Biomolecules Lipid

8/11/2019 Biomolecules Lipid

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Lipids


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LIPIDSA broad group of naturally occurring molecules which

includes fats, waxes, sterols, fat-soluble vitamins,monoglycerides, diglycerides, phospholipids andothers.

Function as energy storage, as structural componentsof cell membranes and as important signaling

molecules.


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Classes of LipidsAll biological lipids are amphipathic (contain

polar and nonpolar in structure)

Fatty acidsTriacylglycerols

Phospholipids

SphingolipidsWaxes

Isoprene-based lipids (including steroids)


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Lipids Open chain:

long nonpolar tail with a polar head

OH

Oeg. A fatty acid


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1. Fatty acids Monocarboxyc acids contain HC chains of variable

lengths (12-20 C)

Important components of several types of lipidmolecules

Saturated (C-C) chains pack tightly and form morerigid, organized aggregates (i.e., membranes)

Unsaturated (C-C, C=C or more) chains bend and packin a less ordered way, with greater potential for motion


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Saturated Fatty acidsKnow the common names and structures for fatty

acids up to 20 carbons long

Saturated

Lauric acid

Myristic acid

Palmitic acid Stearic acid

Arachidic acid


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Saturated Fatty Acids

Lauric acid: a typical saturated fatty acidwith 12 carbons

in the chain(in salt form) Fatty acid: 12-20 carbons, even # carbons, no branching,

nonpolar carbon chain, polar COO-group (as anion).

CH3

CH2CH

2

CH2CH

2

CH2CH

2

CH2CH

2

CH2CH

2

C

O

O

Nonpolar hydrophobic tail

Polar hydrophilic head


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Unsaturated Fatty acids Palmitoleic acid (16:1) Oleic acid (18:1)

Linoleic acid (18:2)

-Linolenic acid (18:3)

-Linolenic acid (18:3)

Arachidonic acid (20:4)


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Unsaturated Fatty Acids The first double bond is usually at the ninth carbon. The

double bonds are not conjugated and are usuallycis.

CO

OCH

2CH2

C C

CH2

CH2

CH2

CH2

CH2

CH2

HH

CH2

CH2

CH2

CH2

CH3

Palmitoleic acid, salt form

Cis double bond results

in a bent chain and lower mp.


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2. TriacylglycerolsAlso called triglycerides

Esters of glycerol with three FA

No charge-neutral fatsA major energy source for many organisms

Why?

Most reduced form of carbon in nature

No solvation needed

Efficient packing


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TriacylglycerolsWhen all three alcohol groups of

glycerol form esters with fatty acids, atriacylglycerol (triglyceride) is formed.

CH2

CH

CH2

O

O

O C

O

CO

C

OR1

R2

R3


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Triacylglycerols

TAGs which are solids at room temperature are richin saturated acids and are called

TAGs which are liquids at room temperature arerich in unsaturated acids and are called

e.g. oil seeds include peanut, corn, safflower, palm, andsoybean.


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Triacylglycerols

Triacylglycerols store fatty acids as fats in animal bodies.

Fat provide insulation in low temperature (poorconductor of heat)

Before a fat can be oxidized, it must be hydrolyzed to the

Biologically this is done by lipases. Chemically base hydrolysis is called saponification.


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3. Phospholipids

Have hydrophobic and hydrophilic domains.

Structural components of membranes

Emulsifying agents

Suspended in water they spontaneously rearrange intoordered structures

Hydrophobic group to center

Hydrophilic group to water (Basis of membrane structure)


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Phospholipid molecules in aqueous

solution


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Glycerophospholipids

Essential components of cell membranes and arefound in small concentrations in other part of cells

Neural tissue (including brain) contain high amounts

of glycerophospholipids Involved in metabolism and cell signaling.


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Glycerophospholipids Examples:

Phosphatidyl(choline)

Phosphatidyl(ethanolamine)

Phosphatidyl(serine)

found in biological membranes


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4. SphingolipidsA class of lipids containing a backbone of sphingoid

bases, a set of aliphatic amino alcohols that includesphingosine.

Discovered in brain extracts in 1870

Play important roles in signal tranmission and cellrecognition.


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Sphingolipids These lipids are based on _____________, are found in plants

and animals, and are common in the nervous system.

CH CH CH2 CH3

CH OH

CH NH2

CH2OH

12


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TYPES OF SPHINGOLIPIDSCeramides:

Produce in mammalian cells and in plants

Most simple sphingolipids The other sphingolipids are derivaties of ceramides

such as glycolipids.

Glycolipids are large group of sphingolipids because

they contain one or more molecules of sugar.


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Glycolipids

are lipidswith a carbohydrateattached. Their role is to

provide energyand also serve as markersfor cellularrecognition

Frequently a glucose or galactose is bound to theprimary alcohol of a ceramide. The compound is called

a cerebroside. The carbohydrates are found on the outer surface of all

eukaryoticcell membranes.

They extend from the phospholipid bilayer into the

aqueous environment outside the cell where it acts as arecognition site for specific chemicals as well as helpingto maintain the stability of the membrane and attachingcells to one another to form tissues.
http://en.wikipedia.org/wiki/Lipidshttp://en.wikipedia.org/wiki/Carbohydratehttp://en.wikipedia.org/wiki/Energyhttp://en.wikipedia.org/wiki/Genetic_markerhttp://en.wikipedia.org/wiki/Cell_(biology)http://en.wikipedia.org/wiki/Eukaryotichttp://en.wikipedia.org/wiki/Biological_tissuehttp://en.wikipedia.org/wiki/Biological_tissuehttp://en.wikipedia.org/wiki/Eukaryotichttp://en.wikipedia.org/wiki/Cell_(biology)http://en.wikipedia.org/wiki/Genetic_markerhttp://en.wikipedia.org/wiki/Energyhttp://en.wikipedia.org/wiki/Carbohydratehttp://en.wikipedia.org/wiki/Lipids


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The carbohydrate structure of the glycolipid is

controlled by the glycosyltransferases that add thelipids and glycosylhydrolases that modify the glycanafter addition.

Sphingolipidosescan be associated with defects in

metabolism.

l l
http://en.wikipedia.org/wiki/Sphingolipidoseshttp://en.wikipedia.org/wiki/Sphingolipidoses


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Glycolipids

O

CH2OH

HH

OHH

OH

OH

HH

OCH CH CH2 CH3CH

OHCHNH

CH2 12

C O

R1 A cerebroside


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5. Waxes

Esters of long-chain alcohols with long-chain fatty acids

Highly insolubleAnimal skin and fur are wax-coated

Leaves of many plantsBird feathers


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Wax EstersWaxes are typically esters of fatty acids and fatty

alcohols. They protect the skin of plants and fur of

animal

Examples of waxes include carnuba, from the leavesof the Brasilian wax palm, and beeswax.


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6. Isoprenoids The five-carbon unit that constitutes the basic building block

of isoprenoids is a hydrocarboncalled isoprene

CH2C

CH3

CH CH2CH

2C

CH3

CH2CH

2O P

O

OP

O

O

OOisoprene unit isopentenyl-pyrophosphate
http://www.britannica.com/EBchecked/topic/278321/hydrocarbonhttp://www.britannica.com/EBchecked/topic/296480/isoprenehttp://www.britannica.com/EBchecked/topic/296480/isoprenehttp://www.britannica.com/EBchecked/topic/278321/hydrocarbon


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Isoprenoids two or more units of hydrocarbons, with each unit

consisting of five carbonatoms arranged in a specificpattern

Plant terpenoids used for their aromatic qualities

Play role in traditional herbs remedies and underinvestigations for antibacterial, antineoplastic and

pharmaceutical functions. pigmentsand fragrances tovitaminsand precursors of

sex hormones
http://www.britannica.com/EBchecked/topic/278321/hydrocarbonhttp://www.britannica.com/EBchecked/topic/94732/carbon-Chttp://www.britannica.com/EBchecked/topic/460189/pigmenthttp://www.britannica.com/EBchecked/topic/630930/vitaminhttp://www.britannica.com/EBchecked/topic/536988/sex-hormonehttp://www.britannica.com/EBchecked/topic/536988/sex-hormonehttp://www.britannica.com/EBchecked/topic/630930/vitaminhttp://www.britannica.com/EBchecked/topic/460189/pigmenthttp://www.britannica.com/EBchecked/topic/94732/carbon-Chttp://www.britannica.com/EBchecked/topic/278321/hydrocarbon


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Terpenes

Large and diverse class of organiccompounds produced by variety of plants,particularly connifer

Major components of resin

Roles as end products in many organism,major biosynthetic building blocks withinnearly every living creature.

When modifies chemically, such as byoxidation or rearrangement carbonskeleton - isoprenes


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Terpenes

OH geraniol

farnesene

phytol

-carotene

OH


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Steroids Found in plants, animals and fungi.

Made in cell either from the sterol lanosterol (animalsand fungi) or from cycloartenol (plants).

Steroid hormones serve many functions in animals -

including salt balance, metabolic function and sexualfunction


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Steroids Steroid lipids are based on the ring system shown below.

1

2

3

4

56

7

8

910

11

1213

14 15

16

17

A B

C D

St id E l


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Steroid Examples

CH CH2

CH2

CH2

CH(CH3

)2

OH

H

CH3 H

CH3

H

H

H

CH3

Cholesterol

O

CH3

CH3

OH

testosteroneCH3

CH3

C

CH3

O

progesterone

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