LEMAK : Struktur , Fungsi dan Metabolisme

1. Artharini I LEMAK : Struktur, FungsidanMetabolisme

2. LEMAK ??? kolesterol Obesitas Hipertensi diabetes Jantung

3. Health issues • Excessive dietary fat intake is associated with obesity, diabetes, cancer, hypertension and atherosclerosis. • Not more than 35% of energy intake should come from fat. Saturated fat should not make up more than 15% of the total fat intake. • Omega-3 fatty acids (20 carbons) from fish may protect against atherosclerosis. American Heart association recommends 2-3 fish meals per weak. Fish oil supplements should be avoided because they may be contain concentrated toxins accumulated by the fish.

4. DEFINISI LEMAK • Senyawa yang larutdalampelarutlemak, sepertikloroform, benzena, hexan, asetondaneter. • Ester asamlemakdangliserol (trigliserida) • Bentuk padat : lemak  cair : minyak Kenapaenerginyalebihtinggi?

5. Kandungan C, H dan O C H O Lemak 77 12 11 Pati 44 6 50

6. Komponenstrukturalmembransel • Sebagaisumberenergi, umumnyadalambentuktrigliserida • Pelarut vitamin yglarutpadalemak • Sebagaiprekursorbiosintetik ( hormon steroid darikolesterol) • Untukmemproteksi (contohmelapisiginjal) • Untukinsulasipanas FUNGSI:

7. SIFAT UMUM LEMAK Relatiftidaklarutdalam air Larutdalampelarut non polar (eter, kloroform) Merupakankonstituenmakananygpenting ( energinyalebihtinggi, adanya vitamin larutdlmlemak, asamlemakessensial) Disimpandijaringanadiposa insulator panas Kombinasi lipid dengan protein  alatpengangkut lipid dlmdarah

8. KLASIFIKASI LEMAK (Harper) • LIPID SEDERHANA Ester asamlemakdenganberbagaialkohol - Lemak (fat) : ester as. Lemakdengangliserol; minyak (oil) lemakdlmkondisicair - wax (malam) : ester asamlemak dg alkoholmonohidratberberatmolekultinggi 2. LIPID KOMPLEKS Ester asamlemakygmgd gugus2 selainalkoholdanasamlemak - Fosofolipid - Glikolipid - lipid kompleks lain (sulfolipid, aminolipid) • PREKURSOR DAN LIPID TURUNAN -asamlemak, gliserol, steroid, alkohol lain, aldehidlemak,badanketon, hidrokarbon, vitamin larutlemakdanhormon.

9. Classification • Bloor’s Classification • A. Simple lipid - ester of fatty acids with various alcohols • 1. Natural fats and oils (triglycerides) • 2. Waxes • (a) True waxes: cetyl alcohol esters of fatty acids • (b) Cholesterol esters • (c) Vitamin A esters • (d) Vitamin D esters • Compound lipid - esters of fatty acids with alcohol plus other groups • 1. Phospholipids and spingomyelin: contains phosphoric acid and often a nitrogenous base • 2. Spingolipids (also include glycolipids and cerebrosides): contains aminoalcoholspingosine, carbohydrate, N-base; glycolipids contains no phosphate • 3. Sulfolipids : contains sulfate group • 4. Lipoproteins : lipids attached to plasma/other proteins • 5. Lipopolysaccharides: lipids attached to polysaccharides

10. Classification cont. • Derived lipids – hydrolytic products of A & B with lipid characters • 1. Saturated & unsaturated fatty acids • 2. Monoglycerides and diglycerides • 3. Alcohols (b-carotenoid ring, e.g., vitamin A, certain carotenoids) • Miscellaneous lipids • 1. Aliphatic hydrocarbons: found in liver fat and certain hydrocarbon found in beeswax and plant waxes • 2. Carotenoids • 3. Squalene : found in shark and mammalian liver and in human sebam; an important intermediate in biosynthesis of cholesterol • 4. Vitamin E and K

11. ReaksiPembentukanLemak CH2OH HOOC-R CH2-OOC-R CHOH + HOOC-R --- CH-OOC-R + 3H2O CH2OH HOOC-R CH2-OOC-R Gliserolasamlemaklemakair

12. Nomenclature and Structure • Fats and oils: • Vegetable oils are triglycerides that are liquid at room temp due to their higher unsaturated or shorter-chain fatty acids • Triglycerides are most abundant natural lipids • Natural fats have D-configuration • Usually R1 and R3 are saturated and R2 is unsaturated • Natural fats are mixture of two or more simple triglycerides

13. Fatty acids “ A fatty acid may be defined as an acid that occurs in a natural triglyceride and is a mono carboxylic acid ranging in chain length From four carbon to 24 carbon atoms and including , with exceptions, only the even-numbered members of the series ”

16. Ditentukan o/ susunan as.lemaknya: • Jenuh/saturated (CnH2nO2) • Tidak jenuh/unsaturated (CnH2n-xO2) • Punya 2 atau lebih molekul H yg hilang • Esensial bagi tubuh SIFAT

19. Most Common Fatty Acids in Di- and Triglycerides CH3(CH2)nCOOH

20. Sumber : Lehninger,

21. Sumber : Lehninger,

22. Sumber : Lehninger,

23. Fatty Acid Isomers

24. Lipid Content of Feeds • Forages • Fat content is low: 1 to 4% of dry matter • High proportion of linolenic acid (18:3) • Diglycerides in fats of leaves • Grains • Fat content variable: 4 to 20% of dry matter • High proportion of linoleic acid (18:2) • Triglycerides in oils of seeds

25. Sumber : Lehninger,

26. REAKSI KIMIA & SIFAT KHAS LEMAK • HIDROLISIS • ENZIMATIK trjddlmpencernaan • DG ALKALI (PENYABUNAN) Lipida+alkaligliserol grm alkali as.lemak

27. REAKSI KIMIA & SIFAT KHAS LEMAK 2. ANALISIS • Bil.Penyabunan adalah jml mg KOH u/menyabunkan 1 gr lemak • Bil.As adalah jml mg KOH u/menetralkan as.lemak bebas dr 1 gr lemak • Bil.Polenske adalah jml mg KOH u/menetralkan as.lemak yg tdk larut (yg bukan atsiri dlm destilasi uap) dr 5 gr lemak

28. REAKSI KIMIA & SIFAT KHAS LEMAK d. Bil.Iodium (ukuran derajat ketidakjenuhan) - jml gr iodium yg diserap o/ 100 gr lemak (tiap ik.ganda dlm lemak dpt mengambil 2 atom iodium) e. Uji ketengikan (ukuran derajat ketengikan) - Bil Peroksida (dg KI) - Uji As.Tiobarbiturat - Uji Oven Schaal

29. KETENGIKAN • HIDROLITIK a. Adanya lipase bs menyebabkan reaksi ini, terbentuk as.lemak+gliserol b. nilai gizi tdk terpengaruh • OKSIDATIF a. Trjd krn adanya oksigen b. menurunkan nilai energi dr lemak

35. METABOLISME LEMAK

36. Istilah2 terkaitdenganMetab. Lemak • Lipogenesis • Beta Oksidasi

37. Lipid Metabolism

39. MEMBRAN LIPIDS • Glycerophospholipid • Galactolipid • Sulfolipid • Sphingolipid • sterol

40. Glycerophospholipids(phosphoglycerides), are common constituents of cellular membranes. They have a glycerol backbone. Hydroxyls at C1 & C2 are esterified to fatty acids. Glycerophospholipids An ester forms when a hydroxyl reacts with a carboxylic acid, with loss of H2O.

41. Phospholipids • Phospholipidsconsist of a 3-carbon glycerol linked to a negatively charged phosphate group, and two fatty acids. • Phospholipids are a major component of cell membranes due to their amphipathic nature. • Amphipathic molecules have a nonpolar region (hydrophobic) and a polar region (hydrophilic).

42. Sphingolipids are derivatives of the lipid sphingosine, which has a long hydrocarbon tail, and a polar domain that includes an amino group. Sphingosine may be reversibly phosphorylated to produce the signal molecule sphingosine-1-phosphate. Other derivatives of sphingosine are commonly found as constituents of biological membranes.

43. Sphingomyelin has a phosphocholine or phosphethanolamine head group. Sphingomyelins are common constituent of plasma membranes Sphingomyelin, with a phosphocholine head group, is similar in size and shape to the glycerophospholipid phosphatidyl choline.

44. Palmitate (C16) The energy conversion process of fatty acid --> ATP involves oxidation of fatty acids by sequential degradation of C2 units leading to the generation FADH2, NADH, and acetyl CoA. The subsequent oxidation of these reaction products by the citrate cycle and oxidative phosphorylation generates lots of ATP. -oxidation yields large amounts of ATP 106 ATP - WOW!

45. OXIDATION The -oxidation pathway occurs at the  carbon of the fatty acid, thereby releasing the C-1 carboxyl carbon and  carbon as the acetate component of acetyl CoA. -oxidation reactions HYDRATION OXIDATION THIOLYSIS

46. Palmitoyl-CoA + 7 CoA + 7 FAD + 7 NAD+ + 7 H2O --> 8 acetyl CoA + 7 FADH2 + 7 NADH + 7 H+ -oxidation reactions for palmitate (C16)

47. 31 NADH (31 x ~2.5 ATP) = ~77.5 ATP 15 FADH2 (15 x ~1.5 ATP) = ~22.5 ATP For a grand total = 100 ATP After subtracting the 2 ATP required for fatty acyl CoA activation (AMP --> PPi) And adding the 8 ATP obtained from eight turns of the citrate cycle; The total payout for the complete oxidation of palmitate is 106 ATP ATP currency exchange ratios

48. Besides the payout of ATP that comes from fatty acid oxidation, another benefit is the generation of H2O that occurs when O2 is reduced by the final reaction in the electron transport system, as well as, the formation of H2O in oxidative phosphorylation. • 2 NADH + 2 H+ + O2 --> 2 H2O • 2 FADH2 + O2 --> 2 H2O • ADP + PO42- --> ATP + H2O -oxidation is a chemical source of water for desert animals

49. Ketogenesis When fatty acid oxidation produces more acetyl-CoA than can be combined with OAA to form citrate, then the "extra" acetyl-CoA is converted to acetoacetyl-CoA and ketone bodies, including acetone. Ketogenesis (synthesis of ketone bodies) takes place primarily in the liver.

50. Ketogenesis Acetyl-CoA derived from fatty acid oxidation enters the Citrate Cycle only if carbohydrate metabolism is properly balanced. When fatty acid oxidation produces more acetyl-CoA than can be combined with OAA to form citrate, then the "extra" acetyl-CoA is converted to acetoacetyl-CoA and ketone bodies, including acetone. Ketogenesis (synthesis of ketone bodies) takes place primarily in the liver.