Fatty acids represent the principal form of stored energy for many organisms. There are two important advantages to storing energy in the form of fatty acids. The carbon in fatty acids is almost completely reduced compared to the carbon in other simple biomolecules. Therefore, oxidation of fatty acids will yield more energy (in the form of ATP) than any other form of carbon. Fatty acids are not generally as hydrated as monosaccharides and polysaccharides are, and thus they can pack more closely in storage tissues. | Chapter 24 Fatty Acid Catabolism to accompany Biochemistry, 2/e by Reginald Garrett and Charles Grisham All rights reserved. Requests for permission to make copies of any part of the work should be mailed to: Permissions Department, Harcourt Brace & Company, 6277 Sea Harbor Drive, Orlando, Florida 32887-6777 1 Outline Mobilization of Fats from Dietary Intake and Adipose Tissue Beta-Oxidation of Fatty Acids Odd-Carbon Fatty Acids Unsaturated Fatty Acids Other Aspects of Fatty Acid Oxidation Ketone Bodies 2 Why Fatty Acids? (For energy storage?) Two reasons: The carbon in fatty acids (mostly CH2) is almost completely reduced (so its oxidation yields the most energy possible). Fatty acids are not hydrated (as mono- and polysaccharides are), so they can pack more closely in storage tissues 3 Fat from Diet & Adipose Cells Triacylglycerols either way Triglycerides represent the major energy input in the modern American diet (but it wasn't always this way) Triglycerides are also the major form of stored energy in the body See Table Hormones (glucagon, epinephrine, ACTH) trigger the release of fatty acids from adipose tissue 4 Beta Oxidation of Fatty Acids Knoop showed that fatty acids must be degraded by removal of 2-C units Albert Lehninger showed that this occurred in the mitochondria F. Lynen and E. Reichart showed that the 2-C unit released is acetyl-CoA, not free acetate The process begins with oxidation of the carbon that is "beta" to the carboxyl carbon, so the process is called"beta-oxidation" 5 CoA activates FAs for oxidation Acyl-CoA synthetase condenses fatty acids with CoA, with simultaneous hydrolysis of ATP to AMP and PPi Formation of a CoA ester is expensive energetically Reaction just barely breaks even with ATP hydrolysis But subsequent hydrolysis of PPi drives the reaction strongly forward Note the acyl-adenylate intermediate in the mechanism! 6 Carnitine as a Carrier Carnitine carries fatty acyl groups across the inner | Chapter 24 Fatty Acid Catabolism to accompany Biochemistry, 2/e by Reginald Garrett and Charles Grisham All rights reserved. Requests for permission to make copies of any part of the work should be mailed to: Permissions Department, Harcourt Brace & Company, 6277 Sea Harbor Drive, Orlando, Florida 32887-6777 1 Outline Mobilization of Fats from Dietary Intake and Adipose Tissue Beta-Oxidation of Fatty Acids Odd-Carbon Fatty Acids Unsaturated Fatty Acids Other Aspects of Fatty Acid Oxidation Ketone Bodies 2 Why Fatty Acids? (For energy storage?) Two reasons: The carbon in fatty acids (mostly CH2) is almost completely reduced (so its oxidation yields the most energy possible). Fatty acids are not hydrated (as mono- and polysaccharides are), so they can pack more closely in storage tissues 3 Fat from Diet & Adipose Cells Triacylglycerols either way Triglycerides represent the major energy input in the modern American diet (but it wasn't always this way) .
