Chok Biochem 1st Shift Reviewer Fatty Acid

8/9/2019 Chok Biochem 1st Shift Reviewer Fatty Acid

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CHEMISTRY OF LIPIDS

- naturally occurring, non-polar, soluble in non-polar organic solvents- membrane component, energy storage, precursors, insulation, lipoproteins, appetite stimulant

CLASSIFICATION OF LIPIDS

I. Simple – esters of fatty acids (FA) and alcohols

A. Triglycerides, neutral fats

B. WaxesII. Compound

A. Phospolipds (Phosphatides)B. SphingolipidsC. Glycolipids

III. DerivedA. Terpenoids and SteroidsB. Sterols

1. Cholesterol2. Ergosterol3. 7-dehydrocholesterol4. androgens and estrogen5. adrenal corticosteroidsC. Fatty Acids

FATTY ACIDS (FA)

- monocarboxylic acids containing linear hydrocarbon chains with an even number of C, usually C12-C20

o C1 = carboxylated, C2 = α, C3 = β, ω C = methylated

- may be unsaturated (double bonds (DB)), almost always at C18-C20, usually in cis config

- Non-conjugated DB System: DB interrupted by a methylene group (-CH2-), pentadiene

- Conjugated DB System:

- C-C and C-H bonds non-polar (hydrophobic) character even with the COOH group (hydrophilic)= amphipathic

- Naturally occurring satFA that have 1-8 atoms are liquid; more C = solid

- Free FA are few in nature, at physio pH = FA are ionized

- Physical Properties

o ↑ chain length = ↑ Boiling point (BP) and melting point (MP)

o ↑ unsaturation = ↓ MP (due to structure of unsaturated FA: kinks)

o ↑ chain length = ↓ solubility

- Nomenclature

o Delta system: Cx:yΔz



y

Cleaves sn-1 and sn-3: diacylglycerol + 1 FA monoacylglycerol +2 FA glycerol + 3FA)

o Transesterification: rearrangement of acyl groups; modifies physical and nutritional properties

Hydrolysis to remove Esterification to reattach

Olestra: non absorbable cooking oil; sucrose core + 6-8 FA chains

o Hydrogenation – producing oleomargarine and shortening

Unnatural trans-fats associated with ↑ heart disease, cancer, diabetes, obesity, immune, reproductiveresponses

Significantly ↑ LDL, ↓ HDL

o Slow Hydrolysis of Fat: yields FFA and oxidation of DB producing peroxides causing rancidity of fats

- Waxes: neutral fats; ester of long chain FA and ↑ molecular weight (MW) alcohols (C14-34), solid, for coating

o generally mixtures of chain length

o COOH at 16-36 (even #)

o OH at 24-36 (even #)

o Beeswax is 30-C OH and 16-C acid

COMPOUND LIPIDS

- Phospolipids – lipid with phosphate

o Phosphoglyceride / phosphoacylglycerols, glycerol phosphatides – glycerol backbone, ester = diff OH with

phosphatidic acid

α esterified long chain saturated FA, β esterified with unsaturated FA

nonpolar hydrocarbon chain and polar OH end = surface active amphipathic lipids

micelles in water, fails to dissolve

in all tissues, almost entirely in cell membrane

o

Phosphatidic acid – simplest in structure, precursor of other phosphoacylglycerols; FA in α and β, H3PO4 in α’.o Phosphatidylcholines (lecithins) – OH soluble, acetone insoluble, most abundant, 50% of all phosphoacylglycerides,

zwitterions; lung tissue produces 1,2-dipalmitoylphosphatidylcholine as lung surfactant

o Phosphatidylethanolamines and serines (cephalins) – acetone and alcohol insoluble, in brain and nervous tissue,

acidico Phosphatidylinositols (phosphoinositides) – regulatory function of eukaryotic cell

o Plasmogens: either phosphatidal cholines, serines, ethanolamines; long chain α-β unsaturated alkyl ether instead of

FA

Abundant in membranes of nerves and muscles

Hydrolysis

1 mole of long chain aliphatic aldehyde, FA, glycerolphosphate and nitrogenous base

o Cardiolipin – 2 molecules of phosphatidic acid connected by glycerol; in mitochondrial membranes

Phosphoglycerides

Name Group added at – Formula of X Added Info



Side chain @ C17 consists of 5 C terminating with COOH

• Cholic acid – OH @ C7, C12

• Deoxycholic acid – OH @ C12

• Chenodeoxycholic acid – OH @ C7

• Lithocholic acid

o Adenocortical Hormones – C21, produced by adrenal cortex, pituitary secretes ACTH to stimulate adrenal gland to

secrete

Conjugated DB at C3 and C4, unsaturated ketone and OH C11

• corticosterone

• Cortisol (17-hydrocorticosterone)

• Aldosterone

o Sex hormones (androgen) – C19, devoid of C side chain at C17, testosterone

o Female hormones – C18

Estrogen – estradiol has aromatic ring A, acidic OH at C3; estrone, estriol

Progesterone – side chain at C17, pregnanediol in urine

- Prostaglandins – first detected in seminal plasma from prostate gland, in very small quantities

o Contraction of SM, blood pressure, nerve transmission, dev’t of inflammatory process, water retention, electrolyte

imbalance, blood clottingo Prostanoic acid – immediate precursor derived, C20 monocarboxylic acid with internal cyclopentane ring

o 3 major classes of 1° prostaglandins:

A – α, βunsaturated

E – β-hydroxy ketones

F – 1,3-diols

o Subscript numerals refer to number of DB in side chains

- Leukotrienes – produced by leukocytes, has 3 conjugated DB, extremely potent vasoconstrictor of SMo Addition of hydroperoxygroups to arachidonic acid; products of lipogenase = hydroxyperoxyeicosatetraenoic acid

(HPETE)o OOH substituents of arachidoinc acid may occur at C5, 8, 9, 11, 15

5-HPETE – basophils, polymorphonuclear leukocytes, macrophages

12HPETE – platelets, pancreatic endocrine islet cells, glomerular cells

15HPETE – occurs in reticulocytes, eosinophils, T cells

- Pheromones – ↓ MW lipids, volatile



DERIVED LIPIDSName # of C Special Structure Uniqueness / f(x) Found where

Terpenoidsplants as oils, very large, important for rubber,carotenoids, ubiquinone, CoQ, steroids

Terpenes 5n isoprenes / isopentane units

Steroidscycloperhydrophenanthrene sex hormones, emulsifying agents, lipid transporter,

anti-inflammatory agents, metabolism regulation

Cholesterol 27 C4 fused rings A B C D, CH3 @ C10&13,aliphatic hydrocarbon @ C17, DBbetween C5&C6, OH @ C3

Amphipathic, contributes rigidity,1° metabolic precursor

Most abundant sterol

Bile Acids

24 C

Side chain @ C17 has 5C terminates inCOOH @ C24

Assists in lipid digestion Derived from cholesterol

Cholic acid OH @ C7&C12Deoxycholic acid OH @ C12

Chenodeoxycholic acid OH @ C7

Lithocholic acid No addt’l OH

Adenocortical hormones

21 C

Conjugated DB @ C3&C4, unsaturatedketone @ side chain

Adrenal cortex

Corticosterone Parent compoundCortisol (17-hydrocorticosterone)

Unsaturated ketone @ C11 Modifies cortisol

Aldosterone OH @ C11 Water and electrolyte metabolism

Sex hormone / Androgen 19 C DB between C5&C6, No C17 side chain testosteroneFemale hormone

18 C(?)

Estrogen (estradiol)Ring A is aromatic, No C17 side chain,acidic OH @ C3

Progesterone C17 side chain, Pregnandediol in urine

Prostaglandins

contraction of SM, blood pressure,nerve transmission, dev’t of inflammatory process, water retention, electrolyte imbalance,blood clotting

1st detected in seminal plasma, nanograms in mostmammalian tissues,

Prostanoic acid 20 C

Monocarboxylic acid, internalcyclopentane ring,

A – α, βunsaturated

E – β-hydroxy ketones

F – 1,3-diols

Subscript numerals refer tonumber of DB in side chains

Leukotrienes

3 conjugated DB vasodilator Leukocytes, addition on hydroperoxy groups toarachidonic acid

5-HPETE – basophils, PMN,leukocytes, macrophages

12HPETE – platelets,pancreatic endocrine islet cells, glomerular cells

15HPETE – occurs in

reticulocytes, eosinophils, T cells



Pheromones Low molecular weight, volatile

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Chok Biochem 1st Shift Reviewer Fatty Acid