Lipid Nutritional Biochemistry

Lipid Nutritional Biochemistry

• Lipids are organic compounds containing carbon, hydrogen, and oxygen (C, H, O).
• They are insoluble in water, but soluble in fat solvents like ether, alcohol, benzene, and chloroform.
• Lipids are not polymers; they are not formed from repeating units like polysaccharides.

Functions of Lipids

• Efficient energy sources
• Thermal insulators
• Component of cell membranes
• Involved in steroid hormone synthesis
• Crucial for the absorption and digestion of fat-soluble vitamins (A, D, E, K).

Classification of Lipids

• Simple Lipids: Neutral fats (e.g., fats and oils) and waxes
• Compound Lipids: Phospholipids, glycolipids, and lipoproteins
• Derived Lipids: Fatty acids, alcohols, and sterols

Simple Lipids

• Neutral fats: Esters of fatty acids and glycerol.
  • Liquid at room temperature: Oils
  • Solid at room temperature: Fats
  • Also known as Triglycerides (TAG)

Fatty Acids

• Saturated: No double bonds
• Unsaturated: Contain double bonds
  • Monounsaturated: One double bond
  • Polyunsaturated: Two or more double bonds
  • Examples: Stearic acid, oleic acid, linoleic acid, linolenic acid, arachidonic acid
• Important for cell membrane structure and function

Phospholipids

• Major component of cell membranes
• Structure: 2 fatty acids + phosphate head
• Fatty acid chains are hydrophobic; phosphate head is hydrophilic

Lipoproteins

• Transport lipids in the bloodstream
• Different types (e.g., VLDL, LDL, HDL) with varying lipid and protein composition
• Important role in cardiovascular health

Waxes

• Solid at room temperature
• Insoluble in water
• Protective covering for animals and plants (e.g., beeswax, earwax, cuticle of leaves)

Biological Functions of Lipids

• Energy Storage: Provide high energy (9 kcals/gram), stored as adipose tissue, comprising 60% of body energy
• Insulation & Protection: For thermal protection, insulation and protection of organs
• Health Effects: Excess fat intake can lead to diseases like obesity, diabetes, and cancer.

Dietary Recommendations

• Limit total fat intake to <30% of total calories.
• Limit cholesterol intake to <300 mg/day.
• Limit saturated and polyunsaturated fats to <10% of total calories each.