Lipids and Fatty Acids Overview

Lipids

• Lipids are organic compounds, esters of fatty acids or associated with these esters
• Classified into three groups:
  • Simple lipids: esters of fatty acids with alcohols
  • Conjugated lipids: esters of fatty acids and alcohols plus other non-lipid components
  • Derived lipids: compounds from the hydrolysis of simple or conjugated lipids, or are associated with lipids

Fatty Acids (R - COOH)

• Monocarboxylic organic acids, mostly containing an even number of carbon atoms
• Carbon skeleton numbered from carboxyl group or methyl group (omega carbon)
• Two main groups of fatty acids:
  • Saturated fatty acids (SFA): no double bonds
  • Unsaturated fatty acids (USFA): one or more double bonds

Saturated Fatty Acids (SFA)

• Include:
  • Short-chain fatty acids (up to 10 carbons): examples include butyric acid (C4) and caproic acid (C6)
  • Long-chain fatty acids (more than 10 carbons)

Unsaturated Fatty Acids (USFA)

• Most double bonds are cis-type, causing bending and lower melting points (liquid at room temperature)
• Classified into two types based on the number of double bonds:
  • Monoenoic acids: one double bond. Examples include oleic acid (18:1), nervonic acid (24:1)
  • Polyenoic acids (PUFAs): more than one double bond (e.g., dienoic, trienoic, etc.). Examples include linolenic acid (18:3) and linoleic acid (18:2)
• Classified into families based on the position of the first double bond from the omega (ω) carbon (methyl CH3)

Nutritional Classification of Fatty Acids

• Essential fatty acids: not produced by the human body, must be obtained from the diet (linolenic, linoleic, arachidonic acids)
• Non-essential fatty acids: produced by the human body

Chemical Properties of Fatty Acids

• Ester formation: glycerol + 3 fatty acids = triacylglycerol
• Salt formation: fatty acids react with alkalis to form salts (soaps)
• Hydrogenation: addition of hydrogen to unsaturated fatty acids converts them to saturated fatty acids

Rancidity

• Development of bad odour and taste in fats and oils due to moisture, oxygen, and high temperature
• Two types:
  • Hydrolytic rancidity: caused by moisture and bacterial lipase enzymes, leading to the formation of volatile fatty acids
  • Oxidative rancidity: caused by the formation of peroxides and aldehydes from unsaturated fatty acids

Simple Lipids

• Esters of fatty acids with alcohols
• Classified into neutral fats (triacylglycerols) and waxes

Neutral Fat

• Esters of three fatty acids with glycerol, also known as triglycerides (TAG)
• Classified into two groups:
  • Oils: low melting point, liquid at room temperature (high content of unsaturated fatty acids – USFA)
  • Solid fats: high melting point, solid at room temperature (high content of saturated fatty acids – SFA)

This quiz explores the fundamental concepts of lipids and fatty acids, including their classifications and characteristics. Understand the differences between simple, conjugated, and derived lipids, as well as the properties of saturated and unsaturated fatty acids. Test your knowledge on the structure and function of these essential biomolecules.