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

Aulani "Biokimia" Presentation 6 Lipids: Hydrophobic molecules 4 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 A fatty acid

Aulani "Biokimia" Presentation 6 Building a fat molecule

Aulani "Biokimia" Presentation 6 4 Source of stored energy in living organisms 4 Lipids contain the elements carbon, hydrogen, and oxygen 4 Glycerol and fatty acids are the building blocks of lipids 4 Examples of lipids are fats and oils fatty acid glycerol

Aulani "Biokimia" Presentation 6 For simplicity, the fatty acids will be abbreviated as: glycerol + 3 fatty acids = a fat or oil + = makes a fatty acid and 3 water molecules, 3 H 2 O Since a fat or oil contains 3 fatty acid units, they are sometimes called triglycerides HOOC-R where "R" simply represents the long carbon chain.

Aulani "Biokimia" Presentation 6 Saturated and unsaturated fats

Aulani "Biokimia" Presentation 6 Phospholipids 4 One fatty acid replaced by phosphate PO Molecule has Hydrophilic head, and long hydrophobic tail. 4 Fatty acids unsaturated- remains fluid 4 Main component of cell membranes

Aulani "Biokimia" Presentation 6

Most Common Fatty Acids in Di- and Triglycerides Fatty acidCarbon:Double bondsDouble bonds Myristic14:0 Palmitic16:0 Palmitoleic16:1Cis-9 Stearic18:0 Oleic18:1Cis-9 Linoleic18:2Cis-9,12 Linolenic18:3Cis-9,12,15 Arachidonic20:4Cis-5,8,11,14 Eicosapentaenoic20:5Cis-5,8,11,14,17 Docosahexaenoic22:6Cis-4,7,10,13,16,19 CH 3 (CH 2 ) n COOH

Aulani "Biokimia" Presentation 6 Linolenic Acid Omega-3

Aulani "Biokimia" Presentation 6 Cell membrane- Phospholipid bilayer

Aulani "Biokimia" Presentation 6 Predominant Energy Pathways

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

Aulani "Biokimia" Presentation 6 Fat Metabolism 4 Mostly handled by the liver 4 Fats must first be broken down to form acetic acid which is subsequently oxidized. 4 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 Cholesterol 4 Structural basis of steroid hormones and vitamin D 4 Major building block plasma membranes 4 15% of cholesterol comes from diet the rest is made by the liver. 4 Cholesterol is lost by breakdown, secretion in bile salt and finally defecation

Aulani "Biokimia" Presentation 6 Lipoproteins 4 Fatty acids, fats, and cholesterol are insoluble in water and therefore are transported bound to small lipid-protein complexes called lipoproteins 4 Low-density lipoproteins (LDL) – transport cholesterol and other lipids to body cells 4 High-density lipoproteins (HDL) – transport cholesterol from tissue cells to liver for disposal 4 Ratio of HDL/LDL is important

Aulani "Biokimia" Presentation 6 Body Energy Balance 4 When energy intake and energy outflow are balanced – body weight remains stable 4 When they are not, weight is either lost or gained 4 Control of food intake: ? –Rising and falling blood levels of nutrients –Hormones –Body temperature –Psychological factors

Aulani "Biokimia" Presentation 6 Basal Metabolic Rate 4 The amount of heat produced by the body per unit of time under basal conditions 4 An average 155lb adult has a BMR of about kcal/hour

Aulani "Biokimia" Presentation 6 Lipids  Catabolism  Aerobic  transport of fatty acids from cytosol to mitochondria (role of carnitine)   -oxidation in mitochondria  4 steps  release of NADH and FADH 2  108 ATP/palmitic acid or 7 ATP/Carbon

Aulani "Biokimia" Presentation 6  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  Synthesis: lipogenesis  carried out by two cytosolic enzymes, acetyl-CoA carboxylase and fatty acid synthase  Requires: NADPH, ATP and biotin, CO 2  Sources of  Acetyl CoA - transfer of citrate from mitoch. to cytosol  NADPH - malic enzyme in cytosol - pentose phosphate pathway

Aulani "Biokimia" Presentation 6 Lipid Digestion - Rumen DigalDiglyMonogalDigly Galactose PropionateDiglyceride Glycerol TriglyerideFatty acids Saturated FA CaFACa ++ Feed particles  -galactosidase  -galactosidase Lipase Anaerovibrio lipolytica H + Reductases Lipase

Aulani "Biokimia" Presentation 6 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 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 Lipid Metabolism - In the Rumen

Aulani "Biokimia" Presentation 6 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. Microbial Fatty Acid Synthesis

Aulani "Biokimia" Presentation 6 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 acid mostly cellulolytic) (stearic and palmitate )

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

Aulani "Biokimia" Presentation 6 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 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 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 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 PalmiticPalmitoleic StearicOleic

Aulani "Biokimia" Presentation 6  Synthesis: lipogenesis  carried out by two cytosolic enzymes, acetyl-CoA carboxylase and fatty acid synthase  Requires: NADPH, ATP and biotin, CO 2  Sources of  Acetyl CoA - transfer of citrate from mitoch. to cytosol  NADPH - malic enzyme in cytosol - pentose phosphate pathway

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

Aulani "Biokimia" Presentation 6 4 If excess fat is consumed, there is no mechanism by which the body can increase its use of fat as a fuel. 4 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