Biol 217-Lecture 2- Lipids 1: Lipids and Membranes

Lipids 1: Lipids and membranes 

What are lipids?

• Diverse class of molecules
• Rich in Carbon and Hydrogen, but few Oxygen molecules
• Most are not soluble in water
• Many are amphiphathic
• They have a Polar, hydrophillic head and a Non polar hydrophobic tail

Lipids are split into Fatty acids (Eicosanoids, Triacylglycerols, Waxes, Sphingolipids), Phospholipids (Phosphatidates), Glycolipids and Polyprenyl compounds (Steroids).

Fatty Acids

• There are over 100 different fatty acids
• R-COOH structure
• They differ in level of unsaturation and the length of their hydrocarbon tail
• Their melting point depends on their degreee of unsaturation and position of the double bonds
• Saturated= no C=C e.g. Stearate (C18)
• Monounsaturated= 1 C=C e.g. Oleate (C18)
• Polyunsaturated= more than one C=C e.g. Linolenate (C18)
• Omega fatty acids (w) e.g. "w-3 fatty acid"- 20C,double bond every 3 Carbons, w on 1
• "Cis and trans" fatty acids- e.g. Oleic aid (Cis) and Elaidic acid (Trans)

Fatty acid in the living cell

• C12-C20, even number
• Free fatty acids only in traces
• Essential fatty acids

Triacylglycerols (Triglycerides)

• A triacylglycerol molecule is a Glycerol compound with 3 fatty acids attached via an Ester bond. O=C-O
• Triacylglycerols are the most abundant lipids in human food
• Fats: Solid at room temperature, Long-chained, saturated fatty acids
• Oils: Liquid at room temperature, Shorter-chained, more unsaturated fatty acids
• Triacylglycerols storage- They have a high energy content and hydrophobic. Anhydrous storage and form adipocytes. 
• They are the most abundant lipids in mammals
• They are NOT found in membranes
• They are NOT amphipathic

Glycerophospholipids

• Most abundant lipids in biological membranes
• Amphipathic
• Glycerol…