Chapter 25, part 2

1. Chapter 25, part 2 Metabolism and Energetics

2. SECTION 25-3Lipid Metabolism

3. Lipid catabolism • Lipolysis • Lipids broken down into pieces that can be converted into pyruvate • Triglycerides are split into glycerol and fatty acids • Glycerol enters glycolytic pathways • Fatty acids enter the mitochondrion

4. Lipid catabolism • Beta-oxidation • Breakdown of fatty acid molecules into 2-carbon fragments • Enter the TCA • Irreversible • Lipids and energy production • Cannot provide large amounts in ATP in a short amount of time • Used when glucose reserves are limited

5. Figure 25.9 Beta Oxidation Figure 25.9

6. Figure 25.9 Beta Oxidation Figure 25.9

7. Lipid synthesis (lipogenesis) • Almost any organic molecule can be used to form glycerol • Essential fatty acids cannot be synthesized and must be included in diet • Linoleic and linolenic acid

8. Figure 25.10 Lipid Synthesis Figure 25.10

9. Lipid transport and distribution • 5 types of lipoprotein • Lipid-protein complex that contains large glycerides and cholesterol • Chylomicrons • Largest lipoproteins composed primarily of triglycerides • Very low-density lipoproteins (VLDLs) • contain triglycerides, phospholipids and cholesterol

10. Lipid transport and distribution • 5 types of lipoprotein (continued) • Intermediate-density lipoproteins (IDLs) • Contain smaller amounts of triglycerides • Low-density lipoproteins (LDLs) • Contain mostly cholesterol • High-density lipoproteins (HDLs) • Equal amounts of lipid and protein

11. Lipoprotein lipase • Enzyme that breaks down complex lipids • Found in capillary walls of liver, adipose tissue, skeletal and cardiac muscle • Releases fatty acids and monglycerides

12. Figure 25.11 Lipid Transport and Utilization Figure 25.11a

13. Figure 25.11 Lipid Transport and Utilization Figure 25.11b

14. SECTION 25-4Protein Metabolism

15. Amino acid catabolism • If other sources inadequate, mitochondria can break down amino acids • TCA cycle • removal of the amino group (-NH2) • Transamination – attaches removed amino group to a keto acid • Deamination – removes amino group generating NH4+ • Proteins are an impractical source of ATP production

16. Figure 25.12 Amino Acid Catabolism Figure 25.12

17. Figure 25.12 Amino Acid Catabolism Figure 25.12a

18. Figure 25.12 Amino Acid Catabolism Figure 25.12b

19. Figure 25.12 Amino Acid Catabolism Figure 25.12c

20. Protein synthesis • Essential amino acids • Cannot be synthesized by the body in adequate supply • Nonessential amino acids • Can be synthesized by the body via amination • Addition of the amino group to a carbon framework

21. Figure 25.13 Amination Figure 25.13

22. Figure 25.14 A Summary of the Pathways of Catabolism and Anabolism Figure 25.14

23. SECTION 25-5Nucleic Acid Metabolism

24. Nucleic acid metabolism • Nuclear DNA is never catabolized for energy • RNA catabolism • RNA molecules are routinely broken down and replaced • Generally recycled as nucleic acids • Can be catabolized to simple sugars and nitrogenous bases • Do not contribute significantly to energy reserves

25. Nucleic acid synthesis • Most cells synthesis RNA • DNA synthesized only when preparing for division