1 / 38

Lipid Biochemistry

Lipid Biochemistry. Aulanni’am Biochemistry Laboratory Chemistry Department Brawijaya University. Lipids: Hydrophobic molecules. Fats (animal) and Oils (plant) - energy storage, insulation Fatty acid - Long hydrocarbon tail with carboxly -COOH group at the head.

red
Download Presentation

Lipid Biochemistry

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Lipid Biochemistry Aulanni’am Biochemistry Laboratory Chemistry Department Brawijaya University Aulani "Biokimia" Presentation 6

  2. Lipids: Hydrophobic molecules • Fats (animal) and Oils (plant) - energy storage, insulation • Fatty acid - Long hydrocarbon tail with carboxly -COOH group at the head. • Saturated - no double bonds; saturated with H • Unsaturated - one or more H replaced by double bond - stays liquid • Carboxyl groups on fatty acid link to -OH group on a 3-carbon alcohol (glycerol) Aulani "Biokimia" Presentation 6

  3. A fatty acid Aulani "Biokimia" Presentation 6

  4. Building a fat molecule Aulani "Biokimia" Presentation 6

  5. fatty acid glycerol • Source of stored energy in living organisms • Lipids contain the elements carbon, hydrogen, and oxygen • Glycerol and fatty acids are the building blocks of lipids • Examples of lipids are fats and oils Aulani "Biokimia" Presentation 6

  6. For simplicity, the fatty acids willbe abbreviated as:   HOOC-R where "R" simply represents thelong carbon chain. glycerol        +        3 fatty acids         =         a fat or oil +                      =  makes a fatty acid and 3 water molecules, 3 H2O Since a fat or oil contains 3 fatty acid units, they are sometimes called triglycerides Aulani "Biokimia" Presentation 6

  7. Saturated and unsaturated fats Aulani "Biokimia" Presentation 6

  8. Phospholipids • One fatty acid replaced by phosphate PO4- • Molecule has Hydrophilic head, and long hydrophobic tail. • Fatty acids unsaturated- remains fluid • Main component of cell membranes Aulani "Biokimia" Presentation 6

  9. Aulani "Biokimia" Presentation 6

  10. Most Common Fatty Acids in Di- and Triglycerides CH3(CH2)nCOOH Aulani "Biokimia" Presentation 6

  11. Linolenic Acid Omega-3 Aulani "Biokimia" Presentation 6

  12. Cell membrane- Phospholipid bilayer Aulani "Biokimia" Presentation 6

  13. Predominant Energy Pathways Aulani "Biokimia" Presentation 6

  14. We use fat in the form of triglyceride (3 fatty acids and 1 glycerol). Aulani "Biokimia" Presentation 6

  15. Fat Metabolism • Mostly handled by the liver • Fats must first be broken down to form acetic acid which is subsequently oxidized. • Oxidation (breakdown) of fats is not always complete. Intermediate products accumulate in the blood causing the blood to become acidic (acidosis or ketosis) Aulani "Biokimia" Presentation 6

  16. Cholesterol • Structural basis of steroid hormones and vitamin D • Major building block plasma membranes • 15% of cholesterol comes from diet the rest is made by the liver. • Cholesterol is lost by breakdown, secretion in bile salt and finally defecation Aulani "Biokimia" Presentation 6

  17. Lipoproteins • Fatty acids, fats, and cholesterol are insoluble in water and therefore are transported bound to small lipid-protein complexes called lipoproteins • Low-density lipoproteins (LDL) – transport cholesterol and other lipids to body cells • High-density lipoproteins (HDL) – transport cholesterol from tissue cells to liver for disposal • Ratio of HDL/LDL is important Aulani "Biokimia" Presentation 6

  18. Body Energy Balance • When energy intake and energy outflow are balanced – body weight remains stable • When they are not, weight is either lost or gained • Control of food intake: ? • Rising and falling blood levels of nutrients • Hormones • Body temperature • Psychological factors Aulani "Biokimia" Presentation 6

  19. Basal Metabolic Rate • The amount of heat produced by the body per unit of time under basal conditions • An average 155lb adult has a BMR of about 60-72 kcal/hour Aulani "Biokimia" Presentation 6

  20. Lipids • Catabolism • Aerobic • transport of fatty acids from cytosol to mitochondria (role of carnitine) • -oxidation in mitochondria • 4 steps • release of NADH and FADH2 • 108 ATP/palmitic acid or 7 ATP/Carbon Aulani "Biokimia" Presentation 6

  21. Catabolism: dietary lipids • Digestion: a) Slow relative to carbohydrates b) In small intestine with action of bile salts c) FAcs absorbed across intestinal wall and reconverted to TAGs d) Transported as chylomicrons • Mobilisation from adipocytes: a) FAcs transported in blood bound to serum albumin; dissociates in cells  oxidation b) glycerol undergoes glycolysis • Role of glucose 6-phosphatase in maintaining blood glucose levels (in the liver, not the muscles) Aulani "Biokimia" Presentation 6

  22. Synthesis: lipogenesis • carried out by two cytosolic enzymes, acetyl-CoA carboxylase and fatty acid synthase • Requires: NADPH, ATP and biotin, CO2 • Sources of • Acetyl CoA - transfer of citrate from mitoch. to cytosol • NADPH - malic enzyme in cytosol - pentose phosphate pathway Aulani "Biokimia" Presentation 6

  23. Lipid Digestion - Rumen -galactosidase DigalDigly MonogalDigly Galactose Propionate Diglyceride Glycerol Triglyeride Fatty acids Saturated FA CaFA Ca++ Feed particles -galactosidase Lipase Anaerovibrio lipolytica H+ Reductases Lipase Aulani "Biokimia" Presentation 6

  24. Fat Digestion • Digestibility influenced by: • Dry matter intake • Decreases with greater intake • Amount of fat consumed • Digestibility decreases 2.2% for each 100 g of FA intake (Response is variable) • Degree of saturation • Digestibility decreases with increased saturation • Maximal digestion with fats having Iodine values greater than 40 Aulani "Biokimia" Presentation 6

  25. Lipid Metabolism - In the Rumen • 1. Minimal degradation of long-chain fatty acids in • the rumen • Fatty acids not a source of energy to microbes • 2. Active hydrogenation of unsaturated fatty acids • 3. Microbial synthesis of long-chain fatty acids in • the rumen (15g/kg nonfat org matter fermented) • 4. No absorption of long chain fatty acids from the rumen • More fat leaves the rumen than consumed by the animal • Lipids leaving the rumen • 80 to 90% free fatty acids attached to feed particles • and microbes • ~10% microbial phospholipids leave the rumen • Small quantity of undigested fats in feed residue Aulani "Biokimia" Presentation 6

  26. Microbial Fatty Acid Synthesis • Synthesize C 18:0 and C 16:0 in 2:1 ratio using • acetate and glucose (straight-chain even carbon #). • If propionate or valerate used, straight-chain odd • carbon fatty acids synthesized. • Branched-chain VFA used to produce branched • chain fatty acids. • About 15 to 20% of microbial fatty acids are mono- • unsaturated. No polyunsaturated fatty acids are • synthesized. • Some incorporation of C 18:2 into microbial lipids. Aulani "Biokimia" Presentation 6

  27. Hydrogenation of Fatty Acids in the Rumen Polyunsaturated fatty acids (all cis) Isomerase (from bacteria) Needs free carboxyl group and diene double bond Shift of one double bond (cis & trans) Hydrogenation Hydrases (from bacteria, Hydrogenated fatty acidmostly cellulolytic) (stearic and palmitate) Aulani "Biokimia" Presentation 6

  28. Hydrogenation of Fatty Acids in the Rumen • All unsaturated fatty acids can be hydrogenated • Monounsaturated less than polyunsaturated • 65 to 96% hydrogenation • Numerous isomers are produced • Biohydrogenation is greater when high forage • diets fed • Linoleic acid depresses hydrogenation of FA Aulani "Biokimia" Presentation 6

  29. Conjugated Linoleic Acid - RumenMost Common Pathway (High Roughage) Linoleic acid (cis-9, cis-12-18:2) Conjugated linoleic acid (CLA, cis-9, trans-11- 18:2) Vaccenic acid (Trans-11-18:1) Stearic acid (18:0) Cis-9, trans-12 isomerase Butyrivibrio fibrosolvens Aulani "Biokimia" Presentation 6

  30. CLA Isomers - Rumen (High Concentrate) Low Rumen pH Linoleic acid (cis-9, cis-12-18:2) Cis-9, trans-10 isomerase CLA Isomer (trans-10, Cis-12-18:2) This isomer is inhibitory to milk fat synthesis. Trans-10-18:1 Aulani "Biokimia" Presentation 6

  31. Linolenic Acid – Oleic Acid Linolenic acid (cis-9, cis-12, cis-15-18:3) (Cis-9, trans-11, cis-15-18:3) Trans-11, cis-15-18:2 Trans-11-18:1 (vaccenic acid) Oleic acid cis-9 (18:1) Stearic acid (18:0) Aulani "Biokimia" Presentation 6

  32. CLA absorbed from the intestines available for incorporation into tissue triglycerides. Reactions from linoleic acid to vaccinic acid occur at a faster rate than from vaccinic acid to stearic acid. Therefore, vaccinic acid accumulates in the rumen and passes into intestines where it is absorbed. Quantities of vaccinic acid leaving the rumen several fold greater than CLA. Aulani "Biokimia" Presentation 6

  33. Conversion of Vaccinic Acid to CLA • In mammary gland and adipose • Trans-11-18:1 CLA, cis-9, trans-11 18:2 • Stearoyl CoA Desaturase • ‘9-desaturase’ • This reaction probably major source of CLA in • milk and tissues from ruminants. • Also transforms • Palmitic Palmitoleic • Stearic Oleic Aulani "Biokimia" Presentation 6

  34. Synthesis: lipogenesis • carried out by two cytosolic enzymes, acetyl-CoA carboxylase and fatty acid synthase • Requires: NADPH, ATP and biotin, CO2 • Sources of • Acetyl CoA - transfer of citrate from mitoch. to cytosol • NADPH - malic enzyme in cytosol - pentose phosphate pathway Aulani "Biokimia" Presentation 6

  35. Synthesis: lipogenesis • Other roles of PPP • alternative pathway for glucose metabolism • production of ribose 5-phosphate (nucleotide synthesis) • Ketone bodies arise from the overflow pathway in liver; major source of energy for heart, muscle and brain (fasting and diabetes) • Location of lipid metabolism • oxidation in mitoch., synthesis in cytosol Aulani "Biokimia" Presentation 6

  36. Summary of fatty acid metabolism in the liver Aulani "Biokimia" Presentation 6

  37. If excess fat is consumed, there is no mechanism by which the body can increase its use of fat as a fuel. • Instead, when excess fat calories are consumed, the only option is to accumulate the excess fat as an energy store in the body, and this process occurs at a low metabolic cost and is an extremely efficient process. Aulani "Biokimia" Presentation 6

  38. thank you to be continued .... Aulani "Biokimia" Presentation 6

More Related