Flashcards in Lecture 5 Lipids Deck (76):
Small hydrophobic or amphiphilic molecules
Extractable by nonpolar solvents (e.g., chloroform:methanol)
Include fats, waxes, sterols, mono/diglycerides, phospholipids, etc.
Originate from ketoacyl and isoprene groups
Simplest form of lipids, found primarily in plasma
-Esterified to glycerol to form triacylglycerol (triglyceride)
solid storage form of lipids, found primarily in adipose tissue (also mono and di forms)
major class of membrane lipids in all cells
(cholesterol) compounds and (glyco)sphingolipids linked with biological membranes
Energy storage, structural elements of cells and organelles, signal transduction.
Triglycerides (fats) degrade to glycerol and free fatty acids in response to hormonal signals
Released into plasma for metabolism primarily in muscle and liver
ex vivo hydrolysis by a strong base (e.g., NaOH)
One of the products, sodium salt of the fatty acid = soap
Structural elements of cells and organelles
Vesicles, liposomes, or membranes (plasma) in aqueous environments
Carboxylic acids with long aliphatic chain. Usually with an even number of carbons, usually unbranched. Saturated or unsaturated. Numbered from carboxyl end.
Common fatty acids
Short, medium, long chain. Essential and non-essential.
2-4 carbon atoms. n = 4, butyric acid
6-10 carbons atoms, n= 8, caprylic acid
between 12 and 26 carbons, n=16 palimitic acid.
Essential and nonessential
Cannot and can be synthed in body. Linoleic and linolenic are two essentials.
Central to carb and fat metabolism.
Single double bond (cis)
Two or more double bonds
Not conjugated, separated by methylene groups
Polyunsaturated FAs are classified into two groups:
ω-3: first double bond appears three carbons from the terminal methyl group
ω-6: first double bond appears six carbons from the terminal methyl group
Physical properties of fatty acids
Physical properties largely determined by the length and degree of unsaturation of the hydrocarbon chain
The longer the fatty acid chain length, the poorer the solubility in water.
Carboxylic acid end is polar, imparting moderate solubility of short-chains (
Fewer double bonds in fatty acid
Lower solubility in water.
Melting point decreases with
number of double bonds - Cis-double bonds place a kink in the linear structure, interfering with close packing, therefore requiring a lower temperature for freezing (i.e., lower melting point; e.g., oils)
Saturated lipids - the most stable arrangement is very close packing of the side chains
Most fatty acid double bonds
Associated with heart disease. Caused by hydrogenation of unsaturated fatty acids. Raises melting point of oils -solid at RT - margarine.
Oils can go bad
oxidations of double bonds can result in cleavage to aldehydes and carboxylic acids
Rancidity of oils
Fatty acids formed in
Liver and adipose tissues, mammary glands during lactation. Unsaturated fatty acids account for 2/3 of all fatty acids in body. Oleate accounts for 1/2 of total
Palmitate (saturated) accounts for about one quarter of total
Fatty acids are rarely found floating free in solution- can be complex.
Carboxylates (salt or ester) no longer bear a negative charge
Very nonpolar - insoluble in water
Advantage - storage fuel instead of polysaccharides. More energy present, more reduced than carbs. nonpolar and not hydrated by water - stored in insoluble fat molecules.
catalyze hydrolysis of ester bonds to glycerol and fatty acids for fuel or other purposes.
Glycerides+sodium hydroxide =
glycerol + fatty acids (soap- salt derivatives)
Forming soap - fatty acids emulsify oils in dirt – allows for removal of oily dirt with water – detergents; micelles, liposomes
Major component of cell membranes. Polar lipids derived from phosphatidic acid. sn-3 position occupied by phosphate esterified to amino compound - choline, serine, etc.
Second largest phospholipid class. Backbone is not glycerol, but sphingosine. Fatty acid is joined to sphingosine via an amide linkage rather than an ester linkage with glycerol
Contain various head groups, including sugars (glycolipids)
Found largely in the outer face of plasma membranes
Involved as cell surface recognition sites (e.g., red blood cells)
Long chain amino alcohol.
Sphingolipids determine this - terminal sugars on sphingolipid determine blood type. Galactose - B, N-acetylgalactosamine = A, N-acetylgalactosamine + galactose = AB, no NAG or GAL = O.
LPS. Bacterial endotoxin, core oligosaccharide - Bacterial internalization,
initiation of immune resistance
Long O-antigen side chains - LPS
Responsible for resistance to human serum, antibiotics, detergents
Lipid A: hydrophobic anchor
Interacts with host TLR4 to initiate inflammatory response
Fever, hypotension, Gram-negative sepsis
One sugar molecule
Galactocerebroside – in neuronal membranes
Glucocerebrosides – elsewhere in the body
Sulfatides or sulfogalactocerebrosides
Sulfuric acid ester of galactocerebroside
Brain lipids, but present in low levels in liver, lung, kidney, spleen, skeletal muscle and heart
Structural lipids that are present in the membranes of most eukaryotic cells. Plants (phytosterols)
Four fused rings
Three = six-membered
One = five-membered
Planar main body
Diffuse freely from the blood through the cell membrane into the cytoplasm of target cells
Only found in animal fat
Primarily synthesized (and only degraded) in the liver
Phytosterols block cholesterol absorption sites in the human intestine
Serves as a component of membranes of cells (increases or moderates membrane fluidity)
Precursor to steroid hormones and bile acids
Storage and transport –cholesterol esters
Oxidized derivatives of sterols
Do not have the alkyl chain found in cholesterol
Increased polarity compared to cholesterol
Move through the blood stream attached to protein carriers
Five groups based on binding receptors:
Vitamin D closely related receptors, but it is technically a sterol
Simple lipids that lack fatty acid component. Formed by the combination of 2 or more molecules of 2-methyl-1,3-butadiene (isoprene)
2 isoprenes c-10
Flavors and odors
Limonene (lemons), citronellal (roses/geraniums), pinene (turpentine), menthol (peppermint)
(C-15) – 3 isoprenes
(C-20) – 4 isoprenes
2 sesquiterpenes C-30
Precursors of cholesterol and other steroids
Not as common as mono, di, and triterpenes
Includes carotenoids (beta-carotene (precursor of vitamin A) and lycopene (tomatoes))
Polyisoprenoids or polyprenols
Consist of numerous isoprene adducts (8 – 22)
Side chains of vitamins K, vitamin E and coenzyme Q
Prostaglandins and Eicosanoids
Key mediators of inflammation
Derivatives of prostanoic acid
Prostaglandins (e.g., PGE1)
Blocks gastric production (gastric protection agents)
Used to treat infants with congenital heart defects
PGF2a – causes constriction of the uterus
Synthesized in neutrophils, monocytes, macrophages, mast cells and keratinocytes
Also found in lung, spleen, brain and heart
Responsible for inflammation in asthma and bronchitis and anaphylaxis
Particles found in plasma that transport lipids including cholesterol
Liver repackages cholesterol (and triglycerides) into lipoproteins
Chylomicrons: take lipids from small intestine through lymph cells
Very low density lipoproteins (VLDL)
Intermediate density lipoproteins (IDL)
Low density lipoproteins (LDL)
High density lipoproteins (HDL)
Different from lipoproteins - proteins with covalently attached lipids - Peripheral membrane proteins. 3 types: Prenylated proteins, Fatty acylated proteins
, Glycosylphosphatidylinositol-linked proteins (GPI-linked proteins).
Glycosylphosphatidylinositol-linked proteins (GPI-linked proteins)
Occur in all eukaryotes, but are particularly abundant in parasitic protozoa
Fatty acylated proteins
Myristoylated and palmitoylated proteins (C14/C16)
Farnesylated and geranylgeranylated proteins (C15/C20 isoprene units)
Esters of long-chain saturated and unsaturated fatty acids with long-chain alcohols
Typically have fairly high melting points
Skin glands secrete waxes to protect hair and skin to keep it pliable, lubricated, and waterproof
Spermaceti – cetyl palmitate
Wax (from whale oil) –useful for pharmaceuticals (creams, ointments, tableting and granulation)
Brazilian palm tree – a hard wax used on cars and boats
Melting/boiling points are not usually sharp (most fats/oils are mixtures) - liquid. If shaken with water, oils emulsify.
Pure fats and oils are colorless and odorless (color and odor result of contaminants)
Butter - bacteria give flavor, carotene gives color
Calcium and magnesium soaps
Very poorly water soluble (hard water contains calcium and magnesium salts that insolubilize soaps)
mixture of sodium and potassium linseed oil
Sodium soap of olive oil
soft soap- shaving soaps are potassium soaps of coconut and palm oils