Lipids Greek: lipos, fat Chemical diverse set of molecules that are insoluble in water

Other Lipid Characteristics Not polymers Aggregation — e.g. bilayers (membranes) Greatest structural variation of major biomolecules

Major Classes of Lipids

Functions of Lipids Biological Membranes (bilayers) Energy Stores Signaling –Intracellular –Intercellular

Fatty Acids (Simplest Lipids) Amphiphilic/Amphipathic Usually esterified form in nature Saturated and unsaturated Usually even number of carbon atoms

SaturatedUnsaturated Fatty Acids

Some C 18 Fatty Acids (cis double bonds)

Omega naming ω ω ω-3 fatty acidω-6 fatty acid

Common Biological Fatty Acids

Triacylglycerols Constitute ~90% of Dietary Lipid Major form of Metabolic Energy Storage in Humans Simple: all the same fatty acid Mixed: different fatty acids

Page Palmitoleoyl-2-linoleoyl-3-stearoylglycerol

Importance of Triacylglycerols (Adipocytes and Adipose Tissue) Energy Resevoirs –Less oxidized than carbohydrates and amino acids –Anhydrous versus hydrated glycogen –6x energy yield versus glycogen –2-3 month energy supply versus <1 day for glycogen Thermal Insulation Not components of biological membranes

Figure 9-2 Adipocytes (Scanning Electron Microscope)

Glycerophospholipids ( Amphiphilic) C16 or C18 Saturated C18 or C20 UNsaturated

Figure 9-3a Glycerol-3-phosphate

C16-18 C18-20

Glycerophospholipids ( Amphiphilic) Non- Polar Tail Polar Head

Figure Stearoyl-2-oleoyl- 3-phophatidyl choline Non- Polar Tail Polar Head

Figure 9-5 Action of Phospholipases ( Determination of Structure)

Figure 9-6 Model of Phospholipase A 2 and a Glycerophospholipid

Action of Phospholipases (Formation of Signal Molecules) Lysophosphatidic Acid Blood Platelets — Wound Repair

Action of Phospholipases (Formation of Signal Molecules) Diacylglycerol Signaling Cascade

Sphingolipids Sphingosine Head group Fatty acid

Glycolipids

Figure 9-7a A Sphingomyelin

Figure 9-8 Myelinated Nerve Fiber (Electron Microscopy)

Sphingolipids and Phospholipids have similar physiochemical properties

Sphingolipids (Cerebrosides) Non-ionic Membrane Lipid

Sphingolipids (Gangliosides)

Figure 9-9b Ganglioside G M2

Importance of Gangliosides Cell Surface Receptors –Hormones –Toxins Determinants of Cell-Cell Recognition Disorders of Ganglioside Breakdown –Tay-Sachs disease – fatal neurological breakdown

Page 254 Steroids (Steroid Core Structure)

Cholesterol

Figure 9-10a Cholesterol Numbering

Figure 9-10b Cholesterol Structure

Page 254 Cholesterol Ester

Importance of Cholesterol Major Component of Animal Plasma Membranes (and to a lesser extent organelle membranes) Precursor of Steroid Hormones

Page 257 Isoprenoids (Isoprenoid Precursor)

Page 257 Isoprenoid Example (Coenzyme Q)

Lipid Summary Sparingly soluble in water Not polymers – aggregates Diverse Functions –Biological membranes –Energy stores –Signaling molecules