Chapter 5 Flashcards
What are the three main types of lipids?
- Structural Lipids
- Signaling Lipids
- Energy Storage Lipids
How do amphiphatic molecules associate in the body (aqueous solutions)?
Amphiphatic molecules will associate themselves in micelles, liposomes, and phospholipid bilayers. Each of these structures is a result of the hydrophobic portions wanting to interact with the water at the exterior of the structure and the hydrophobic portions wanting to interact with eachother in the interior of the structure.
What are the three main types of structural lipids?
- Phospholipids
- Sphingolipids
- Waxes
What are phospholipids?
Phospholipids are a class of molecules with a phosphate and alcohol polar head joined to hydrophobic fatty acid tails by phosphodiester linkages. Note, as long as there is a phosphate on the lipid, the molecule is a phospholipid. DOES NOT NEED GLYCEROL BACKBONE. very loose definition of phospholipid
What is a glycerophospholipid/phosphoglyceride?
Glycerophospholipid is a class of phospholipids. It contains all the lipids with 2 hydrophobic tails attached to a glycerol backbone, attached to a phosphate, and then attached to some kind of head group. The head group is the unique part of a glycerophospholipid, and so the name of the molecule is based on the head group. Have a wide variety of functions including cell recognition, signaling, and binding
In the example below, choline is the head group, but it can be other things.
Phosphatidylcholine
What is a sphingolipid and what are they important for?
Sphingolipid is a class of lipids. It contains all the lipids with hydrophobic tails attached to a sphingosine or sphingoid (which means sphingosine-like, BUT NOT SPHINGOSINE) backbone. Note, all the molecule needs to be a sphingolipid is the sphingosine backbone. If the molecule also has a phosphate group (which a lot of sphingolipids do) it’s a sphingophospholipid. Sphingolipids are important in ABO blood grouping (the difference is in the carb sequence attached)
What is a glycolipid?
A glycolipid is any lipid linked glycosidically linked to a sugar.
What are sphingomyelins?
Sphingomyelins are a major class of sphingophospholipids. Have phosphatidylcholine or phosphatidylethanolamine head groups. These molecules play an important role in the creating and maintaining the myelin sheath.
What is a glycosphingolipid?
A glycosphingolipid is a lipid with a sphingosine backbone and a glycosidically linked sugar
What are Cerebrosides?
Cerebrosides are glycosphingolipids with one sugar connected to sphingosine. Neutral charge
What are globosides?
Globosides are glycosphingolipids with two or more sugars attached to the sphingosine backbone. Neutral charge
What are gangliosides? Function in body?
Gangliosides are a special class of glycosphingolipid (sugar and fat no phosphate) that have polar head groups composed of oligosaccharides with one or more Sialic Acid (N-acetylneuraminic acid, NANA) molecules at the terminus. Gangliosides play an important role in cell interaction, recognition, and signal transduction. Have a negative charge
What are Waxes?
Waxes are esters of long chain fatty acids with long chain alcohols. These molecules have very high van-derwaals interactions and thus form pliable solids at room temperature (like candle wax!). Biologically in both plants and animals, they function as protection and to keep liquids from evaporating.
What are the 4 main types of signaling lipids?
- Terpenes and Terpenoids
- Steroids
- Prostaglandins
- Fat Soluble Vitamins
What are terpenes?
Terpenes are a class of lipids built from isoprene units. They are produced mainly by plants and insects. They are generally strongly scented and they are precursors to steroids. Have aromatic properties due to double bond conjugation
How many isoprenes make up a single terpene unit?
2 isoprenes make one terpene unit. A terpene or terpenoid can be made up of many terpene units.
monoterpenes have 2 isoprenes
sesquiterpenes have 3 isoprenes
diterpenes have 4 isoprenes
triterpenes have 6 isoprenes
tetraterpenes have 8 isoprenes (carotenoids)
What are steroids?
Steroids are characterized by their conserved 4 ring structure (3 cyclohexane and 1 cyclopentane). Note, a steroid is not necessarily a steroid hormone. There are steroids that serve no hormonal function. steroids are mostly nonpolar
What is cholesterol?
Cholesterol is arguably the most significant steroid molecule. It is responsible for mediating membrane fluidity, which means it makes the membrane less fluid at high temperatures and more fluid at low temperatures. It is amphipathic so it interacts with both hydrophillic heads and hydrophobic tails in membranes. Cholesterol is also an important precursor to steroids, bile acids, and vitamin D.
What are prostoglandins? What type of singaling?
Prostoglandins are 20 carbon unsaturated carboxylic acids with a five carbon ring that are derived from arachindonic acid. These molecules act as autocrine and paracrine signalers. They regulate cAMP levels which leads to effects on smooth muscle contraction, the sleep wake cycle, pain, and body temperature.
What is Vitamin A?
Vitamin A (aka Carotene) is an unsaturated hydrocarbon associated with vision, growth, and immune function.
Vitamin A is converted to retinal for use in vision and retinoic acid for regulating gene expression during the growth of epithelial tissues.
What is Vitamin D?
Vitamin D (aka cholecalciferol) is a unsaturated hydrocarbon associated with calcium and phosphate regulationn.
Vitamin D can be consumed or synthesized by the body using exposure to UV light.
In the liver and kidneys, Vitamin D is converted to calcitriol. Calcitriol increases calcium and phosphate uptake in the intestines, which produces better bones.
What is Vitamin E?
Vitamin E (aka tocopherols) is actually a group of lipids called tocopherols and tocotrienols. These lipids all have a substituted aromatic ring with a long isoprenoid side chain,so very hydrophobic. The aromatic ring in vitamin E can capture free radicals safely, protecting us from oxidative damage (cancer and aging).
What is Vitamin K?
Vitamin K is actually a group of compounds. Vitamin K is vital for the creation of prothrombin, an important clotting factor in the blood. It also post-translationally modifies proteins, giving them calcium binding sites. Aromatic ring undergoes oxidation and reduction to form prothrombin
What are triacylglycerols and levels in membranes?
Triacylglycerols (aka tryglycerides) are composed of three fatty acids bonded by ester linkages to glycerol. It is rare for all three fatty acids to be the same. Triacylglycerols are the lipid form of energy storage. Low levels in membranes
What are adipocytes?
Adipocytes are special cells in aminals that store large amounts of triacylglycerols (fat).
What is saponification?
Saponification is the ester hydrolysis of triacylglycerols using a strong base (usually lye, which is just a common name for sodium or potassium hydroxide). Saponification is actually how soap is made! (soap is salts of free fatty acids) Reversed through treatment with acid
What is a colloid?
A colloid is when two or more different phases (gas, solid, or liquid) combine to form what appears to be a single phase. Mixing an insoluble powder in an aqueous phase would make a solid/liquid colloid
How does soap work?
Soap works by creating micelles which capture hydrophobic contaminants inside of themselves. Once the hydrophobic contaminants are contained, the micelles are washed away with water because the hydrophillic heads are now soluble in the water.
