• insoluble in water
• soluble in non-polar solvents like chloroform, benzene

Due to these characteristics, these compounds are structurally heterogeneous

Vitamins K, A, E

• aliphatic group attached to a carboxyl group
• can be branched or be straight chained
• 90% of FA's have even number of carbons
  • most common are 16, 18, or 20 carbons

• short chain (less than 6 C's)
• medium chain (6-12 C's)
• long chain (12-20 C's)
• very long chain (more than 20 C's)

• monounsaturated- one double bond FA
• polyunsaturated- more than one double bond FA

• saturated- stearic acid
• monounsaturated- oleic acid
• two double bonds- linoleic acid
• three double bonds- linolenic acid

Describe the omega numbering system for fatty acids

• used for polyunsaturated FA's
• start numbering from the methyl end of the fatty acid as oppose to the carboxylic acid end
• ω-3 series FA's have the first double bond occur three carbons from the methyl end

Disadvantage of trans-FA's

• they become incorperated into the membrane
• this will alter packing of these lipids, leading to loss of membrane integrity

What is the role of the number of carbons in solubility and melting point? DB's?

• the more carbons, the less solubility
• the more carbons, the higher the melting point
• the more double bounds, the lower the melting point (unsat. FA's liquid at room temperature)

• plant fat has a higher ratio of unsaturated to saturated fatty acids than animal fat
• plant fat liquid at room temperature
• lard/animal fat is solid at room temperature

• ionization (go from acid to the -ate form)
• neutralization (treat with NaOH to form the salt)- any salt of a FA is a soap
  • if I use calcium or magnesium (divalent cations), this soap is insoluble
• ester formation (FA with alcohol produce ester)
  • if its a FA and "fatty" alcohol, produce wax

• reduction- add hydrogen to eliminate DB
• oxidation- form short chain aldehydes, as well as lipid peroxides and free radicals
  • dialdehydes are volitale and cause rancid smell of fat

Essential dietary FA's

• linoleic acid- 18 C's w/DB at 9, 12
• linolenic acid- 18 C's w/DB at 9, 12, 15
• arachidonic acid- 20 C's w/DB at 5, 8, 11, 14

We can synthesize in the body all the SATURATED FA's the body needs

• add DB's at any position in the fatty acid up to and including position 9 (common at positions 4, 5, 6, and 9)
• this means we can't insert a DB into the 12th position of a C18 FA, so you cant make linoleic acid (DB at 9, 12) or linolenic acid (DB at 9, 12, 15)

1. via 6 desaturase, add DB to the 6 position of linoleic acid (C18 with DB at 9, 12) (now have DB at 6, 9, 12 w/18 C's)
2. elongation via acetyl CoA at the end of the FA (now have DB at 8, 11, 14 and 20 C's)
3. via 5 desaturase, add DB at 5 position (now have arachodonic acid- DB at 5, 8, 11, 14 and 20 C's)

FA's synthesized from linolenic acid

• eicosapentaenoic acid (EPA) (20 C's with 5,8, 11,14,17)
• docosahexaenoic acid (DHA) (22 C's with double bonds at 4,7,10,13,16,19)

Both are MAJOR omega 3 FA's found in fish oil

• synthesis of
  • PG's
  • thromboxanes
  • leukotrienes
  • lipoxins

• brain development
• normal function of membranes of rods and cones of eye

sterols

steroids

Vitamin K, A, E

Describe the dietary need of cholesterol

• essential component of membrane
• precursor to many biological compounds like bile salts and hormones of adrenal cortex