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CHEM 3303.02 Biochemistry Chapter 10: Lipids

CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments Storage

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Page 1: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage

CHEM 3303.02 Biochemistry

Chapter 10:Lipids

Page 2: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage

Knowledge/ skillsEntire chapter- All except for most of

Lipids as signals, cofactors and pigments

Storage lipids Structural lipids in membranes Vitamins A and D are hormone precursors Vitamins E and K and the lipid quinones are

oxidation/reduction cofactors

Page 3: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage

General information Insoluble in water Principal energy storage ( fats and oils) Phospholipids and sterols are structural

elements of biological membranes Other as cofactors, electron carriers, light

absorbing pigments, hydrophobic anchors for proteins

Chaperones for membrane folding Emulsifying agents in digestion Many lipids play a passive role for energy

storage or as a barrier, some are active and play a role as messengers or signalling molecules such as hormones

Page 4: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage

Storage lipids Fatty acids-

Complete oxidation to CO2 and H2O Carboxylic acids with hydrocarbon

chains ranging from 4-36 carbons Chain can be branched/unbranched Chain can be saturated/ unsaturated May contain ring structures

Page 5: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage

naming Simplified

Chain length:number of double bonds Double bond position given by a Δ followed by

the number of the carbon which is participating in the double bond. Note that the carboxyl group carbon is C-1

E.g. 20:3(Δ3,9,12) denotes a carboxylic acid with 20 carbons and 3 double bonds between C-3 and C4; C-9 and C-10; C-12 and C-13

Most commonly occurring have even numbers with unbranched chains- results from the fact that in biological systems the chains are put together from two Carbon (acetate) units

Page 6: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage

Many double bonds are Δ9, 12,15 in the cis configuration

Almost never see alternating single and double bonds but separated by a methylene group

Trans fatty acids produced by fermentation in diary animals and hydrogenation of fish or vegetable oils- these increase the levels of LDL or bad cholesterol and decrease the levels of HDL or good cholesterol

Page 7: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage
Page 8: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage
Page 9: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage

Physical properties – solubility in water Largely determined by chain length and degree

of saturation of the hydrocarbon chain Longer fatty acyl chain- less soluble Fewer double bonds- less soluble Compare the solubility of lauric acid (12:0,

Mr200) 0.063mg/ml vs glucose (Mr 180) 1,100 mg/ml

Carboxylic acid group is polar and ionized at pH7 and accounts for the slight solubility of the shorter chain fatty acids in water.

Page 10: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage

Physical properties- melting point

Influenced by length and degree of unsaturation of the hydrocarbon chain At room temp the saturated fatty acids from 12:0 to

24:0 are waxy while the corresponding unsaturated fatty acids are oily liquids

Differences due to the degree of packing of the molecules

In fully saturated molecules, large degree of free rotation around the C-C backbone and very flexible and able to pack tightly into nearly crystalline arrays with atoms in contact all along their length

Unsaturated- cis double bond forces a kink in the hydrocarbon chain- result is that cannot pack as tightly as the fully saturated form. Overall van der Waal’s interactions less in unsaturated so less thermal energy to break bonds hence have lower melting points

Page 11: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage
Page 12: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage

In vertebrates, free fatty acids with a free carboxylate group are bound to a protein carrier called serum albumin

Fatty acid derivatives such as esters or amides lack the charged carboxylate group and are less soluble than free fatty acids.

Page 13: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage

Tri acyl glycerols

Composed of fatty acids linked to glycerol- by what linkage?

Page 14: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage

Ester linkage due to formation of a condensation bond

Simple if all acids are the same, e.g. tristerin

Most are mixed

Polar groups of both glycerol and fatty acid are linked so triacylglycerols are nonpolar, hydrophobic and insoluble

Lower specific gravity- float on water

Page 15: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage

Triacylglycerol function Energy storage in adipocytes as fat droplets Oils in plant seeds to provide energy and precursor

molecules for germination The carbon atoms of fatty acids are more reduced than

carbohydrates so that more than twice the energy (gram for gram) is yielded

Because the molecule is hydrophobic, do not need water of hydration associated with polysaccharides (2g per gram of polysaccharide)

Carbohydrates are a quick energy source and are readily soluble in water

Fats are better for long term storage Fats are good insulators against cold temperatures

especially in animals that live in the cold or hibernate Help with maintaining neutral buoyancy in diving

animals like whales

Page 16: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage

There are 4 adipocytes in this picture

Can you tell where they are? Storage lipids can make up more than 80% of the

adipocyte dry cell mass

Page 17: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage

The sperm whale Sperm whale’s head accounts for over 1/3 of its

body weight. About 90% made up of spermaceti organ that is filled with spermaceti oil. The oil helps the animal maintain neutral buoyancy at ocean depths where it hunts its food and is able to change density depending on temperature

Page 18: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage

Saturation of oils Many vegetable oils such as corn and olive oil

are composed of triacylglycerols with unsaturated fatty acids- liquid at room temp

Hydrogenation reduces some double bonds to single bonds and can give trans double bonds

Exposure of lipids to air results in oxidative cleavage of double bonds to produce aldehydes and shorter chain carboxylic acids that are more volatile and smell rancid

Page 19: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage
Page 20: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage

Waxes Esters of long chain (C14 to C36) saturated and

unsaturated fatty acids with long chain alcohols

Melting points (60ºC – 100ºC) Can be used as a metabolic fuel store Provide water repellent properties- help to waterproof Lubricate hair and skin Protect against parasites E.g. lanolin, beeswax, carnuba wax

Page 21: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage
Page 22: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage

Lipid types

This is an important overall picture of the lipids and how they are built

Page 23: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage

Lipids in membranes Membranes serve as a barrier to passage of

polar molecules and ions The molecules are amphipathic, one end is

hydrophobic and the other is hydrophilic The hydrophilic end interact with water on

either side of the membrane- can be a single OH or more complex as in the phospholipids, or sugars as in the glycolipids

The hydrophobic end interact with each other in a bilipid layer structure

Membrane lipids can make up 5 to 10% of the dry mass of cells

Page 24: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage

Glycerophospholipid Aka phosphoglyceraldehydes

Two fatty acids attached via ester linkage to C-1 and C-2 of glycerol

Polar or charged group attached via a phosphodiester linkage to C-3 with an alcohol

Di acyl-glycerol

Page 25: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage

Head group substituents

Page 26: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage
Page 27: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage

Ether lipids Alkyl ether lipid- saturated Plasmalogen- double bond between C-1 and C-2

Page 28: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage

An example of ester and ether linkage Molecular signal to stimulate platelet

aggregation

Page 29: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage

Galactolipids One or two galactose residues connected by

a glycosidic linkage to C-3 of a 1,2 diacylglycerol

Important in plant thylakoid membranes.

Page 30: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage
Page 31: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage

Sulfolipids Sulfonate group bears a negative charge

like a phosphate group

Page 32: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage

Glycerol dialkyl glycerol tetraether

Found in archaebacteria- live in extreme conditions of pH and temperature

Molecule is longer (32C) to make a membrane with a hydrophobic core and hydrophilic ends (glycerol)

Ether bond linkage more stable to hydrolysis than ester bond

Page 33: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage

Sphingolipids Polar head group but use the long chain amino

alcohol sphingosine instead of glycerol Has one long chain fatty acid Has a polar head group linked by a glycosidic

linkage or phosphodiester linkage

Page 34: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage
Page 35: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage
Page 36: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage
Page 37: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage

Breakdown of membrane lipids

Membrane lipids continuously made/broken

Specific enzymes attack each hydrolyzable bond

Defects in these enzymes lead to severe consequences (Tay-Sachs)

Page 38: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage

Diseases associated with problems in breaking down sphingolipids

Page 39: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage

Sterols- e.g cholesterol Have 4 fused Carbon

rings, three 6 carbon and one 5 carbon to form the steroid nucleus- rigid and planar

Present in eukaryotic cells

Cholesterol is ampiphatic

Are precursors for steroid hormones which regulate gene expression

Page 40: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage

Examples of sex hormones

Page 41: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage

Vitamin A, D, E and K Fat soluble vitamins All are isoprenoid compounds synthesized

by condensation of multiple isoprene units Vitamin A and D are hormone precursors

Page 42: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage

1,25-dihydroxycholecalciferol- a hormone that regulates calcium uptake in the intestine and Ca levels in kidney and bone; regulates gene expression to turn on synthesis of Ca 2+ binding protein

Page 43: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage
Page 44: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage

Vitamin A (retinol), hormone and visual pigment

Page 45: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage

Vitamin E- collective name for tocopherols Contain a substituted aromatic ring and long

isoprenoid side chain. Are hydrophobic and associate with

membranes, lipid deposits and lipoproteins Aromatic ring destroys free radicals to protect

fatty acids from being oxidized

Page 46: CHEM 3303.02 Biochemistry Chapter 10: Lipids. Knowledge/ skills Entire chapter- All except for most of Lipids as signals, cofactors and pigments  Storage

Vitamin K Undergoes oxidation and reduction during

active prothrombin formation. Prothrombin splits the peptide bonds in

fibrinogen to fibrin an insoluble protein that holds blood clots together