Storage Lipids and Reactions Quiz

Storage Lipids

• Triacylglycerols are also known as triglycerides or fats.
• They are the most abundant class of lipids and serve as energy stores in animals, specifically in adipocytes.
• Triacylglycerols consist of a glycerol molecule esterified to three fatty acid residues.
• There are two types: simple triacylglycerols (all three fatty acids are the same) and mixed triacylglycerols (at least two different fatty acids).

Reactions of Triacylglycerols

• Hydrogenation:
  • The reduction of double bonds in unsaturated fatty acids to convert them into solid, saturated fatty acids.
  • This process uses hydrogen gas and a catalyst (Pt or Pd).
• Saponification:
  • The process of making soap from fats or oils.
  • It involves reacting fats or oils with a base to form a surfactant (soap) in a hydrolysis reaction.

Waxes

• Esters of fatty acids and alcohols.
• The fatty acids in waxes are usually saturated.
• The alcohols in waxes can be saturated or unsaturated.
• Waxes are highly insoluble in water.
• Examples:
  • Lanolin (used as a base for pharmaceutical products)
  • Carnauba wax (used as floor and automobile wax)

Structural Lipids

• Major component of cell membranes.
• Two types:
  • Phospholipids
  • Glycolipids

Phospholipids

• Glycerophospholipids:
  • Also called phosphoglycerides.
  • The major lipid component of animal biological membranes.
  • Amphiphilic molecules (contains both polar and nonpolar parts).
  • Have glycerol as their backbone.
  • Most glycerophospholipids have phosphatidic acid as the parent compound.
• Derivatives of Phosphatidic Acid:
  • Phosphatidylcholine:
    • X = choline
  • Phosphatidylethanolamine:
    • X = ethylamine
  • Phosphatidylserine:
    • X = serine
  • Phosphatidylinositol:
    • X = myo-inositol
• Sphingolipids:
  • Class of lipids usually found in biological membranes.
  • Have sphingosine as their backbone.

Glycolipids

• Galactolipids:
  • Also called sulfolipids
  • The major lipid component of plant cell membranes.
  • Makes up approximately 70-80% of plant lipids in chloroplasts.
• Gangliosides:
  • Found in animal cell membranes, particularly nerve cells.

Signaling Lipids

• Eicosanoids:
  • Paracrine hormones derived from arachidonic acid (a 20-carbon polyunsaturated fatty acid).
  • Classified into three types:
    • Prostaglandins
    • Thromboxanes
    • Leukotrienes
  • Mediators of:
    • Inflammation
    • Fever and pain
    • Progression or termination of pregnancy
    • Regulation of blood pressure
    • Menstruation
• Steroids:
  • A large, terpene-based class of lipids.
  • All steroids have a common structural motif consisting of four rings fused together.
  • The most common steroid and precursor of all animal steroids is cholesterol.
  • Cholesterol is an important component of animal cell plasma membranes and regulates the fluidity of the membrane.

Cholesterol

• Synthesis:
  • Synthesized by all animal cells from Acetyl-CoA.
• Function:
  • Important component of animal cell plasma membranes.
  • Regulates the fluidity of the membrane.