Fatty acid metabolism

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Fatty acids are a source of metabolic energy to be used by muscle cells during exercise. Ingested fats are digested and used as an immediate source of energy by respiring cells or stored in adipocytes (fat cells) as fat droplets[1].

During a prolonged period of exercise, energy stored as fat droplets in adipocytes is mobilised as glycogen stores are used up. Epinephrine or glucagon bind to receptors on adipocyte cell membranes and initiate a secondary messenger response. Adenylyl cyclase is activated to convert ATP to cAMP, which in turn binds to Protein Kinase A and activates it. Activated Protein Kinase activates Triglycerol Lipases which break down triglycerols into three fatty acid molecules[2].

Fatty acid molecules are taken up by the serum albumin in the bloodstream. The fatty acid molecules are transported to respiring muscle cells to undergo β-oxidation. This reaction produces ATP and carbon dioxide [3].

Triacylglycerols Triacylglycerols are reduced and anhydrous which means they are highly concentrated stores of metabolic energy. The yield of the complete oxidation of fatty acids is higher than carbohydrates and proteins at 9kcal/g. [4]


  1. http://www.wiley.com/college/boyer/0470003790/animations/fatty_acid_metabolism/fatty_acid_metabolism.htm
  2. http://www.wiley.com/college/boyer/0470003790/animations/fatty_acid_metabolism/fatty_acid_metabolism.htm
  3. http://www.wiley.com/college/boyer/0470003790/animations/fatty_acid_metabolism/fatty_acid_metabolism.htm
  4. Stryer, L.(1995) Biochemistry, fourth edition, New York: W.H. Freeman and company, pp. 605
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