Anatomy of a Fatty Acid
The carboxyl head, the carbon chain and its double bonds — saturated, monounsaturated or polyunsaturated — the methyl and omega ends, and chain length from short to very-long.
All fatty acids have a chain of carbons atoms and a head with two oxygen atoms:
Head: At one end sits a carboxyl "head" (–COOH) — a water-friendly group with two oxygen atoms. It's the acidic end, and it's how the fatty acid attaches to other molecules.
Carbon chain: Stretching away from it is a hydrocarbon "tail", or carbon chain: carbon atoms dressed in hydrogens. It is greasy and water-repelling. The carbons are often numbered from the head (C1) to the tail.
Bonds: Every carbon forms 4 bonds with other atoms. Each middle carbon in the chain connects to two hydrogens and two neighbouring carbons.
Double bonds: The exception is a double bond, where two carbons bond to each other twice — so each of them carries only one hydrogen (see C9 and C10 in the example above). Double bonds come in two shapes: cis and trans, which impact the shape and function of the fatty acid. Fatty acids are grouped by how many they have:
Methyl end: The very last carbon in the chain is the methyl end (–CH₃) — it carries 3 hydrogens.
Omega end: The omega number counts from the methyl end back to the nearest double bond, counting both carbons: in the diagram above, C10 through C14 is 5 carbons, so it's an ω-5. (Same result as chain length minus double-bond position: 14 − 9 = 5.) It only applies to unsaturated fatty acids — saturated ones have no double bond to count to.
Chain length: Simply how many carbons are in the tail. Shorter fatty acids pass through barriers more easily; longer ones are handled more slowly and need to be packaged for transport. Lengths are classified as:
Other fatty acids: Note there are other fatty acids types, these will be covered in other sections.
Free to move: Note these fatty acids are flexible: the carbons can rotate around single bonds, and the angle of the bonds as well as the bond length has a bit of flex.
Explore and interact with these fatty acids in 2D and 3D:
Head: At one end sits a carboxyl "head" (–COOH) — a water-friendly group with two oxygen atoms. It's the acidic end, and it's how the fatty acid attaches to other molecules.
Carbon chain: Stretching away from it is a hydrocarbon "tail", or carbon chain: carbon atoms dressed in hydrogens. It is greasy and water-repelling. The carbons are often numbered from the head (C1) to the tail.
Bonds: Every carbon forms 4 bonds with other atoms. Each middle carbon in the chain connects to two hydrogens and two neighbouring carbons.
Double bonds: The exception is a double bond, where two carbons bond to each other twice — so each of them carries only one hydrogen (see C9 and C10 in the example above). Double bonds come in two shapes: cis and trans, which impact the shape and function of the fatty acid. Fatty acids are grouped by how many they have:
- Saturated (SFA): no double bonds
- Monounsaturated (MUFA): a single double bond
- Polyunsaturated (PUFA): two or more double bonds. Omega-3s and Omega-6s are well known PUFAs.
Methyl end: The very last carbon in the chain is the methyl end (–CH₃) — it carries 3 hydrogens.
Omega end: The omega number counts from the methyl end back to the nearest double bond, counting both carbons: in the diagram above, C10 through C14 is 5 carbons, so it's an ω-5. (Same result as chain length minus double-bond position: 14 − 9 = 5.) It only applies to unsaturated fatty acids — saturated ones have no double bond to count to.
Chain length: Simply how many carbons are in the tail. Shorter fatty acids pass through barriers more easily; longer ones are handled more slowly and need to be packaged for transport. Lengths are classified as:
- short-chain (about 2–5 carbons)
- medium-chain (6–12)
- long-chain (13–21)
- very-long-chain (22 or more)
- C17:0 is a FA with 17 carbons, and no double bonds (hence SFA).
- C16:1 Ω-7 is a FA with 16 carbons, 1 double bond (hence MUFA), and an omega 7 (7 carbons from last double bond to end)
- C18:2 n-6 is a FA with 18 carbons, 2 double bond (hence PUFA), and an omega 6 (6 carbons from last double bond to end)
Other fatty acids: Note there are other fatty acids types, these will be covered in other sections.
Free to move: Note these fatty acids are flexible: the carbons can rotate around single bonds, and the angle of the bonds as well as the bond length has a bit of flex.
Explore and interact with these fatty acids in 2D and 3D: