2.05 Lipids Flashcards
Physical (rather than chemical) properties common to all lipids
Insoluble in water
Soluble in nonpolar solvents
Groups of compounds related by certain physical properties
Lipids
Generally compartmentalized to protect themselves from watery environment of cells
Lipids
Functions of lipids
Major source of energy (triglycerides)
Provide hydrophobic barrier in cell membrane (phospholipid)
Coenzyme and regulators
Hormones (cholesterol, steroids)
Mediators of inflammation (prostaglandin, leukotriene)
Electrical insulators in myelinated nerves (sphingomyelin)
Classification of lipids
Simple
Complex
Derived Lipids
Fats/oils: esters of FA with alcohol
Waxes: esters of FA with higher MW monohydric alcohol
simple lipids
Phospholipids: FA + alochol + phosphoric acid residue
Glycolipids: FA + spingosine + carbohydrate
Sulfolipids, amino lipids,
complex lipids
Hormones, Ketone bodies, glycerol
Derived lipids
Long chains of carboxylic acids
Classified according to degree of saturation
Fatty acids
No double bond
Saturated FA
One double bond
Monounsaturated FA
More than one double bonds
Polysaturated FA
Most frequently used system
Unsystematic, conscise and often unambiguous
Trivial nomenclature
Mainly named after number of hydrocarbons
Technically clear
IUPAC
Systematic names
Double-bond indicated by delta x
Delta x nomenclature
Double bond located from the xth carbon-carbon bond starting from the terminal methyl carbon towards the carbonyl carbon
n-x Nomenclature
In the from C:D where C is the number of carbon atoms in the FA, and D is the number of double bonds
Lipid numbers
16:0
Palmitic acid
18:2; 9,12
Linoleic acid
18:3; 9,12,15
Linolenic acid
20:4; 5,8,11,14
Arachidonic acid
omega 3
Linolenic acid
omega 6
Linoleic acid
Linoleic acid and Linolenic acid are considered _____
Essential FA
Most common FA
Palmitic acid
Eicosanoids are derived
Arachidonic acid
Major end product of CHO fermentation by rumen organisms
Acetic acid
In certain fats in small amounts
An end product of CHO fermentation by rumen organisms
Butyric, valeric, caproic
Spermaceti, cinnamon, palm kernel, coconut oils, laurel, butter
Lauric acid
Nutmeg, palm kernel, coconut oils, myrtles, butter
Myristic acid
Common in all animal and plant fats
Palmitic acid, stearic acid
Geometric isomerism of unsaturated fatty acids
Cis
Trans fatty acid
Hydrocarbons are on the same side of the double bond
Cis FA
Hydrocarbons are on the opposite side of the double bond
trans
Being more liquid at room temperature
Fluidity
Temperature where solids change to liquids
Melting point
Relationship of fluidity and melting point
Inversely proportional
Increase chain length: fluidity ___, MP ____
Decreases; Increases
Decrease saturation; fluidity ____, MP ____
Increases; Decreases
Precursor of arachidonic acid
Linoleic acid
Deficiency of this essential FA results in decreased vision and altered learning behavior
Linolenic acid
Lowers thromboxane production
Reduced tendency of platelets to aggreagate
Omega fatty acids
Esters of the trihydric alcohol glycerol and fatty acids
Main storage forms of energy in the body
Triglycerides
Extremely potent compounds that elicit a wide range of responses, both physiologic and pathologic
Eicosanoids
Comprise prostaglandins, thromboxanes, leukotrienes and lipoxins
Eicosanoids
Dietary precursor of the eicosanoids
Linolenic acid
Immediate precursor of the eicosanoids
Released from membrane lipids by phospholipase A2
Arachidonic acid
Synthesized in platelets and cause vasocontriction and platelet aggregation
Thromboxane (TXA2)
Produced by blood vessel walls and are potent inhibitors of platelet aggregation
Prostacyclin (PGI2)
Mixture of leukotrienes C4, D4, E4
Potent constrictors of broncial airway musculature
Slow-reacting substances of anaphylaxis (SRS-A)
From arachidonic acid -> cyclooxygenase pathway
Prostaglandin
Thromboxane
From arachidonic acid -> lipoxygenase pathway
Leukotrienes
Amphipathic compounds composed of alcohol, diacylglycerol or sphingosine, phosphodiester bond
Phospholipid
Predominant lipids of cell membranes
Degraded by phospholipases
Phospholipid
Most abundant phospholipid
Found in cell membranes
Phosphatidylcholine
Lecithin
Ehanolamine replaces choline
Also found in cell membranes
Phosphatidylethanolamine
Cephalin
Serine replaces choline
Found in most tissues, cell membrane
Plays a role in apoptosis
Phosphatidylserine
Active lipid component of lung surfactant
Inadequate levels lead to Newborn Respiratory Distress Syndrome
Decreases the surface tension of alveoli, enabling them to expand again
Dipalmitoylphosphatidylcholine
Dipalmitoyllecithin
DPPC
3 phospholipids in cell membrane
Phosphatidylcholine
Phosphatidylethanolamine
Phosphatidylserine
Reservoir for arachidonic acid in the cell membranes
Source of 2nd messengers
Phospatidylinositol 4,5 BP
Degraded by phospholipase C to produce inositol triphosphate and diacylglycerol
IP3 and DAG mediate the release of intracellular calcium and activation of protein kinase C
Phospatidylinositol 4,5 bisphosphate
2 molecules of phosphatidic acid esterified through their phosphate groups to an additional molecule of glycerol
Found only in the mitochondria and is essential for its proper function
Only non-protein substance that is considered as antigen
Cardiolipin
Part of the glycocalyx located on the outer layer of the cell membrane and functions in cell recognition and cell adhesion
Found in high concentrations in nervous tissue
Glycolipid
Sphingosine + fatty acid
Ceramide
Ceramide + glucose/galactose
Cerebroside
Ceramide + oligosaccharide
Globoside
Ceramide + N-acetylneuramic acid
Ganglioside
Ceramide + sulfated galactose
Sulfatide
Major glycoshingolipid of the brain and the nervous tissue
Can be converted to sulfogalatosylceramide
Galactosylceramide
Present in nervous tissue
Parts of receptors
Ganglioside
Receptor in the human intestine of cholera toxin
GM1
Only significant sphingophospholipid in humans where it is an important constituent of the myelin sheath of nerves
Sphingomyelin
Similar cyclic nucleus resembling phenanthrene to which cyclopentane ring is attached (4 rings)
Methyl side chains at position 10, 13, and a side chain usually at position 17
Steroid
More common and more stable form
chair form
Best known steroid
Very hydrophobic compound composed of 4 fused hydrocarbon rings and 8-membered branched hydrocarbon chain
Cholesterol
Cholesterol has a single hydroxyl group located at _____ of the __ ring to which a FA can be attached to form _____
C-3; A; Cholesteryl ester
Cholesterol is the precursor of ______
Cell membrane
Vitamin D
Adrenocortical Hormones, Sex Hormones
Bile Acids
Active form of vitamin D
1,25-dihydroxycholecalciferol
Two primary bile acids
Cholic acid, chenodeoxycholic acid
Peroxidation of lipids exposed to oxygen produces ____
Highly-charged, unstable oxygen molecules with an unpaired electron
Oxygen free radicals
Peroxidation of lipids is triggered by _____
Existing free radical
Light
Metal ions
Peroxidation of lipids is catalyzed by _____
Heme compounds
Leukotrienes
Oxygen free radicals are counteracted by ____
Anti-oxidants
Auto-oxidation
Peroxidation
Types of Antioxidants
Preventive antioxidants
Chain-breaking antioxidants
Include catalase and glutathione peroxidase that reacts with ROOH, selenium, chelators
Preventive antioxidants
Activates glutathione peroxidase
Selenium
Chelators of metal ions
EDTA and DTPA
Include superoxide dismutase (SOD) and vitamin E
Chain-breaking antioxidant
Partly hydrophilic, party hydrophobic
Amphipathic lipids
Examples of amphipathic lipids
FA, phospholipids, sphingolipids, bile salts
Nomenclature
The carbon atoms are numbered, beginning with the _____ as carbon 1
Carbonyl carbon
Two classes of phospholipids
Glycerophospholipids (those that contain glycerol)
Sphingophospholipids (those that contain sphingosine)
Simplest phosphoglyceride and the precursor of the other members of the glycerophospholipids
Phosphatidic acid
A long chain fatty acid is attached to the amino group of sphingosine though an amide linkage, producing a ______
Ceramide
Alcohol group at C-1 of sphingosine is esterified to phosphorylcholine, producing ______
Sphingomyelin
Structural component of all cell membranes, modulating their fluidity and, in specialized tissues, precursor of hormones
Cholesterol
Ring A of cholesterol has a hydroxyl group at ___
Carbon-3
Branched hydrocarbon chain of cholesterol is attached to ____ of the D ring
Carbon-17
Ring B has a double bond between ____
C-5 and C-6