Ch 5 - Lipid Structure And Function Flashcards
Lipid
Characterized by insolubility in water and solubility in nonpolar organic solvents
Amphipathic
Molecules with this characteristic have a hydrophilic and a hydrophobic region. Polar head is hydrophilic. The fatty acid tail is hydrophobic
Phospholipids
Contain a phosphate and an alcohol that comprise the polar head group joined to a hydrophobic fatty acid tail by phosphodiester linkages
Glycerol
3 carbon alcohol
Forms phosphoglycerides or glycerophospholipids
Saturated fatty acid
The tails have only single bonds
Carbon bond is considered saturated when it is bound to 4 other atoms with no pi bonds
Greater van der Waals forces and more stable structure
Unsaturated fatty acid
Includes one or more double bond which introduce kinks into the fatty acid chain which makes it difficult for them to stack and solidify
Glycerophospholipids
Also called phosphoglycerides
Phospholipids that contain a glycerol backbone bonded by ester linkages to two fatty acids and by a phosphodiester linkage to a highly polar head group
Sphingolipids
Sphingosine or sphingoid backbone
Not all are phospholipids
Glycolipid
Any lipid containing glycosidic bonds to sugar
Four major subclasses of sphingolipids
Ceramides
Sphingomyelins
Glycosphingolipids
Gangliolipids
Ceramide
Major class of Sphingolipid with single hydrogen atom as its head group
Sphingomyelins
Major class of sphingolipids that are also phospholipids
Have either phosphatidylcholine or phosphatidylethanolamine as a head group and thus contain a phosphodiester bond
Major component in plasma membranes of cells producing myelin, the insulating sheath for axons
No net charge
Glycosphingolipids
Major class of sphingolipids that are also glycolipids Not phospholipids, ie no phosphodiester linkages mainly found on outer surface of plasma membrane Further classified as either cerebrosides or globosides
Cerebrosides
Glycosphingolipids with a single sugar
No net charge at physiological pH
Globosides
Glycosphingolipids with two or more sugars
No net charge at physiological pH
Waxes
Esters of long chain fatty acids with long chain alcohols
Terpenes
Metabolic precursors to steroids and other lipid signaling molecules
Class of lipids built from isoprene (C5H8) moieties which share a common structural pattern with carbons grouped in multiples of 5
Monoterpenes (C10H16) Sesquiterpenes Diterpenes Triterpenes Tetraterpenes
Mono have two isoprene units and 10 Cs
Sesqui - 3 isoprene with 15 Cs
Di- 4 isoprenes with 20 Cs (vit A)
Tri - 6 isoprenes with 30 Cs - converted to cholesterol and various other steroids
Tetra - 8 isoprenes with 40 Cs - Carotenoids
Polyterpene- a lot (rubber)
Terpenoids
Also called isoprenoids
Derivatives of terpenes that have undergone oxygenation or rearrangement of the carbon skeleton
Steroids
Metabolic derivatives of terpenes
Characterized by having four cycloalkane rings fused together: three cyclohexane and one cyclopentane
Functionality is determined by oxidation status of these rings as well as functional groups they carry
Steroid hormones
Steroids that act as hormones meaning they are secreted by endocrine glands into the bloodstream and then travel on protein carriers to distant sites where they can bind to specific high affinity receptors and alter gene expression (testosterone, various estrogens, cortisol, and aldosterone)
Cholesterol
Steroid - major component of phospholipid bilayer and responsible for mediating membrane fluidity
Amphipathic
Precursor to steroid hormones, bile acids and vit D
Prostaglandins
Produced by almost all cells in the body. 20-carbon molecules are unsaturated carboxylic acids derived from arachidonic acid and contain one 5-carbon ring
Many cells responsible for regulating synthesis of cyclic adenosine monophosphate cAMP which then moderates many other hormones
Raises body temp associated with fever and pain - NSAIDS inhibit
Fat soluble vitamins
Vitamin A (carotene) Vitamin D (cholecalciferol) Vitamin E (tocopherols and tocotrienols) Vitamin K (phylloquinone K1, and menaquinones K2)
Vitamin A
Carotene unsaturated hydrocarbon important for vision, growth and development and immune function
Most significant is aldehyde form - retinal important for light sensing
Retinol is storage form and can be oxidized to retinoic acid - a hormone that regulates gene expression during epithelial development
Vitamin D
Cholecalciferol
Consumed in the form of UV light driven reaction with skin
In liver and kidneys is converted to calcitriol (biologically active form of vitamin D)
Increases calcium and phosphate uptake in intestines
Vitamin E
Closely related lipids called tocopherols and tocotrienols
Characterized by substituted aromatic ring with a long isoprenoid side chain and are hydrophobic
Prevents oxidative damage
Vitamin K
Group of compounds including phylloquinone (K1) and menaquinones (K2)
Important for production of prothrombin important clotting factor for blood
Also introduces calcium binding sites in several calcium-dependent proteins
Triacylglycerols
Also called triglycerides
Composed of three fatty acids bonded by ester linkages to glycerol
Great for storing energy because carbon atoms of fatty acids are more reduced than those of sugars which yields twice the amount of energy per gram as carbs
And they are hydrophobic do not draw in water or require it
Observed as oily droplets in cytosol
Adipocytes
Cells that store large amounts of fat found primarily under skin, around mammary glands, and in abd cavity
Saponification
Ester hydrolysis of triacylglycerols using a strong base
Surfactant
Soap after saponification lowers surface tension at surface of a liquid
Soap can “mix” hydrophobic and hydrophilic substances into a colloid and dissolve both hydrophobic on inside of micelles and hydrophobic on outside
Gangliosides
Major and most complex group of sphingolipids
Polar head groups composed of oligosaccharides with one or more N-acetylneuraminic acid (NANA or sialic acid) molecules at the terminus
Have a negative charge
No phosphate group so considered glycolipids
Play a major role in cell interaction, recognition, and signal transduction
