Lipids Detailed Notes

Saturated Lipids

  • Have the maximum number of hydrogen atoms possible.
  • Have no double bonds in their carbon chain.
  • Are solid at room temperature.

Unsaturated Lipids

  • Have one or more double bonds.
  • Oils are examples.
  • They are liquids at room temperature.
  • When hydrogenated (by adding more hydrogen), they become solid and saturated.

Fatty Acid Bonding Structure

  • Saturated fatty acids: single bonds.
  • Unsaturated fatty acids: contain at least one double bond.

Trans Fats

  • Trans unsaturated fatty acid (trans fats):
    • The chemical process used to saturate unsaturated fatty acids can lead to trans fats.
    • These have a double bond that results in a linear chain.
    • Do not form naturally.
    • Do not function well in biological systems.
    • Are a health hazard.
    • trans double bond vs cis double bond

Trans Fat: Margarine

  • Margarine is a trans fat that was developed during World War II.
  • Due to a milk and butter shortage, scientists took corn oil and hydrogenated it.
  • The double bonds became single bonds, and a solid was formed.

Health Hazards of Trans Fats

  • Trans fats tend to stay in the bloodstream much longer than saturated or unsaturated fats.
  • Trans fats are much more prone to arterial deposition and plaque formation.
  • Scientists have studied whether trans fats could play a role in the following diseases and disorders:
    • Cancer
    • Alzheimer's disease
    • Diabetes
    • Obesity
    • Liver dysfunction
    • Infertility
    • Their role remains unclear.

Amphiphilic Lipids: Soaps and Detergents

  • The hydrophobic end of a soap or detergent is repelled by water but attracted to other non-polar molecules, like grease and oil.
  • The hydrophilic end of the soap or detergent forms hydrogen bonds with water.

Soaps and Detergents

  • The soap or detergent bonds with many stains (oil, grease, etc.), pulls them from the surface being cleaned and into micelles in the surrounding water.
  • The water and micelles then go down the drain, along with the oil or grease, leaving the surface clean.

Waxes

  • Waxes are effective hydrophobic coatings formed by many organisms (insects, plants, humans) to ward off water.
  • They often consist of 2 long fatty acids connected by oxygen-containing groups.

Steroids

  • Lipids with backbones that form rings.
  • Examples:
    • Cholesterol is an important component of cell membranes.
    • Male and female sex hormones, testosterone and estrogen, are also steroids.
    • Cortisol is a stress-related hormone.