Lipids Flashcards
Phospholipids
contain a phosphate and alcohol that comprise the polar head group, joined to a hydrophobic fatty acid tail by phosphodiester linkages
Saturated Fatty Acid
- tails that only have single bonds
- carbon atom is considered saturated when it is bonded to 4 other atoms with no pi bonds
- greater van der waals forces and stable overall structure
- solid at room temperature
- high melting point
- decrease membrane fluidity
Unsaturated Fatty Acid
- has one or more double bonds, or rings
- liquid at room temperature
- increase membrane fluidity
- create kinks in chain so inhibition of stacking and solidifying
- at low temperatures these help increase membrane fluidity
Glycerophospholipids
- phospholipids that contain a glycerol backbone bonded by ester linkages to two fatty acids and a phosphodiester linkage to a highly polar head group
- named according to their head group
Sphingolipids
- have a sphingosine or sphingoid backbone that is a long carbon chain that becomes one of the nonpolar tails of the lipid
- long-chain nonpolar fatty acid tails and polar head groups
- contain a phosphodiester linkage or glycosidic linkages to sugars
- sites of biological recognition at cell surface
Glycolipid
any lipid linked to a sugar
What are the 4 subclasses of spingolipids?
- ceramide
- sphingomyelins/sphingophospholipids
- glycosphingolipids
- gangliosides
Ceramide
has a single hydrogen atom as its head group
Sphingomyelins
- major component of cells that produce myelin
- type of sphingophospholipid
Sphingophospholipid
- sphingolipids that are also phospholipids
- head group is either phosphatidylcholine or phosphatidylethanolamine so contain a phosphodiester bond
- head groups don’t have a net charge
Glycosphingolipids
- sphingolipids with head groups composed of sugars bonded by glycosidic linkages
- type of glycolipid, not a phospholipid
- found on outer surface of membrane
- no net charge
Gangliosides
- glycolipids with polar head groups made of oligosaccharides with one or more N-acetylneuraminic acid (NANA) molecules at the terminus
- contain glycosidic linkages
Waxes
- contain long-chain fatty acids esterified to long-chain alcohols, do not have a polar head group
- used as protection against evaporation and parasites in plants/animals
- entirely nonpolar and hydrophobic
- pliable solids at room temp
- most soluble in pure organic solvents (“like dissolves like”)
- prevent water loss across the plasma membrane
Terpenes
- chemicals that are the metabolic precursors to steroids and other lipid signaling molecules
- lipids built from isoprene (C5H8) moieties
Monoterpenes
- contain 2 isoprene units
- C10H16
Sesquiterpenes
contain 3 isoprene units
Diterpenes
- contain 4 isoprene units
- Ex. Vitamin A
Triterpenes
- contain 6 isoprene units
- can be converted to cholesterol and other steroids
Tetraterpenes
- contain 8 isoprene units
- Ex. carotenoids
Terpenoids
- isoprenoids
- derivatives of terpenes that have undergone oxygenation or rearrangement of carbon skeleton
- contribute to steroid biosynthesis
Steroids
- signaling lipid
- have 4 cyclo-alkane rings fused together
- nonpolar
- Ex. cholesterol
Steroid Hormones
- secreted by endocrine glands into bloodstream then travel on protein carriers to distant sites
- can alter gene expression levels and metabolism
Cholesterol
- major component of phospholipid bilayer
- mediates membrane fluidity
- amphipathic (both hydrophobic and hydrophilic)
- precursor to steroid hormones, bile acid, and vitamin D
What does cholesterol do for the membrane at high temperatures?
keeps membrane intact by moving phospholipids closer together and thus decreasing membrane fluidity
What does cholesterol do for the membrane at low temperatures?
increases distance between phospholipids and thus increasing membrane fluidity
Progstaglandins
- produced by nearly all cells in body
- 20-carbon molecules with unsaturated carboxylic acid derived from arachidonic acid (contain one 5 carbon ring)
- downstream effects including regulation of cAMP synthesis, smooth muscle function, influence on sleep-wake cycle, and increased body temperature
What vitamins are fat soluble?
A, D, E, K
Vitamin
- essential nutrient
- not adequately synthesized by body so must include in diet
Vitamin A (Carotene)
-unsaturated, hydrocarbon important in vision, growth/development, immune function
Retinal
- metabolite of vitamin A
- often bound to protein opsin
- converts light energy in photons to chemical energy
Retinol
- storage form of vitamin A
- can be oxidized to retinoic acid (hormone that regulates gene expression during epithelial development)
Vitamin D (Cholecalciferol)
consumed and formed by UV light driven reaction in skin
Calcitriol
- form that the liver and kidneys convert vitamin D to
- biologically active form of vitamin D
- increases calcium and phosphate uptake in intestines
Vitamin E
- group of lipids called tocopherols (biological antioxidants) and tocotrienols
- characterized by substituted aromatic ring with long isoprenoid side chain
- hydrophobic
- help prevent oxidative damage
Vitamin K
- vital to post-translational modifications required to form prothrombin (blood clotting factor)
- required to introduce calcium-binding sites on calcium-dependent proteins
Triacylglycerols
- used for energy storage
- oxidation of these results in 2x the amount of energy per gram as carbs
- hydrophobic. insoluble in water
- composed of 3 fatty acids bonded by ester linkages to glycerol
- nonpolar
Adipocytes
special cells in animals that store large amounts of fat
Free Fatty Acids
unesterified fatty acids with free carboxylate group
Saponification
ester hydrolysis of triacylglycerols using a strong base
Surfactant
- lowers the surface tension at the surface of a liquid
- serves as a detergent or emulsifier
What phosphoglyceride is abundant in mitochondrial membranes?
Diphosphatidylglycerol (Cardiolipin)
12:0
Laurate
14:0
Myristate
16:0
Palmitate
18:0
Stearate
20:0
Arachidate
16:1
Palmitoleate
18:1
Oleate
18:2
Linoleate
20:4
Arachidonate
What are the 10 common phosphoglycerides found in membranes?
- Serine
- Ethanolamine
- Choline
- Inositol
- Glycerol
- Phosphatidylcholine
- Phosphatidylethanolamine
- Phosphatidylserine
- Phosphatidylinositol
- Diphosphatidylglycerol
What kind of bond is found in Triacylglycerol?
glycerol with 3 carbon chains bound by ESTER LINKAGES
What is the general structure of a phospholipid?
glycerol, 2 FA tails, PO4 bonded to ROH (alcohol)
What is the general structure of a Phosphatide?
glycerol, 2FAs, PO4
What type of bond is found in Sphingomyelin?
Amide Link
Which is more stable/less reactive, an amide link or an ester link?
Amide Link
What does it mean to glycosylate a phospholipid?
add sugar (glycosylate) to a fat
What is a cerebroside?
- it is a phospholipid that has a sugar attached (glucose, galactose)
- the sugar is almost always found on the extracellular side of the membrane
All ___ hormones are derived from cholesterol
steroid
Cholesterol in the membrane ___ fluidity at high temperatures. It does this by increasing __ __ ___ interactions.
- decreases
- van der waals
The presence of cholesterol in the membrane __ boiling
prevents
In general, cholesterol ___ membrane fluidity. It does this by ___ FA tails of lipids from packing and sticking together.
- increases
- preventing
Cholesterol is considered ___ because it has a polar -OH group, but is mostly nonpolar overall.
amphipathic
Prostaglandins are ____ molecules derived from ___ ___
- signaling
- fatty acids (specifically arachidonate)
Fat Soluble Vitamins are ___ for enzymes that are non-polar.
cofactors
