Biomolecules II: Lipids PDF

Biomolecules II: Lipids For Semester I 2024/2025  at the end of this topic, students should be able to: ❖ identify lipids among the other Topic Learning biomolecules Outcomes ❖differentiate betwe...

Biomolecules II: Lipids For Semester I 2024/2025  at the end of this topic, students should be able to: ❖ identify lipids among the other Topic Learning biomolecules Outcomes ❖differentiate between the major classes of lipids (i.e. fatty acids, triacylglycerols, phospholipids, sphingolipids, wax, isoprenoids, lipoprotein) structurally ❖ relate the structure of the lipids with their role and functions  lipo- or fats not a true polymer, insoluble in water but soluble in non-polar solvents, hydrophobic having various structures & functions What is a general structure → polar hydrophilic head attached to non-polar hydrophobic tail lipid? the head the tail  membrane main components intracellular energy reservoir as an insulator Functions of lipid protects surface special functions → ❖ steroid (hormone) ❖ eicosanoid (signaling molecules) ❖ ganglioside (modulator in cell signal transduction)  ___________ triacylglycerols ____________ Classes of lipids sphingolipids __________ terpenes and steroids _____________  a carboxylic acid with a long hydrocarbon side chain: methyl carboxyl end end Hydrocarbon chain Carboxylic acid group Fatty Acid differ from each other by: ❖ _____________________ ❖ _____________________ ✔ position of double bond in chain modified fatty acids → branched, cyclic exists freely or attached to other molecules  saturated fatty acid → fatty acid with ______ bonds only Types of fatty acid: The degree of unsaturation ❖ linear form ❖ melting point high; exists as solid  unsaturated fatty acid → fatty acid with one or more _______ bonds ❖ types: mono-, di-, tri-, poly- ❖ kink or bend structure ❖ melting point low; exists as liquid  orientation of unsaturated fatty acids  multi structures of fatty acids kink/bend saturated monounsaturated diunsaturated polyunsaturated fatty acid fatty acid fatty acid fatty acid  in addition to saturation, fatty acids are classified as: Types of fatty acid: ❖ ___________ (SCFA) are fatty acids with hydrocarbon chain of < 6C The length of ❖ __________ (MCFA) are fatty acids with hydrocarbon hydrocarbon chain of 6–12 C ❖ ___________ (LCFA) are fatty acids with hydrocarbon chain chain > 12C ❖ ___________________ (VLCFA) are fatty acids with hydrocarbon chain > 22C e.g. of biologically common fatty acids  for a saturated fatty acid: e.g. palmitic acid 16 : 0 total number of carbons the count of double bonds How a fatty acid is abbreviated for an unsaturated fatty acid: e.g. palmitoleic acid 16 :1 c Δ9 the configuration and position of C atom (from –COOH end) where double bonds each double bond starts  for fatty acids that have a long hydrocarbon chain, the last position is labelled ω, the last Greek letter → ω-3 signifies that the first double bond exists as the third carbon-carbon bond from the terminal CH3 end (ω) of the carbon chain e.g. ω-3 18:4 (stearidonic acid) indicates an 18-carbon chain with 4 double bonds, and with the first double bond in the third position from the methyl end double bonds are cis and separated by a single methylene (CH2) group unless otherwise noted  3 fatty acids attached to _________ molecule by a condensation reaction → ester bond neutral fats; hydrophobic functions: ❖ as animal energy reserve → produced more energy per mass Triacylglycerols unit compared to carbohydrates/proteins ❖ provide insulation in low temperature ❖ make fur or feathers water-repellant differ in terms of identity & position of fatty acid residues forms → solid (i.e. fats) or liquid (i.e. oils) Condensation reactions in triacylglycerol formation ester bond  adipose tissues → contain cells made up of fats & oils ❖ can be found at the subcutaneous layer, abdominal space, around main organs ❖ energy reservoir; insulator; protection adipocytes/fats cell → triacylglycerol synthesis & storage; contains fat globules hydrolysed by lipase or alkali (i.e. saponification)  lipid with __________group amphiphilic molecules essential components of membrane, as surface active agent (surfactant) & Phospholipids emulsifying agent  X-group Phospholipid consists of 4 (shown here is choline) main components: ✔ 2 fatty acids attached to C1 1 2 3 and C2 of glycerol ✔ 1 glycerol ✔ _______ group attached to C3 of glycerol ✔ 1 ______ attached to phosphate group  simplest → phosphatidic acid other e.g.: phosphatidylethanolamine; phosphatidylcholine; phosphatidyl serine; phosphatidyl inositol – depends on X group X X group  component of membranes a lipid with a C18 amino alcohol or sphingosine ceramide → a fatty acid joined to sphingosine via an amide bond Sphingolipids fatty acid amide bond  phosphorus-containing phosphorus group sphingolipids; found mainly in attached here cell membranes of brain and nerve cells e.g. sphingomyelin: Types of Sphingolipids: Sphingophospholipid  ceramide with one/more sugar residues in a β-glycosidic linkage at the 1-hydroxyl moiety; sugar residues attached here e.g. ______ & ________ Types of Sphingolipids: galactocerebroside Sphingoglycolipid Galactose Glucose Ceramide N-acetylgalactosamine Galactose N-acetylneuraminic acid ganglioside  esters of long chain weak polar head alcohols with long group chain fatty acids a weakly polar head Waxes grp attached to 2 hydrophobic tails hydrocarbon chains highly insoluble in water → water-repellant character  functions → energy storage; structural components rigidness increased with hydrocarbon chain length & saturation degree e.g.: beeswax, carnauba wax, spermaceti wax  contain repeating isoprene units Terpenes mostly are hydrocarbons but some may contain oxygen can be found in essential oils → e.g. limonene in lemons, citronellal in roses, menthol in peppermint  complex derivatives of triterpenes, squalene consist of __________ rings (A,B,C) & _________membered rings (D) fused together (i.e. cyclopentanoperhydrophenantrene) e.g.: Steroids cholesterol; sterols in plants, fungi & yeast; hormones; bile acids  sterol in animals; principal component of animal cell membrane weakly amphiphilic & Steroids: rigid Cholesterol cholesteryl ester → an ester of cholesterol; between -COO- of fatty acid + -OH of cholesterol  functions of cholesterol: ❖ as steroid hormones precursor 5 families → androgens, estrogens, progestins, glucocorticoids & mineralcorticoids testosteron estrogen ❖ formation of bile acids → produced by liver, stored in gallbladder; aids in lipid digestion; e.g. cholic acid cholic acid  any lipids that is covalently linked to proteins can be found in blood plasma Lipoproteins function is to transport lipids (fats), phospholipids and cholesterol around the body in the blood Density classified according to density: Class Diameter % % % protein % cholesterol (g/mL) (nm) phospholipid triacylglycerol 1.063 HDL 5–15 33 30 29 4 1.019–1.063 LDL 18–28 25 50 21 8 1.006–1.019 IDL 25–50 18 29 22 31 0.95–1.006 VLDL 30–80 10 22 18 50