Brains are most simply compared in terms of their size. The relationship between brain size , body size and other variables has been studied across a wide range of vertebrate species. As a rule, brain size increases with body size, but not in a simple linear proportion. In general, smaller animals tend to have larger brains, measured as a fraction of body size. For mammals, the relationship between brain volume and body mass essentially follows a power law with an exponent of about .  This formula describes the central tendency, but every family of mammals departs from it to some degree, in a way that reflects in part the complexity of their behavior. For example, primates have brains 5 to 10 times larger than the formula predicts. Predators tend to have larger brains than their prey, relative to body size. 
In the presence of air and various cofactors and enzymes, fatty acids are degraded to acetyl-CoA . The pathway is called beta-oxidation . Each cycle of beta-oxidation shortens the fatty acid chain by two carbon atoms and produces one equivalent each of NADH and one FADH 2 . The NADH and FADH 2 are used to generate ATP by oxidative phosphorylation. Dozens of ATP equivalents are generated by the beta-oxidation of a single long acyl chain.  The acetyl-CoA produced by beta-oxidation can be subsequently metabolized by the citric acid cycle, yielding further equivalents of ATP.