McMurry (Kap. 23,0-23,2) - Lipids (wax, fats, oils, soap) Flashcards
What are lipids?
Occuring biomolecules that have limited solubility in water - can be isolated from organisms by extraction with non polar organic solvents.
Fats, oils, waxes, some vitamins, hormones, and most non-protein cell membrane components are examples.
Lipids are defined by a physical propertie (solubility) rather then the structure.
Lipids are water-insoluble organic molecules, including fats, oils, and steroids, that store energy, form cell membranes, and act as signaling molecules.
Lipids are classified into two broad types, which?
Those like fats and waxes (contain ester linkage and can be hydrolyzed).
Those like cholesterol and other steroids (dont contain ester linkage and cant be hydrolyzed).
What are the chemical structure of waxes?
They consist of mixtures of esters of long chain carboxylic acids with long chain alcohols.
The carboxylic acid usually have even number of carbons from 16-36, while the alcohols also have an even number of carbons from 24-36.
See page 806 for examples.
What are the structures of animal fats and oils?
Animal fat like butter and lard = solids.
Vegetable oil = liquid
Their structures are closely related.
Chemically fats and oils are (triglycerides - triester of glycerol with three long chain carboxylic acids called fatty acids).
(see page 806 for example).
The fatty acids are generally unbranched - contains 12 to 20 carbons.
What is the difference between unsaturated and saturated triglycerides - and what is trans fat?
monounsaturated = only one double bond.
polyunsaturated = have more than one double bond.
If double bonds are present, they have largely (Z or cis geometry) - unfortunately some hydrogenation reactions can make the cis geometry isomerize to trans - reducing its health benefits.
What is an omega 3 fatty acid?
Means that there is a double bond three carbons in from the noncarboxylic end of the chain of the triglyceride.
Do unsaturated or saturated fatty acids have lower melting point?
The unsaturated have lower melting point. Can bee seen on table 23.1 (see page 807). - because of the form which you can read more about on page 808.
What is soap chemically?
Mixture of sodium/pottasium salt of long chain fatty acids produced by hydrolysis (saponification) of animal fat with alkali (wood ash was used back in the day, but now LeBlanc process for making Na2CO3 is used).
How can a soap act as a cleanser?
Because the two ends of a molecule are so different.
The carboxylate end of the chain is ionic (therefore hydrophillic - mixes with water).
The long hydrocarbon portion is hydrophobic - mixes with oils.
Atracts both oils and water making it usefull as a cleanser.
Cluster into micelles when dispersed into water.
