Fatty Acid Nomenclature | Part 3 Lipid Foundations | Macronutrients Lecture 69

Summary

This video explains the two primary systems for naming fatty acids: the nutritional/biochemical nomenclature and the chemistry nomenclature. In the biochemical context, fatty acids are named based on the number of carbons, double bonds, and the position of the first double bond from the methyl end, using omega (or n) notation. In the chemistry context, the carbon count starts from the carboxyl end, and delta notation is used to indicate the positions of the double bonds. The video uses the example of linoleic acid to illustrate both systems, providing clarity on how fatty acids are categorized in different fields.

Takeaways

• 😀 Fatty acids are named based on the number of carbons, the number of double bonds, and the position of the first double bond.
• 😀 In nutritional and biochemical contexts, fatty acids are counted from the methyl (omega) end, with carbon number one being at this end.
• 😀 To name a fatty acid, we first count the carbons in the chain, determine the number of double bonds, and locate where the first double bond appears.
• 😀 The term 'omega' refers to the position of the first double bond when counting from the methyl end of the fatty acid tail.
• 😀 An example of a fatty acid is linoleic acid, which has 18 carbons, 2 double bonds, and the first double bond at carbon number 6 (omega-6).
• 😀 Omega-6 fatty acids are commonly referred to as 'n6' in literature and can be abbreviated this way.
• 😀 In chemistry contexts, fatty acids are named starting from the carboxyl end of the molecule.
• 😀 Chemistry nomenclature uses the Greek letter 'delta' to indicate the position of each double bond in a fatty acid chain.
• 😀 Using the chemistry nomenclature, linoleic acid would be named 18:2 delta-9,12 to indicate two double bonds at positions 9 and 12.
• 😀 The omega nomenclature is preferred in nutritional and biochemical contexts, while delta-based naming is more common in chemical contexts.

Q & A

What is the primary factor used to name a fatty acid?

The primary factors used to name a fatty acid are the number of carbons, the number of double bonds, and the position of the first double bond.

In the nutritional/biochemical context, which end of the fatty acid tail is counted as carbon number one?

In the nutritional/biochemical context, the methyl end of the fatty acid tail is counted as carbon number one.

How do we denote the position of the first double bond in a fatty acid using the omega system?

In the omega system, the position of the first double bond is denoted by the omega number, which indicates how far the double bond is from the methyl (omega) end of the fatty acid.

What is the nomenclature for an 18-carbon, 2-double-bond fatty acid with the first double bond at carbon 6?

The nomenclature for this fatty acid in the omega system is 18:2 omega-6.

Why is the omega system used in the nutritional context, and what does the term 'omega' signify?

The omega system is used in the nutritional context because it is simpler and more intuitive. The term 'omega' refers to the last letter of the Greek alphabet, denoting the position of the first double bond from the methyl (omega) end.

How does the chemical nomenclature system differ in counting the carbons in a fatty acid?

In the chemical nomenclature system, carbons are counted starting from the carboxyl end (opposite of the methyl end) of the fatty acid.

What does the delta (Δ) symbol represent in the chemistry nomenclature system?

In the chemistry nomenclature system, the delta (Δ) symbol is used to indicate the positions of double bonds within the fatty acid chain.

How would an 18-carbon, 2-double-bond fatty acid with the first double bond at carbon 9 be named in the chemical nomenclature system?

In the chemical nomenclature system, this fatty acid would be named 18:2 Δ9,12.

What is the main difference between the omega and delta systems for naming fatty acids?

The main difference is that the omega system counts carbons from the methyl end of the fatty acid, while the delta system counts from the carboxyl end and uses Greek letters like delta (Δ) to specify the exact positions of double bonds.

Why might the omega system be preferred in general nutritional or biochemical discussions?

The omega system is preferred in general discussions because it is simpler and more practical for non-chemists, focusing on the position of the first double bond from the methyl (omega) end of the fatty acid.