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140 Cards in this Set

  • Front
  • Back
4 main classes of lipids:
1. Fatty acids
2. Steroids
3. Lipid vitamins
4. Terpenes
5 classes of Fatty Acid Lipids:
1. Eicosonaoids
2. GlyceroPhospholipids
3. Triacylglycerols
4. Waxes
5. Sphingolipids
2 categories of Glycerophospholipids:
1. Ether phospholipids

2. Phosphatidates
2 Ether phospholipids:
1. PAF (plt actvtng factor)
2. Plasmalogens
1. Phosphatidyl ethanolamines
2. Phosphatidylserines
3. Phosphatidylcholines
4. Phosphatidylinositols
Sphingolipids are precursor to:
Derivatives of Ceramide:
1. Sphingomyelins
2. Cerebrosides
3. Gangliosides
Lipid is a general term for:
Substances that are Water-insoluble and extractable by polar solvents.
2 main types of constituents make up complex lipids:
1. Fatty acids
2. Isoprene units (5C)
Eicosanoids are derived from:
arachidonic acid
triacylglycerols derive from
fatty acids
ceramides are derived from
how are phospholipids similar to triglycerides?
Both constructed on glycerol backbone
The basic unit of Phospholipids is:
phosphatidic acid
how are phospholipids different from triglycerides?
Phosphatidic acid has phosphate esterified to C3 instead of a fatty acid.
Where do phosphlipids function?
As the major class of membrane lipids
What part of phospholipids mediates their biolog function?
Hydrophilic (phosphate) - affects surface properties of membrane.
What is the important intermediate in phospholipid and triglyceride synthesis?
Phosphatidic acid
Where is phosphatidic acid synthesized? What is unique about synthesis?
-Endopl. reticulum + outer Mito Membrane
-De Novo
How is Phosphatidic Acid formed?
By adding 2 FA onto Glycerol-3-Phosphate
What transfers the FA to glycerol-3-P?
Specific acyltransferases
What is the specificity of Aceyltransferase I and II in making phosphatidic acid?
Acyltransf 1: SATURATED fatty acid attached to C1

Acyltransf 2: UNSATURATED FA attached to C2
Where is Glycerol-3-phosphate coming from in this process?
Dihydroxyacetone Phosphate (DHAP) from glycolysis - reduced
What reduces DHAP to Glycerol-3-P?
Phosphatidates are
Lipid derivatives of phosphatidic acid
4 groups that get added to Phosphatidic acid:
-Choline (these 3 most common)
How are phosphatidates made?
By esterifying the phosphate with one of the polar groups.
What is Phosphatidylcholine?
What is the common feature of Phosphatidyl-ethanolamine/serine and Lecithin (choline)?
-Most abundent lipids in mammalian cell membranes
What are the FA groups at C1 and C2 in phosphatidylinositol?
C1: stearic acid

C2: arachidonic acid
What is important about phosphatidylinositol?
Primary intracellular source of arachidonic acid
How many carbons in:
-Stearic acid
-Arachidonic acid
Stearic = 18

Arachidonic = 20
How many doub bonds in
-Stearic aa
-Arachidonic aa
Stearic = none

Arachidonic = 4 -> (5/8/11/15)
What is the essential molecule needed to form phosphatidate lipids?
REMEMBER THIS UNTIL THE DAY YOU DIE: "Regardless of the pathway used,
The 2nd most important biochemical role of CTP (after Nucleic Acid biosynth) is PHOSPHOLIPID BIOSYNTHESIS"
How is the synthesis of Phosphatidylserine unique?
Takes place by exchange of Serine for PhosphatidylETHANOLAMINE
What are Ether Phospholipids?
Phospholipids with an Ether at the C1 carbon.
Ether phospholipids are synthesized from:
-Long chain FA
-Long chain Fatty alcohols
What adds the ether linkage to a phospholipid?
An enzyme in peroxisomes
2 Types of Ether Phospholipids:
-PAF (pltlet activating factor)
What is PAF's function?
-inflammatory responses
-anaphylactic shock
Where is PAF synthesized and released from?
PMNs - neutrophils
What is the biochemical point of interest about PAF?
-Acetyl replaces FA at C2
What is the effect of replacing the C2 FA with Acetyl?
Increased solubility and ability to function in aqueous environmt
Polar group in PAF is usually:
How are Plasmalogens different from PAF, structurally?
The ether at C1 is a,B-unsaturated.
Location/type of enzyme that makes Plasmalogens?
In the ER - mixed function oxidase
What are Ether-linked lipids associated with (in high amts)?
Invasive ability of metastatic cancer cells - exhibit these lipids in plasma membranes.
What tissues have large amts of:
-Ethanolamine plasmalogen

-Choline plasmalogen
Ethanolamine = myelin

Choline = cardiac
So main difference between PAF and Plasmalogens:
Ether group on Plasmalogens has a double bond in it (just adjacent to the ether bond.
What are Phospholipases?
Family of enzymes that specifically cleave phospholipids
What do Phospholipases do?
Remodel phospholipids for intracellular signalling
4 Types of Phospholipase that I should know:
Phospholipase A1
Phospholipase A2
Phospholipase C
Phospholipase D
Phospholipase A1
Removes FA at C1
Phospholipase A2
Removes FA at C2
Purpose of A1/A2's action:
allow the FA to change to something else
Phospholipase C
Cleave C3 phosphodiester to make Diacylglycerol (leaves an O on C3 but takes PO3 off)
Phospholipase D
Cleave C3 phosphodiester to make
Phosphatidic acid (leaves PO3 on C3 and takes an O off)
Products of cleaving PIP2 (phosphatidylinositol 4,5-bisphosphate) by phospholipase C:
-DAG (diacylglycerol)
-IP3 (Inositol 1,4,5-triphosphate)
What are DAG and PI3
important intracellular signals
So PIP2 cleavage produces
Where is PIP2 located and what is its function?
On inner surface of cell membrane; binds signal molecules sent from extracellular signals binding their receptors (ie hormones)
What causes Phospholipase C to cleave PIP2?
Gprotein - the product of signal cascade initiated by hormone binding.
What results from PLC cleavage of PIP2?
-DAG stays in the membrane
-IP3 is soluble - travels to ER to open IP3-gated Ca2+ channels
What can DAG do from its membrane-associated position?
Activate Protein Kinase C - with the help of Ca2+ released by IP3
What is the main function served by phospholipids?
To anchor membrane associated proteins.
Name of phospholipids that anchor extracellular proteins (LPL and Acetocholine Esterase):
GPI - Glycosyl Phosphatidyl Inositol
Key characteristics of GPI:
-GlcN/Man short oligosacc bonded to C-term of protein
-Phosphoethanolamine residue in btwn above 2
How are GPI-linked extracellular proteins released?

By Phospholipase C Cleavage
How are GPI-linked extracellular proteins generally arranged?

In clusters
How do intracellular proteins become attached to the cytosolic side of membranes?
Through specific interaction of long-chain FA's and ISOPRENOIDS
What does Palmitic acid bind?
An internal Cysteine residue
What does Myristic acid bind?
An N-terminal glycine residue
What are Farnesyl and Geranylgeranyl?
Polyisoprene units
What do Farnesyl and Geranylgeranyl bind?
C-terminal Cystein residue
What is the main distinction between Eicosanoids and Phospholipids?
Eicosanoids lack a glycerol backbone
What is the precursor to Eicosanoids?
Arachidonic acid
Structure of Arachidonic acid:
What is the precursor to arachidonic acid?
Linoleic acid
Structure of Linoleic acid:
What are Eicosanoids?
Paracrine hormones - not transported via blood, just act right on cells nearby point of synthesis.
Why are Eicosanoids shortlived?
-Rapid mitochondrial turnover
-Metabolized by B-oxidation in Peroxisomes
3 classes of Eicosanoids:
1. Prostaglandins
2. Thromboxanes
3. Leukotrienes
2 Pathways for Eicosanoid synthesis:
1. Cyclooxygenase
2. Lipoygenase
How is Arachidonic acid available for Eicosanoid synthesis?
It is part of the structure of Phosphatidylinositol - at C2; This phosphatidate is in membranes
What releases Arachidonic acid from Phosphatidylinositol?
Phospholipase A2
What enzymes make Leukotrienes?
What is the central enzyme in the Cyclooxygenase Pathway?
PGS - Prostaglandin Synthase
What enzyme makes Prostaglandin from Arachidonate?
PGH2 - Prostaglandin H2
So what pathway is used to make:
-Prostaglandins and Thromboxane?
-Prostaglandins/Thromboxane are made via the Cyclooxygenase path

-Leukotrienes via Lipoxygenase
What 2 enzymes are in Prostaglandin Synthase?
1. Cyclooxygenase
2. Glutathione-dependent peroxidase
What is Prostaglandin Synthase composed of? (2 parts)
1. COX = cyclooxygenase
2. Glutathione-dependent peroxidase (PG Hydroperoxidase)
What is essential for COX to work?
2 molecules of oxygen
What does COX do?
Cyclizes C8-C12 on Arachidonic A to form Prostaglandin G2 (PGG2)
What is the distinct difference between Prostaglandins and other eicosonoids?
The 5-membered ring in what used to be Arachidonate
What step occurs in prostaglandin synthesis after PGG2 is formed? Enzyme?
PG hydroperoxidase forms Prostaglandin H2 (PGH2)
What are the 2 isoforms of PGS (Prostaglandin Synthase)? Where are they located?
#1. Constitutive - in most tissues and cells.
#2. Inducible - limited sites
How do the prostaglandin derivatives differ?
By functional groups attached to the 5-membered ring.
So what is the intermediate precursor to all prostaglandins?
What are the 2 key structural differences between prostaglandins and leukotrienes?
1. PG's have reduced double bonds; Leukotr. retain same #.
2. PG's have a 5-C ring; Leukotrienes don't.
What do Prostaglands do in general?
Stimulate uterine smooth muscle contraction, increase body temp, induce inflammation/pain.
What does PGI2 (prostacyclin) do specifically?
Prevents clotting
What opposes Prostacyclin?
PGE2 - Promotes clotting
How are Thromboxanes made?
By converting cyclopentane into a 6 membered oxane ring.
What is the function of Thromboxane?
Blood clotting/reduced blood flow to clot site.
What is different about oxygen requirements for leukotriene vs. prostaglandin synthesis?
Prostaglandin - 2 molecules O2

Leukotrienes - 1 molecule O2
What cells have PGS2 (synthase)?
Macrophages and monocytes
When is PGS2 expressed?
Only when certain agents stimulate it - PAF (Plt activator - Ether phospholipid)
So the effect of PGS2 is:
elevated levels of prostaglandins, so inflammation.
What is the mechanism of Corticosteroids?
Inhibit phospholipase A2 which reduces arachidonic acid production.
What is the effect of Corticosteroids?
How do NSAIDS work?
By inhibiting the COX activity of PGS; arachidonate is available, but not put to use.
What is the most effective NSAID and why?
Aspirin - covalently acetylates COX and blocks its active site.
By what pathway are leukotrienes synthesized?
Lipoxygenase pathway
What is the precursor of leukotrienes?
Arachidonic acid - its the precursor of all eicosanoids.
Lipoxygenase catalyzes the ____ of arachidonate, where Cyclooxygenase (COX) catalyzes the ____ of it.
Monooxygenation instead of dioxygenation
What member of the lipoxygenase family is most important in humans?
Which double bond in Arachidonate is 5-LO spcf for?
What molecule is formed by monooxygenating the C5 double bond of arachidonate?
(think friend)
under what conditions is 5-HPETE produced?
When human tissues/cells undergo inflammatory processes.
What is formed by the loss of water from 5-HPETE?
Leukotriene A4 (LTA4) - an epoxide
What is the 4 in LTA4 referring to?
The # of double bonds - 4
How is LTA4 converted to LTB4?
By adding water to the C11-12 double bond - breaks apart the epoxide and leaves 2 -OH groups
How is LTA4 converted to LTC4?
GSH (reduced) adds to C6, cleaving the epoxide
How is LTD4 formed?
By loss of glutamate from LTC4
How is LTE4 formed?
By loss of glycine from LTD4
What is the unusual characteristic of GSH that is important to remember?
Unusual linkage between Glu-Cys-Gly
What are LIPOXINS?
Products of multiple lipoxygenase pathways; have OH groups attached to C5 and C6
What are the characteristic activities of lipoxins?
Inhibit leukotrienes - anti-inflammatory
What is the other alternative fate of 5-HPETE (versus leukotriene synth)?
5-HETE - more stable than 5-HPETE
How does 5-HETE form?
The C5-OOH redues to C5-OH - either spontaneously or by a peroxidase catalyst.
Prostaglandins exert their effect by paracrine signalling, where Leukotrienes do it by
Receptor-ligand interaction
What type of disorders are associated with elevated leukotrienes?
Inflammation and Hypersensitivity reactions (asthma/anaphylactic shock)
What protein is 5-LO dependent on?
FLAP - 5 lipoxygenase activating protein
What is FLAP?
An integral nuclear membrane protein - binds Arachidonate, allows it to interact w/ 5-LO
What is the function of LTB4?
Chemotaxis - attracts PMNs to combat infection.
What 'term' describes the group functionality of LTC4/LTD4/LTE4?
Slow-reacting substances of anaphylaxis (SRS-A)
What are the effects of SRS-A, and in whom are they seen?
In ppl w/ hypersensitivity
Mechanism of asthma drugs Singulair and Accolate:
Blocks binding of leukotrienes to lung smooth muscle cell receptor.