Biochemistry: Lipids and Esterification

Saponifiable Lipids

• Saponifiable lipids include simple lipids (e.g., triglycerides), complex lipids (e.g., phospholipids, sphingolipids), and waxes.
• These lipids can undergo hydrolysis.

Nonsaponifiable Lipids

• Nonsaponifiable lipids include steroids and prostaglandins.
• These lipids cannot undergo hydrolysis because they lack ester bonds.

Esterification

• Esterification is the process of linking a fatty acid to an alcohol.
• This process is crucial in forming triglycerides, a crucial component of fats and oils.
• This is a dehydration synthesis reaction

Fatty Acids

• Fatty acids are typically straight-chain hydrocarbons.
• They typically have 10-20 carbons.
• They can be saturated (no carbon-carbon double bonds) or unsaturated (containing carbon-carbon double bonds).
• The presence of double bonds correlates inversely with the melting point.

Functional Group for Saponification

• The functional group in saponifiable lipids that allows basic hydrolysis is the ester group.

Triglyceride Hydrolysis

• In the presence of a strong base like sodium hydroxide (NaOH), triglycerides undergo saponification.
• This process breaks down triglycerides into glycerol and soap molecules (fatty acid salts).

Essential Fatty Acids

• Essential fatty acids (e.g., linoleic acid, linolenic acid) cannot be synthesized by the body.
• They must be obtained from the diet.

Glycerol Structure

• Glycerol contains a hydroxyl functional group.
• This functional group makes glycerol an alcohol.

Lipid Membrane Structure

• Cell membranes are primarily composed of lipids (around 60%) and proteins (around 40%).
• Lipids form a bilayer structure where the hydrophobic tails face each other and hydrophilic heads face the water environment.

Steroid Classification

• Steroids are classified as lipids because they are largely composed of carbon and hydrogen atoms; they are insoluble in water but soluble in organic solvents.

Unit Conversions

• 1 pound = 0.453592 kilograms
• 1 gram = 0.001 kilograms