Chapter 18 Lipids

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Chapter 18Lipids

• Types
• Glycerophospholipids
• Sphingolipids
• Steroids

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Lipids contd

• Fig. 19.1
• The structural formulas of these types of lipids
  illustrate the great structural diversity among
  lipids.

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Glycerol 3 FA TAG
Glycerol
Fatty acid (FA)
Triacylglycerol (TAG)
Q. What kind of bonds are these?
A. ESTER!
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Lipids contd

• Fig. 19.5
• Structure of the simple triacyglycerol produced
  from the triple esterification reaction between
  glycerol and three molecules of stearic acid.

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Fatty Acids can be
saturated
monounsaturated
polyunsaturated
Unsaturated, trans or cis-
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Lipids contd

• Fig. 19.6
• Mixed triacylglycerol in which three different
  fatty acid residues are present.

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Physical Properties

• Solid fat
• Liquid oil
• Long ether/alcohol wax
• Melting points depend on length, degree of
  saturation, orientation of double bond (cis or
  trans)

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Lipids contd

• Fig. 19.8
• Percentages of saturated, monosaturated, and
  polyunsaturated fatty acids.

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Chemical Properties

• Reduction (hydrogenation) of unsaturated fatty
  acids
• Removal of double bond
• Oxidation
• Unsaturated FA to aldehyde to carboxylic acid
• Hydrolysis (breaking of ester bond by water
• Q. Products?
• A. Alcohol and carboxylic acid

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Lipids contd

• Fig. 19.10
• Complete and partial hydrolysis of a
  triacylglycerol.

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Lipids contd

• CC 19.3

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Lipids contd

• Fig. 19.11
• Structural equation for the complete
  hydrogenation of a triacylglycerol with oleic
  acid and fatty acid residue.

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Prostaglandins
Arachodonic acid (20 carbons)
Aspirin, NSAIDs
Prostaglandin
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Glycerophospholipids
Phosphoglycerol
Phosphatidic Acid
Headgroups
serine
ethanolamine
choline
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Lipids contd

• Fig. 19.13
• (a) structural formula and (b) molecular model
  showing the head and two tails structure of a
  phosphatidyl-choline molecule.

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Lipids contd

• CC 19.4

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Glycerophospholipids
Phosphatidylcholine (lecithin)
Polar
Non-polar
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Sphingolipids
Sphingosine
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Lipids contd
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Sphingosine
fatty acid (R saturated)
Ceramide
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Ceramide
phosphocholine
sphingomyelin
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Glycosphingolipids
Sugar (galactose)
cerebroside
Ganglioside (GM2)
Lipid Storage Diseases Accumulation of
glycosphingolipids Fabrys Tay Sachs Gauchers Nie
man-Pick
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Steroids
Cholesterol
Sterol nucleus
Fatty acid
Cholesteryl ester
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Steroid Hormones
Testosterone
Estrogen (estradiol)
Progesterone
Norethindrone The Pill
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Lipids contd

• Table 19.4

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Cholesterol TransportLipoproteins
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The Membrane The Fluid Mosaic Model
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Membrane Transport

• Simple Diffusion (Small molecules)
• High concentration to low concentration
• (With concentration gradient)
• Facilitated Transport
• Small ions through pores or channels (proteins)
• (With concentration gradient)
• Active Transport
• Energy-requiring (ATP)
• (Against concentration gradient)

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