lecture 1: chemical composition of fatty acids/lipids

solubility

hydrophobic molecules

• fatty acids and their derivatives are insoluble in water

triglycerols/triglycerides and waxes

used as energy stores

phospholipids

found in membranes

• used as structural molecules

• 2 ethyl chains

other lipids

steroids, act as signals, co-factors (vitamin E,K) and pigments (carotene, chlorophyll)

• carotene:

hydrophobic tails of fatty acids

• can be made of 4-36 carbons in length (always an even number)

• head group: made of a carboxylic acid

• saturated and unsaturated varieties

• unsaturated; kinks in the chain due to double C=C bonds

stores of energy; triglycerols/triglycerides

glycerol linked by an ester bond to 3 fatty acids

• triglyceride made of glycerol moiety

• each of the hydroxyls in glycerol in glycerol will be linked to an aliphatic tail to form the tri

saturated fats

• fully hydrogenated

• no double bonds in the carbon backbone

• close packing molecules

• often found in mammals

unsaturated fats

• one or more fouble bonds in teh carbon backbone

• double bonds result in kinks in teh fatty acid ‘tail’

• close packing is hindered by the kinks

• typically stored in plants

phospholipids

structural lipids

• composed of a glycerol molecule linked to 2 fatty acid molecules and a phosphate group

• this structure provides them with amphipathic properties ( hydrophilic phosphate head; polar, hydrophobic fatty acid tail; non-polar)

membranes

• Phospholipids arranged into a bilayer

• Hydrophobic tails shielded from water

• Hydrophilic heads exposed to water

• Major component: Phosphatidylcholine (PC)

• Membranes perform vital functions in cells

membranes

• fluid structures

• Phospholipid molecules are not covalently linked together in the membrane

• Lipid molecules are in constant lateral motion

• Unsaturated phospholipids enhance membrane fluidity

• Saturated phospholipids are closely packed and less fluid due to the lack of double bonds

• The ratio of saturated : unsaturated lipid determines the membrane fluidity and can change with an organism's environment