Post on 12-Jan-2016
LipidsGreek: 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
COO–
Saturated Unsaturated
Fatty Acids
Some C18 FattyAcids
(cis double bonds)
Omega naming
987654321
ω
ω-3 fatty acidω-6 fatty acid
Common Biological Fatty Acids
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
O
CH
H2C O
C R1H2C
O
C
O
R3
Fatty AcidsOCR2
O
Glycerol
Fatty Acid
Page 248
1-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)
O
CH
H2C O
C R1H2C
O
P
O
O–
O R3 Alcohol
Fatty Acid
OCR2
O
Glycerol
Fatty Acid
Phosphate
C16 or C18Saturated
C18 or C20UNsaturated
Figure 9-3a
Glycerol-3-phosphate
C16-18
C18-20
Glycerophospholipids(Amphiphilic)
O
CH
H2C O
C R1H2C
O
P
O
O–
O R3 Alcohol
Fatty Acid
OCR2
O
Glycerol
Fatty Acid
Phosphate
Non-PolarTail Pola
rHead
Figure 9-4
1-Stearoyl-2-oleoyl-3-phophatidyl choline
Non-PolarTail
PolarHead
Figure 9-5
Action of Phospholipases(Determination of Structure)
Figure 9-6
Model of Phospholipase A2
and a Glycerophospholipid
Action of Phospholipases(Formation of Signal Molecules)
O
CH
H2C O
C R1H2C
O
P
O
O–
O–
HO Lysophosphatidic Acid
Blood Platelets — Wound Repair
Action of Phospholipases(Formation of Signal Molecules)
Diacylglycerol
Signaling Cascade
O
CH
CH2OH
C R1H2C
O
OCR2
O
Sphingolipids
CH3(CH2)12 CH CH CH
OH
CH
CH2OH
NH2
Sphingosine
Head group
Fatty acid
Glycolipids
Figure 9-7a
A Sphingomyelin
Figure 9-8
Myelinated Nerve Fiber(Electron Microscopy)
Sphingolipids and Phospholipidshave similar physiochemical
properties
Sphingolipids(Cerebrosides)
Non-ionic Membrane Lipid
CH3(CH2)12 CH CH CH
OH
CH
CH2
OSugar
HN C
O
R
Fatty Acid
Sphingolipids(Gangliosides)
Figure 9-9b
Ganglioside GM2
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
HO
CH3
CH3
CH
CH3
CH2 CH2 CH2 CH
CH3
CH3
Flexible Hydrophobic Tail
Hydrophilic(Polar Head)
Rigid Fused Ring
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