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Chapter 17

Chapter 17. Fat Catabolism. Fatty Acid Catabolism. Key topics : To Know. How fats are digested in animals How fats are mobilized and transported in tissues How fats are oxidized as a source of energy How “ketone bodies” are produced and used.

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Chapter 17

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  1. Chapter 17 Fat Catabolism

  2. Fatty Acid Catabolism Key topics: To Know • How fats are digested in animals • How fats are mobilized and transported in tissues • How fats are oxidized as a source of energy • How “ketone bodies” are produced and used

  3. Oxidation of fatty acids is a major energy source in many organisms • About one-third of our energy needs comes from dietary triacylglycerols • About 80% of energy needs of mammalian heart and liver are met by oxidation of fatty acids • Many hibernating animals, such as grizzly bears, rely almost exclusively on fats as their source of energy • Some animals (camels) store fat as an eventual source of water

  4. Fats provide efficient fuel storage • The advantage of fats over polysaccharides: • Fatty acids carry more energy per carbon because they are more reduced • Fatty acids carry less water along because they are nonpolar • Glucose and glycogen are for short-term energy needs, quick delivery • Fats are for long-term (months) energy needs, good storage, slow delivery

  5. Fat Storage in White Adipose Tissue

  6. Lipid Digestion

  7. Chylomicron

  8. Mobilization of Fat from Adipose Tissue

  9. Guinea Pig Adipocytes

  10. Entry of Glycerol into Glycolysis

  11. Energetics of Glycerol as An Energy Source Glycerol kinase - ATP Glycerol-3-P DH + NADH 3-P-Gyld DH + NADH 3-PGA Kinase + ATP Pyr Kinase + ATP Total = 1 ATP + 2 NADH Can GLYCEROL be FERMENTED? Explain

  12. Major Fatty Acid Oxidation = β-Oxidation Occurs in the Mitochondrion

  13. β-OxidationOverall Flow

  14. One Round (a) and Further Rounds (b) of β-Oxidation EOC Problem 4: explores numbers of round of β-oxidation. EOC Problem 9: Compartmentalization of β-oxidation.

  15. EOC Problem 3 Compares β-oxidation with the Citric Acid Cycle

  16. Hibernating Animals Rely upon β-Oxidation for their Sleep EOC Problems 13, 26 and 28: Deals with Fat as Storage of Water and Energy. Please keep in mind Prof Makemson spent a good portion of his life in the Middle East…fat as storage of water!!

  17. Energetics of Oxidation of Palmitic Acid *Assumes 1 NADH = 2.5 ATP, and 1 FADH2 = 1.5 ATP from Respiratory Electron Transport EOC Problems 1 and 2 deals with amount of energy stored in fat and how long it can last?

  18. Oxidation of Unsaturated Fatty Acids (Remember they are cis!)

  19. Multiple points of unsaturation can require energy to get them through β-Oxidation

  20. β-Oxidation of Odd Numbered Fatty Acids Results in Propionyl-SCoA

  21. Plant vs Animalβ Oxidation Peroxisomes in Animals – mainly different in First Step and Usually use >20 C and branched chain fatty acids. Peroxisomes in Plants are main fatty acid oxidation (not in mitochondria)

  22. Seeds are Loaded with Fats and Oils

  23. Arrangement of the β-Oxidation Enzymes

  24. Eukaryotes Also have 2 Arrangements of these Enzymes

  25. ω-Oxidation in the ER of Liver Cells Minor pathway in mammals, more important in invertebrates ω = Omega, the last letter in the Greek alphabet

  26. α-Oxidation of Branched Chain Fatty Acids Takes Place in Peroxisomes

  27. β-oxidation of Odd Numbered Fatty Acids … last round produces 1 Ac-SCoA and 1 Propionyl-SCoA

  28. Formation of Ketone Bodies Occurs in the Liver Isoprenes and Steroids

  29. Oxidation of Ketone Bodies by Non-hepatic Tissues

  30. Requires Glucogenic Intermediates, Glucose can not be made from Ac-SCoA EOC Problem 16: About use of fatty acids in Diabetics.

  31. Things to Know and Do Before Class • Review structure of fat, general concepts of digestion of fat. • Role of glucagon to mobilize fat utilization. • Activation of fatty acids in cytoplasm for their oxidation in the mitochondrion. • Know the steps of β-oxidation…and what is involved for the complete oxidation of the fatty acids to CO2 and water. • Know that unsaturated fatty acids are oxidized, but energy output is different (which way?). • Know that other forms of fatty acid oxidation exist. • Know how ketone bodies are made and used. • EOC Problems: 1-4, 9, 10, 13, 16, 26, 28.

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