Triacylglycerols

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Affiliations

Doctor of Physical Therapy

B.S. in Kinesiology

Doctor of Physical Therapy

B.A. in Neuroscience

Also known as triglycerides or neutral fats.

Structure

Triacylglycerols are composed of 3 fatty acids, each in ester linkage. An ester linkage is a chemical bond between an acid and an alcohol. In triacylglycerols, the ester linkage consists of an acid (fatty acid) and it is chemically bound to an alcohol (glycerol).

Function

Triacylglycerols are nonpolar and hydrophobic molecules since the polar hydroxyls of glycerol and the polar carboxylates of the fatty acids are bound in ester linkages. Due to their nonpolar and hydrophobic state, triacylglycerols are essentially insoluble in water, which is crucial for their role in energy storage.

Simple & Complex

Triaglyceroles consisting of a single type of fatty acid in all 3 positions is called “simple triacylglycerols” and are named after the fatty acid.

Example
  • Palmitic acid (16:0) simple triacylglycerol → Tripalmitin
  • Stearic acid (18:0) simple triacylglycerol → Tristearin
  • Oleic acid (18:1) simple triacylglycerol → Triolein
Note

Most naturally occurring triacylglycerols are mixed

To name non-simple triacylglycerols without ambiguity, the name and position of each fatty acid must be specified.

Role in Energy Storage

In vertebrates, triacylglycerols are stored in specialized cells called “adipocytes”, or “fat cells”. These adipocytes store large amounts of triacylglycerols as fat droplets that nearly fill the cell.

Versus polysaccharides

Triacylglycerols have 2 significant advantages that make it better for energy storage than polysaccharides (starch or glycogen).

  1. Fatty acid carbon atoms are more reduced and therefore yield more (>2x) energy
  2. Triacylglycerols are hydrophobic and do not need to be hydrated. Oppositely, polysaccharides need to be hydrated and thus require the organism to carry extra water to maintain polysaccharide hydration.

Triacylglycerols can hold much more energy (weeks to months) than glycogen. Glycogen has its benefits since it can produce metabolic energy quicker due to their water solubility.

Serum

Blood test for serum triglycerides

References

1.
Nelson DL, Cox MM, Hoskins AA. Lehninger Principles of Biochemistry. 8th ed. Macmillan Learning; 2021.

Citation

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