Classification of lipids

1
Classification of lipids

• Simple lipids (non saponifiable)
• terpenes, steroids, prostaglandins
• Complex lipids (saponifiable)
• acylglycerols
• waxes Fatty acids
• phospholipids covalently linked
  sphingolipids different backbones

2
Waxes

• simple esters of fatty acids (usually saturated)
  with long chain monohydric alcohols

Beeswax also includes some free alcohol and
fatty acids Spermaceti contains cetyl palmitate
(from whale oil) useful for pharmaceuticals
(creams/ointments tableting and
granulation) Carnauba wax from a palm tree from
brazil a hard wax used on cars and boats
3
Spermaceti source
Carnauba wax source
Bees wax
4
Phospholipids

• Have hydrophobic and hydrophilic domains.
• Structural components of membranes
• Emulsifying agents
• Suspended in water they spontaneously rearrange
  into ordered structures
• Hydrophobic group to center
• Hydrophilic group to water (basis of membrane
  structure)

5
PhospholipidsPhosphoglycerides

• When the third OH of glycerol is esterified to a
  phosphoric acid or a phosphoric acid ester
  instead of a carboxylic acid, a
  phosphoacylglycerol results.

Phosphatidyl ester
Phosphatidic acid
6
Phosphatidyl esters
ethanolamine (cephalin) choline (lecitin) serine
(phosphatidyl-serine) inositol (phosphatidyl-in
ositol)
Common constituent of membrane lipid
Involved in cell signalling
7
Phospholipids
Amphipatic molecule
8
Sphingolipids

• These lipids are based on sphingosine, are found
  in plants and animals, and are common in the
  nervous system.

9
Sphingolipids
ceramide N-acylsphingosine
sphingomyelin
A ceramide with phosphocholine or
phosphoethanolamine as head group
10
Sphingoglycolipids

• Attachment of carbohydrates to primary -OH of
  ceramide
• Cerebrosides contain a single moiety,
  principally galactose
• Sulfatides sulfuric esters of galactocerebrosides
  
• Gangliosides contain a complex oligosaccharide
  moiety

11
Sphingoglycolipids-2
a cerebroside
These compounds are found in the cell membranes
of nerve and brain cells.
12
Clinical significance of sphingolipids
Blood groups determined by various glycolipids on
RBCs
13

• Membranes An Overview
• Continuous, unbroken sheets, enclosing
  compartments
• Dynamic structures capable of fusing without
  losing continuity
• External membrane
• plasma membrane encloses contents of entire
  cells
• Internal membranes
• nuclear envelope
• mitochondrial membranes
• chloroplast membranes
• lysosomal membrane
• endoplasmic reticulum

14
The Cell Membrane

• Maintains cellular stability and integrity
• Is a protective and selective barrier
• Controls and directs cellular activity
• Each type of cell has a unique membrane
  composition with varying percentages of lipids,
  proteins, and some carbohydrates.
• The currently accepted model of the membrane is
  the fluid mosaic model of a lipid bilayer.

15
Composition of Some Membranes
16
Components of Membranes
17
Membrane Structure

• Lipid bilayer
• Hydrophillic heads in contact with aqueous
  environment
• Hydrophobic tails reside in interior of bilayer
• Cholesterol is a structural component
• Proteins
• Integral
• Peripheral
• Lipid anchored
• Dynamic structure

18
Fluid mosaic model
a. lipid bilayer is core of membrane b. lipid
molecules are present in a fluid state capable of
rotating and moving laterally within
membrane. c. proteins occur as mosaic of
discontinuous particles. d. some proteins
penetrate deeply into, and even through, lipid
bilayer. e. membranes are dynamic structures in
which components are mobile.