and cells where they are broken down into even smaller particles. One of these particles is a two-carbon molecule

To live, an organism must metabolize: it must exchange matter and energy with its environment. Consequently, over the course of a year, many of the atoms in your body are replaced by new ones. The energy you use to get a drink of water comes from sunshine working its way up to you through the food chain—in a real sense, light lifts the cup to your

Much of the nitrogen within you was likely extracted from the air and embedded in ammonia in hot pressurized tanks. Today, crops grown with factory-made fertilizers feed billions of people. Without manufactured ammonia, the Earth’s population would be almost 50 percent smaller,25 and you and I might not be here. Our bodies each contain about four