Untitled Quiz

Complex Lipids

• Complex lipids form biological membranes
• They spontaneously form lipid bilayers in aqueous solutions
• Hydrophilic head groups face the aqueous environment
• Hydrophobic tails are buried within the bilayer
• Hydrophobic interactions drive the formation of bilayers
• The arrangement of tails can be rigid (saturated) or fluid (unsaturated)

Phospholipids

• Similar to triacylglycerol but replace one fatty acid with a phosphate group and an amino alcohol
• Contains an alcohol, two fatty acids, and a phosphate ester
• Can be degraded by phospholipases

Glycerophospholipids

• Also known as phosphoglycerides
• The second most abundant lipids in the body
• Component of cell membranes
• Similar structure to fats but with glycerol as the alcohol
• Two hydroxyl groups esterified with fatty acids
• Third hydroxyl group esterified with phosphoric acid, which is also bonded to another alcohol
• Most common are derived from phosphatidic acid, which has glycerol esterified with two fatty acids and one phosphate
• Fatty acid on carbon 2 of glycerol is always unsaturated
• Further esterification with an alcohol (e.g. choline or ethanolamine) forms a glycerophospholipid

Glycerophospholipids: Lecithin

• Glycerophospholipid with choline attached to phosphate ester
• Major component of egg yolk
• Excellent emulsifier due to its polar and nonpolar components

Glycerophospholipids: Cephalins

• Glycerophospholipids with ethanolamine or serine attached to a phosphate ester
• Found in cell membranes

Glycerophospholipids: Phosphatidylinositols (PI)

• Inositol is bonded to phosphate group
• Phosphorylated forms, such as PIP2, act as signaling molecules in cell communication

Sphingolipids

• Contain sphingosine, a long-chain amino alcohol
• Myelin, a sphingolipid, is found in the coatings of nerve axons
• Ceramide part can incorporate various fatty acids like stearic acid
• Found in cerebrosides

Glycolipids

• Complex lipids containing carbohydrates and ceramides
• Carbohydrate is usually glucose or galactose
• Cerebrosides are ceramides with mono- or oligosaccharides, found in the brain and nerve synapses
• Gangliosides have more complex carbohydrates

Derived Lipids: Steroids

• Contain a steroid nucleus, a tetracyclic ring structure with three cyclohexane rings and one cyclopentane ring
• Differ in functionality due to substituent groups attached to the core structure
• Rings are designated A, B, C, and D
• Carbons are numbered starting from ring A and ending at methyl groups

Cholesterol

• Most abundant steroid in humans
• Component of cell membranes
• Precursor for other steroid hormones like bile salts, vitamin D, and sex hormones