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Lipid Properties

Lipids are a class of organic molecule composed primarily of hydrocarbon chains (fatty acids) or rings (steroids) 

  • Hydrocarbons are non-polar (they lack charged regions) and will not dissolve in polar substances like water

  • Hence lipids are considered to be hydrophobic molecules (they are water-repelling)

The hydrophobic properties of lipids have many important biological consequences

  • Waxes are used to prevent water loss from leaves while birds coat their feathers with oil to render them waterproof

  • Phospholipids provide a structural framework for cells by forming spontaneous membranes in aqueous solutions

  • Lipids in foods help the body to absorb certain fat-soluble micronutrients, including vitamins A and D

However, the hydrophobic properties of lipids make them difficult to transport around the body 

  • Digested fats are packaged within a protein coat to become water soluble lipoproteins

  • Steroid hormones are bound to carrier proteins (such as albumin) to facilitate their movement through the bloodstream

Certain lipids have polar components, becoming amphipathic (having both hydrophobic and hydrophilic regions)

  • Phospholipids possess a polar phosphate head, cholesterol has a polar hydroxyl group and glycolipids can have polar carbohydrate chains

  • These amphipathic molecules all have a limited capacity to interact with water, helping them to function in maintaining membrane integrity

Water Repellant Surfaces
1 4%20linkage
Bird Feathers (Oil)
1 6%20linkage
Leaf Cuticles (Wax)