Lipid Notes

• Diverse group of molecules
• Fatty acids
• Triglycerides
• Steroids
• Phospholipids
• These are macromolecules.  They do not necessarily fit into the definition of polymers

Fats and Oils

• These are primarily energy storage molecules
• Triglycerides that are solid at room temperature are fats
• Triglycerides that are liquid at room temperature are called oils
• Triglycerides are composed of the molecules Glycerol and three fatty acids
• The fatty acids are connected to glycerol by and ester bond
• The fatty acids attached to the glycerol can be varied.

• Saturated fatty acids have all single bonds.  These form rigid,straight chains
• Unsaturated fatty acids have one or more double bonds.  This causes a kink in the chain.  The bottom fatty acid in the picture shows the effect of a double bond
• The double bonds affect the melting point and fluidity of the fatty acids
• The fatty acids in corn oil are short and unsaturated.  This type has a low melting point and is generally a liquid at room temperature
• The fatty acids in animal fats are packed tightly toegher.   These are generally solids at room temperature.  Like lard and butter
• Fats and oil are stoerhouses for energy.  Plant species have seeds like sesame, sunflower, and nuts  that contain substantial amounts of lipids in their seeds
• Trans and cis – most vegetable oils have cis bonds.  If the oil is used more than once the bonds can change to trans.  Trans bonds are not as healthy

Phospholipids

• Phospholipids are composed of a glycerol molecule, two fatty acid chains ( this is the hydrophobic portion) and a head made of phosphatidylcholine which is hydrophilic
• The phosphate end of the phopholipid faces the outside of the membrane and possesses a negative charge
• The hydrophobic chains of fatty acids face the interior of the membrane
• The membrane is a double layer( BILAYER) which we will study independently in a chapter

Carotenoids

• The carotenoids are a family of light absorbing pigments found in plants and animals.
• Beta carotene is essential to the process of photosynthesis
• Beta carotene can be broken down into two vitamin A molecules
• The pigment rhodopsin which is essential for vision is produced from this molecule
• Carotenoids are responsible for the colors of carrots, yellow squash, egg yolks and butter.

Rhodopsin in your eyes - links

http://www.chemsoc.org/exemplarchem/entries/2002/upton/rhodopsin.htm

Steroids

·         Family of organic compounds with multiple rings

·         They contain a steroid nucleus

·         They act as signal molecules – some are classified as hormones

·         Vitamins also belong to this category

·         Cholesterol is the basis in structure for these molecules

·         Cholesterol is synthesized in the liver – used to regulate lipid levels in the body

·         Testosterone and estrogen are sex hormones that regulate sexual development and sexual activity

·         Cortisol is a regulatory hormone that affects the metabolism of carbohydrates and proteins.  It also affects the salt balance and water balance.

Waxes

·         Found on animal hair

·         On the outside of feathers

·         Plant leaves have an exterior waxy coating as do some fruits

·         Bees make their honey combs out of wax

·         All waxes have the same structure.  They are formed by an ester linkage between a saturated, long-chain fatty acid and a saturated, long- chain alcohol.  Their chain consists of molecules that are 40-60-CH2 groups in length