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Life in the Fat Lane

The Chemistry of Bear Hibernation

By Scott J. Donnelly

Life in the Fat Lane



This interrupted case study examines one of nature’s metabolic marvels: the hibernating bear and the fat catabolism pathway that enables it to survive the long, cold, and foodless winter months. After a brief introduction explaining the basics of bear hibernation, the case describes how bears oxidize saturated free fatty acids in a four-step, enzyme-dependent pathway to produce acetyl coenzyme A, which enters the citric acid cycle to eventually produce more ATP. As students work through a variety of scaffolded questions (e.g., multiple choice, true/false, short answer, and rudimentary calculations), they gain foundational knowledge about the molecular structure of fats and fatty acids, the structural forms of electron transport coenzyme molecules NAD+ and FAD, oxidation-reduction characteristics in organic reactions, and the enzymes that are needed to carry out specific chemical reactions. The case is designed to be used in lower- and upper-level undergraduate organic chemistry or biochemistry classes. Before beginning the case, students should have an understanding of fatty acids and know that fatty acid chain lengths vary.


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  • Indicate whether a fatty acid substrate is oxidized or reduced, and whether an enzyme is an oxidizing or reducing agent.
  • Categorize a fatty acid side chain as being saturated or unsaturated and calculate its length.
  • Calculate the change in unsaturation of a fatty acid substrate when oxidized or reduced.
  • Evaluate how the molecular geometry (shape) of a fatty acid substrate changes when the substrate is oxidized or reduced.
  • Assess how the type of functional group influences reaction chemistry.
  • Identify the type of enzyme required to change a fatty acid substrate into something else.


Bears; hibernation;  organic chemistry; fats; metabolism; enzyme; coenzyme; fatty acid; redox; catabolism


Subject Headings

Organic Chemistry


Undergraduate lower division, Undergraduate upper division












Directed, Discussion, Interrupted



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