Lipids and Fatty Acids Flashcards
How are lipids defined?
Lipids are defined by their solubility in non-polar solvents (a physical property) rather than by chemical structure
What type of structures do lipids have?
Many lipids have hydrocarbon or modified hydrocarbon structures , properties and behaviours
What are triesters?
Naturally occurring fats/oils formed between glycerol and fatty acids.
They are long, unbranched, hydrocarbon chains with a COOH group at one end
How do you differentiate between saturated and unsaturated fatty acids?
saturated have no double bonds, unsaturated do have double bonds
unsaturated fatty acids can be cis or trans
What are fats and oils composed of and a difference between the two?
All fats and oils are composed of triesters of glycerol with 3 fatty acid chains
fats are typically solids, whilst oils are liquids
What contributes to the difference in melting point between saturated and unsaturated fatty acids?
Saturated fatty acids tend to have higher melting points than unsaturated fatty acids due to the difference in 3D shape.
Double bonds in unsaturated fatty acids allow for the formation and cis and trans isomers and add ‘kinks; to the hydrocarbon chain
This results in poorer packing, lower density and less intermolecular interaction
How can rancidity be reduced + example!
When C=C double bonds in vegetable oils are hydrogenated to yeild saturated fats
For example solid cooking fats produced commercially by the hydrogenation of vegetable oils. This creates trans fats
How are natural soaps prepared?
Through an ester hydrolysis reaction.
- Natural soaps are prepared by boiling lard or other animal fat with NaOH, a reaction called saponification
How do soaps assemble into micelles?
They are driven by hydrophillic and hydrophobic reactions to self assemble the different parties near/away from the water
Why do soaps work as cleaning agents?
Because the two ends of a soap molecule are so different. The ionic end is hydrophillic; it tends to dissolve in water. The long hydrocarbon chain portion of the molecule is non polar and hydrophobic.
When soap is mixed with water- insoluble grease, oils and fats, the non polar parts of the soap micelles “dissolve” the dirt and it is carried away in the polar wash water
What occurs when soaps are used in water containing Ca2+, Mg2+, or Fe3+?
It forms insoluble salts
What are synthetic detergents made of?
Long hydrocarbon tails of 12-20 carbons with a polar head group that doesn’t form insoluble ions
What are phospholipids derived from?
Mostly derived from phosphatic acid-glycerol esterified with 2 fatty acids and 1 phosphoric acid
The further esterification of this molecule with a lower molecular weight alcohol gives a phospholipid
What role do phospholipids play in cell membranes?
Phospholipids provide the basic structure of cell membranes, where they aggregate in a closed, sheet like, double leaflet structure called the lipid bilayer
What occurs when the lipid bilayer is shaken with water?
The bilayer is highly ordered and stable but still flexible
when phospholipids are shaken vigorously with water, they spontaneously form liposomes
liposomes are small spherical vesicles with a lipid bilayer surrounding an aqueous centre
