This chapter describes the basic biochemistry
of humans, specifically how humans use sugars
and fats as energy and how it actually functions
to power muscle movements, power the heart,
power nerve signals, and power biochemical
reactions. In many respects, life as we know it
is these amazing energy reactions. These are
the reactions of life. A dead cell does not generate
or use energy, and a living cell relies on its
energy sources. Here we describe how energy
is generated by living cells and how it is used.
Figure 1.3.1 outlines the different biochemical
pathways that run human and animal energetics,
provide energy when needed, and use
energy for storing vital molecules. The central
pathways are “glycolysis,” “ß-oxidation,” and
the “citric acid cycle,” or the breaking down of
glucose to two molecules of pyruvate, and then
using pyruvate and breaking down fats by
ß-oxidation to generate reduced nicotinamide
adenine dinucleotide (NADH), a derivative of
the vitamin niacin, and reduced flavin adenine
dinucleotide (FADH2), a derivative of the vitamin
riboflavin, which both drive oxidative phosphorylation
or energy generatio