fatty acids

Fatty acids are best defined as

A hydrocarbon chain with a terminal carboxyl group

Most animal fatty acids have

An even number of carbon atoms

Sources of fatty acids

Fatty acids are obtained from the diet or synthesized de novo in the body

Fatty acids differ in saturation according to

Number of carbon–carbon double bonds

Main classification of fatty acids by saturation

Saturated and unsaturated fatty acids

Saturated fatty acids are defined as

Fatty acids containing no double bonds

Unsaturated fatty acids are defined as

Fatty acids containing one or more double bonds

Classification of saturated fatty acids by chain length

Short-chain (2–10 carbons) and long-chain (>10 carbons)

Short-chain saturated fatty acids contain

2–10 carbon atoms

Long-chain saturated fatty acids contain

More than 10 carbon atoms

Palmitic acid is described as

C16 saturated fatty acid with formula CH3-(CH2)14-COOH

Stearic acid is described as

C18 saturated fatty acid with formula CH3-(CH2)16-COOH

Methods of numbering fatty acid carbon atoms

Carboxyl numbering, α-β-γ system, and ω numbering

In carboxyl numbering, carbon number 1 is

The carboxyl carbon (COOH)

In α-β-γ numbering, counting starts from

The carbon adjacent to the carboxyl group

In ω numbering, counting starts from

The methyl (CH3) carbon

Double-bond position in unsaturated fatty acids is indicated by

Delta (Δ) and omega (ω) systems

In Δ numbering, carbon numbering starts from

The carboxyl group

In ω numbering, carbon numbering starts from

The methyl group

Palmitoleic acid using Δ system

16:1 Δ9

Palmitoleic acid using ω system

16:1 ω7

Unsaturated fatty acids classification by number of double bonds

Monounsaturated and polyunsaturated fatty acids

Monounsaturated fatty acids are defined as

Fatty acids containing one double bond

Example of monounsaturated fatty acid

Palmitoleic acid

Monounsaturated fatty acids are nutritionally

Non-essential

Reason monounsaturated fatty acids are non-essential

They can be synthesized by desaturase enzyme in the liver

Polyunsaturated fatty acids are defined as

Fatty acids containing more than one double bond

Examples of polyunsaturated fatty acids

Linoleic acid, linolenic acid, and arachidonic acid

Classification of unsaturated fatty acids by double-bond position

ω3 and ω6 fatty acids

ω3 fatty acids are characterized by

The first double bond at ω3 carbon

Example of ω3 fatty acid

Linolenic acid

ω6 fatty acids are characterized by

The first double bond at ω6 carbon

Examples of ω6 fatty acids

Linoleic acid and arachidonic acid

Essential fatty acids are defined as

Fatty acids that cannot be synthesized and must be obtained from diet

Essential fatty acids include

Linoleic acid and linolenic acid

Why linoleic and linolenic acids are essential

Human tissues cannot introduce double bonds beyond Δ9

Plants differ from humans in fatty acid synthesis because

They can synthesize essential fatty acids

Dietary sources of essential fatty acids

Sunflower, corn, peanut, cotton seed, and soybean oils

Non-essential fatty acids are defined as

Fatty acids that can be synthesized in the body

Arachidonic acid is formed from

Linoleic acid by elongation and desaturation

EPA and DHA are formed from

Linolenic acid

Parent fatty acid of ω6 series

Linoleic acid

Parent fatty acid of ω3 series

Linolenic acid

Importance of polyunsaturated fatty acids

Formation of phospholipids, membrane fluidity, cholesterol esterification, eicosanoid synthesis, normal growth, and cardiovascular protection

Cardiovascular benefit of ω3 fatty acids

Anti-atherogenic effect reducing ischemic heart disease