Lipids

• lipids are another important class of nutrients that include fatty acids, phospholipids, steroids, and cholesterol
• primary functions will be discussed further in lipid classifications

  • source of energy
  • Energy storage
  • Cell membrane component
  • Protection and insulation
  • Digestion and absorption
• fatty acids consist of a long hydrophobic, non-polar hydrocarbon “tail”, and a hydrophilic polar carboxylic acid functional group at the “head”
• natural fatty acids may be classified as

  • saturated fatty acids
  • unsaturated fatty acids
• saturated fatty acids have no carbon-carbon double bonds
• unsaturated fatty acids contain one or more double bonds in the hydrocarbon chain
• lauric acid - a saturated fatty acid found in coconut oil
• Oleic acid - an unsaturated fatty acid found in animal fat
• essential fatty acids

  • Linoleic acid
  • Linolenic acid
• Essential fatty acids are precursor in the sentences of prostaglandins. A group of lipids greatly affects a number of important physiological process.
• trans fats or trans fatty acids can be formed through a process called hydrogenation, which makes the oil more solid
• the cis and trans configurations influence the shape of fatty acid molecules
• trans configuration that twist or kink produced by the double bond in the cis configuration is not observed
• trans fats can be found in many food products such as

  • Cookies
  • Cakes
  • Savory snacks
• classification of lipids

  • simple lipids
  • Complex lipids
• steroids are simply lipids that have a backbone structure, consisting of four fused carbon rings
• cholesterol is the most abundant steroid in animal tissues. It is composed of steroid backbone structure with hydroxyl group at one end and a branched hydrocarbon chain at the other.
• cholesterol serves us

  • Base of other steroids
  • Male and female hormones
  • Vitamin D
  • Bile acid
• The most abundant class of lipids in plants and animals is that triglycerides
• triglycerides are composed of

  • Three fatty acids
  • Single glycerol
• esterification is the reaction between an alcohol and a carboxylic acid that produces an ester and water
• Triglycerides are the major lipids found in the blood
• at room temperature, solid triglycerides usually of animal origin are called fats
• liquid triglycerides, usually from plants are called oils
• phospholipids are the fundamental building blocks of cellular membranes
• phospholipids are have two distinct parts

  • Hydrophilic phosphate head
  • Long hydrophobic tail
• lecithin is an example of phospholipid. It is a major component of cell membrane and this use as an modifying agent
• lecithin is naturally found in

  • Egg yolks
  • nut
  • Whole grains
  • Soybeans
• another phospholipid is cephalin, which is found in the cell membranes of the brain and tissue and in blood platelets
• waxes are water-insoluble, low-melting solids that consist of a long chain fatty acid and a long chain, monohydroxy alcohol
• Types of waxes

  • Beeswax
  • Chinese wax
  • Earwax
  • lanolin
  • shellac
  • Spermaceti
  • Vegetable wax
• Phospholipids are made up of two fatty acids, glycerol, phosphate, and one simple organic molecule