3. Composition of simple and complex lipids, ketone bodies. biochemically important lipids

composition of simple lipids?

the simplest lipids are fats, oils and waxes

they are esters of fatty acids and alcohols, and does not carry any other group

waxes?

esters of long carbon chain (C>20) monovalent alchols and long chain fatty acids

biological role of waxes?

protecting coating on skin, hair or feather

on fruits and on the leaves of plants to prevent water loss through evaporation

waxes are also used in pharmaceutical, cosmetic and other industries

carnauba wax?

waxes and polishes

food products

pills

beeswax?

used in food, pharmaceuticals and cosmetics

lanolin?

wool-fat used as lotion for eczema

triacylglycerols?

esters of long chain fatty acids and trivalent alcohols

fats: solid triacylglycerols at room temperature, contain mostly saturated fatty acids

oils: liquids at room temperature, contain mostly unsaturated fatty acids. geometry of the double bond is cis

biological functions of TAG?

energy storage

* the carbons of fatty acids are more reduced than those in carbs, therefore oxidation of FA yields 2x the energy, gram for gram

mechanical protection and insulation

glycerophospholipids?

esters of glycerol w. fatty acids and phosphoric acid, in which the phosphoric acid is also esterified by an other alcohol

biological functions of glycerophospholipids ?

building blocks of the cell membrane

certain phospholipids functions as signalling molecules

cephalin (phosphatidyl ethanolamine)?

main constituents of cell membranes

facilitates incorporation of proteins into the cell membrane

Lecithin (phosphatidylcholine)?

main constituents of cell membranes

occurs in high quantities in egg yolk and soya beans

in signal transmission

precursor of DAG

Phosphatidylserine?

constituents of cell membranes

it occurs in higher amount in myelin

it is the cofactor for PKC, has a role in blood coagulation and programmed cell death

can act as both a base and an acid

Phosphatidylinositol?

a constituent of cell membranes

very abundant in brain

main source of arachidonic acid

in signal transmission: gives diacylglycerols

cardiolipin (bisphosphatidylglycerol)?

two phosphatidic acids are linked through a glycerol

occurs in the inner mitochondrial membrane

necessary for proper function of the enzymes of the resp. chain

glycerophosphospholipids in signal transmission?

sphingolipids?

amides of FA and sphingosine which is linked to other polar groups

the fatty acid:

* saturated or contains 1 double bond, can have odd or even number of carbons, generally
* can contain OH group
* multisaturated FAs are rare in sphingolipids

backbone is not glycerol

the backbone is a long-chain amino alcohol

a fatty acid is joined to sphingosine via amide linkage

a polar head group is attached w. glycosidic or phosphodiester linkage

sugar containing sphingolipids occur mostly on the outer surface of plasma membranes

biological functions of sphingolipids?

the main constituent of the outer layer of the cell membranes

they occur mainly in nervous tissue, they have an important role in recognition

ceramides?

R-carbon chain of fatty acid

precursor of other sphingolipids

sphingomyeline?

the most abundant sphingolipid

occurs in lipid rafts

* lipid raft: 10-200nm, heterogenous, ordered structures in the membrane

classes of sphingolipids?

neutral glycophospholipids

sulphated glycolipids

gangliosides

neutral glycophospholipids?

the carbohydrate part doesn’t contain negatively charged groups

most frequent monosaccharides are:

* glucose
* galactose
* N-acetulglucosamine
* N-acetyl galactosamine

examples are:

* cerebrosides
* globosides

cerebrosides?

monoglycosyl ceramides

constituent of myelin in CNS, and lipid rafts

globosides?

ceramides of di- or oligosaccharides

e.g. blood type antigens

sulphated glycolipids?

galactocerebrosides, in which the 3rd OH-group of galactose is esterified by sulphuric acid

constituent of myelin

gangliosides?

the carbohydrate part is an oligosaccharide, which contains a negatively charges sialic (N-acetylneuraminic) acid moiety

occur in grey matter of brain

cell type specfic antigens, receptor

eicosanoids?

carboxylic acids of 20 carbons

enzymatic conversion of arachidonic acid yields:

* cyclooxygenase: prostaglandins, thromboxanes
* lipoxygenase: leukotrienes

biological role of eicosanoids?

paracrine hormones

mediators in healthy and pathological cells (reg. of blood pressure, clotting, contr. of smooth m.)

overproduction of prostaglandins → fever, inflammation, nausea, vomiting

prostaglandins?

20-C long carboxylic acid w. substituted cyclopentane ring

PGE and PGI2

PGE?

stimulates contraction of smooth miscles in uterus

protects epithelium from gastric juice and reduce acid secretion

PGI2?

inhibits aggregation of thrombocytes

vasodilator

Biosynthesis of prostaglandins?

oxidation and cyclisation by cycloxygenase

reduction to 15-OH by peroxidase

thromboxanes?

produced by thrombocytes to initiate blood clotting

TXA2: induces aggregation of thrombocytes and is a vasoconstrictor

Leukotrienes?

they are produced in granulocytes and mast cells

mediators of inflammation and allergic reactions

terpenoids?

built from isoprene units

biological role:

* precursor of steroids and caratenoids
* hormones and vision
* anti-oxidants
* essential oils

ketone bodies?

3 types of ketone bodies, where two can be utilized by our body for energy

* acetone
* acetoacetate
* β-hydroxybutyrate