In nature are fatty acids generally found in their free form or incorporated into triacylglycerols?
They are normally found incorporated into triacycglycerols
What are the 2 basic forms fatty acids come in?
Saturated and Unsaturated
Describe saturated fatty acids
simplest and least reactive
Chain series of methyl groups terminating in an carboxyl group
Structurally a zig-zag but linear overall
What length of saturated fatty acids are liquid at room temperature?
Why does water solubility decrease with increasing chain length?
Increasing hydrophobicity as the methyl chain extends and dominates the more polar carboxyl group
Which fatty acids are slightly miscible with water?
What special properties do the monovalent salts of free fatty acids have?
They are water soluble, with strong surface tension reducing properties (bubbles!!)
Why cant soaps be used as emulsifiers?
Although they are excellent emulsifiers, they taste awful
When do you get soapy off flavors in food?
When metal ions in food react with a free fatty acid
What is soap scum?
Divalent ion salts are largely insoluble so when it reacts with hard water it makes soap scum
What are the two naming systems for fatty acids?
Systematic names (IUPAC)
Which names tend to predominate?
What is the common name of 'ethanoic acid'?
What is the common name of butanoic acid?
What is the common name of hexanoic acid?
What is the common name of octanoic acid?
What is the common name of decanoic acid?
What is the common name of dodecanoic acid?
What is the common name of hexadecanoic acid?
What is the common name of octadecanoic acid?
What is the common name of eicosanoic acid?
What is the common name of docosanoic acid?
What are fatty acids with one double bond called?
What does a cis double bond do to the molecular structure?
Introduces a kink which can make an L or U shape, depending on where the double bond is located
What does a single trans bond make a fatty acid look like?
Appear more like a saturated fatty acid than an unsaturated fatty acid
What is the order of melting points?
Cis < Trans < Saturated
Is it easier for trans-monounsaturated or cis-monounsaturated to for a crystal latice?
Trans-monounsaturated (mono-cis = bandaids)
What is a common and generally unavoidable side effect of hydrogenation?
Conversion of cis isomers to trans
Fun Fact: cis-trans conversion to a large degree is the main mechanism by which oils are converted into plastic fats during hydrogenation, moreso than the accompanying desired reduction in the overall degree of unsaturation
Why are trans fatty acids consider to be un-natural fatty acids?
Because they are not found in nature
Are trans fatty acids metabolized more like saturated or unsaturated fatty acids?
More like saturated eventhough they are unsaturated
Why does butter naturally contain trans fatty acids?
Due to bio-hydrogenation of cis fatty acids to trans by reumen miroorganisms
What does positional isomerism affect?
The physical properties of monounsaturated fats, because of where the double bond is located
In IUPAC nomenclature, where is the double bond position counted from?
Which is a more significant variable: positional isomerism or cis/trans configuration
cis/trans configuration is more significant
What is an example of when the position of a double bond an be very important?
Omega-3 fatty acids
What are the two basic forms of how double bonds are situated relative to each other?
unconjugated: they are separated by methylene carbon
Conjugated: next to eachother
Are most natural polyunsatured FAs conjugated or unconjugated?
What is the most famous naturally occuring conjugated fatty acid?
Conjugated linoleic acid (CLA) which has both cis and trans double bonds
What is special about CLA (Conjugated Linoleic Acid)?
It is considered to have anti-carcinogenic effects, anti-arteriosclerotic effects, help the immune system and affects energy metabolism
Are conjugated or unconjugated FAs more thermodynamically stable?
Are conjugated or unconjugated FAs more susceptible to autoxidation?
What is an active methylene group?
The methyl group in linolenic acid that is positioned between double bonds which are conjugated on one side and unconjugated on the other
Contributes substantially to reversion phenomenon
What are the most common unsaturated fatty acids?
Oleic, Linoleic, Linolenic
How is the presence of a double bond indicated in the nomenclature?
Ending becomes -enoic instead of -anoic
If there is more than one double bond, the count is given before the suffix
How is the location of the double bond indicated in the nomenclature?
Counting from the carboxyl end, put the number of the carbon that the double bond starts at before the full name
How do you indicate cis/trans configuration in the nomenclature?
Put either cis or trans before every number
What is the omega carbon?
The last carbon which tells you to count from the CH3 end instead
Why are omega-3 fatty acids considered beneficial?
They slow the development of arteriosclerosis
What does straight chain variety mean?
The fatty acid has no branches or side groups or chains
Describe branched chain fatty acids
They have a hydrocarbon branch in the chain
They contain a cyclopropene ring
Why is the cyclopropene ring bad for chicken eggs?
It makes pasty and rubbery yolks and causes egg color problems
Describe hydroxy acids
Contain a hydroxyl group in the fatty acid chain (very reactive)
Found in the oil of the castor bean tree
What are acetylinic fatty acids?
Contain a triple bond
What are some other functional groups which may be present in the fatty acid chain?