Title: Jack Sparrow Biochem / Biochemistry / Biochemistry Chapter 5
Tags: #JackSparrow::#B/B::#Biochemistry::#Chapter.5

Q: What is a lipid?
A: A lipid is a class of molecules that are characterized by their insolubility in water and solubility in nonpolar organic solvents.  As you can see, the definition of lipid is very broad and the actual structures of the many types of lipids can be radically different, they'll all just be nonpolar/hydropobic.
All of the above are lipids.

Q: What are the 3 main types of lipids?
A: 1.  Structural Lipids
2.  Signalling Lipids
3.  Energy Storage Lipids

Q: What does it mean to be amphiphatic?
A: Amphiphatic molecules are molecules that have both hydrophobic and hydrophilic regions.

Q: How do amphiphatic molecules associate in the body (aqueous solutions)?
A: 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.

Q: What are the three main types of structural lipids?
A: 1.  Phospholipids
2.  Sphingolipids
3.  Waxes

Q: What are phospholipids?
A: 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.
(

Q: What is saturation in the context of hydrocarbon chains?
A: Saturation refers to how many double bonds are in the hydrocarbon chain.  An saturated hydrocarbon tail will have only single bonds.  An unsaturated hydrocarbon tail will have double bonds.  The more double bonds, the more unsaturated the chain.

Q: What effect do double bonds have on phospholipid tails?
A: Double bonds introduce kinks into the fatty acid chain, which makes it difficult for them to stack and solidify.  Therefore, unsaturated fats tend to be liquids at room temperature.

Q: What is a glycerophospholipid?
A: Glycerophospholipid is a class of phospholipids.  It contains all the lipids with 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.
In the example below, choline is the head group, but it can be other things.

Q: What is a sphingolipid?
A: Sphingolipid is a class of lipids.   It contains all the lipids with hydrophobic tails attached to a sphingosine or sphingoid (which means sphingosine-like) 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 phosphosphingolipid.

Q: What is a glycolipid?
A: A glycolipid is any lipid linked glycosidically linked to a sugar.

Q: What are sphingomyelins?
A: Sphingomyelins are a major class of sphingophospholipids.  These molecules play an important role in the creating and maintaining the myelin sheath.

Q: What is a glycosphingolipid?
A: A glycosphingolipid is a lipid with a sphingosine backbone and a glycosidically linked sugar

Q: What are Cerebrosides?
A: Cerebrosides are glycosphingolipids with one sugar connected to sphingosine.

Q: What are globosides?
A: Globosides are glycosphingolipids with two or more sugars attached to the sphingosine backbone.

Q: What are gangliosides?
A: Gangliosides are a special class of glycolipid (sugar and fat no phosphate) that have polar head groups composed of oligosaccharides with one or more Sialic Acid molecules at the terminus.  Gangliosides play an important role in cell interaction, recognition, and signal transduction.

Q: What are Waxes?
A: 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.

Q: What are the 4 main types of signaling lipids?
A: 1.  Terpenes and Terpenoids
2.  Steroids
3.  Prostaglandins
4.  Fat Soluble Vitamins

Q: What are terpenes?
A: 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.

Q: How many isoprenes make up a single terpene unit?
A: 2 isoprenes make one terpene unit.  A terpene or terpenoid can be made up of many terpene units.

Q: What are steroids?
A: Steroids are characterized by their conserved 4 ring structure.  Note, a steroid is not necessarily a steroid hormone.  There are steroids that serve no hormonal function.

Q: What is cholesterol?
A: 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.  Cholesterol is also an important precursor to steroids and vitamin D.

Q: What are prostoglandins?
A: 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 signallers.  They have affect cAMP levels which leads to effects on smooth muscle contraction, the sleep wake cycle, pain, and body temperature.

Q: What is a vitamin?
A: A vitamin is an essential nutrient that cannot be adequately synthesized by the body and therefore must be consumed in the diet.

Q: What is Vitamin A?
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.

Q: What is Vitamin D?
A: 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.

Q: What is rickets?
A: Rickets is a condition seen in children whom lack sufficient vitamin D.  It is characterized by underdeveloped curved long bones as well as impeded growth.

Q: What is Vitamin E?
A: 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.  The aromatic ring in vitamin E can capture free radicals safely, protecting us from oxidative damage.

Q: What is Vitamin K?
A: 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.

Q: What are triacylglycerols?
A: 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.

Q: What are adipocytes?
A: Adipocytes are special cells in aminals that store large amounts of triacylglycerols (fat).

Q: What is saponification?
A: Saponification is the ester hydrolysis of triacylglycerols using a strong base (usually lye, which is just a common name for sodium hydroxide).  Saponification is actually how soap is made!

Q: What is a colloid?
A: A colloid is when two or more different phases (gas, solid, or liquid) combine to form what appears to be a single phase.

Q: How does soap work?
A: 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.