Transcript 1.Lipid intro finalx

Lipids
• Lipids: a heterogeneous class of naturally
occurring organic compounds (mainly esters)
classified together on the basis of common
solubility properties
Lipids
• Lipids include
– ESTERS
– Triacylglycerols (triglycerides),
phosphoacylglycerols (phospholipids),
sphingolipids, glycolipids.
– NON-ESTERS
– cholesterol, steroid hormones, and bile acids
– lipid-soluble vitamins, and prostaglandins
Waxes
• Waxes are very water insoluble and high melting
point.
• They are widely distributed in nature as protective
waterproof coatings on leaves, fruits, animal skin,
fur, feathers and exoskeletons
Prentice Hall c2002
Chapter 9
8
Waxes
• Esters of long-chain fatty acids and long chain
monohydroxylic alcohols
– from the Old English word weax = honeycomb
O
O
CH3 ( CH2 ) 1 4 CO( CH2 ) 3 0 CH3
CH3 ( CH2 ) 3 0 CO( CH2 ) 3 3 CH3
A major component of beeswax
A major component of
(honeycombs)
carnauba wax
(the Brazilian wax palm)
O
CH3 ( CH2 ) 1 4 CO( CH2 ) 1 5 CH3
A major component of
spermacetti wax
(head of the s perm whale)
Triacylglycerols
• Esters of glycerol with
three fatty acids
• Fatty acids are stored
as neutral lipids,
triaclyglycerols (TGs)
• TGs are hydrophobic,
stored in fat cells
(adipocytes)
Prentice Hall c2002
Chapter 9
Structure of a
triacylglycerol
10
Glycerophospholipids
Name and Formula
Name of Phospholipid
ethanolamine
- OCH2 CH2 N H2
phosphatidylethanolamine
(cephalin)
choline
+
- OCH2 CH2 N ( CH3 ) 3
phosphatidylcholine
(lecithin)
serine
- OCH2 CHCO2
phosphatidylserine
N H3
+
Glycerophospholipids
inositol
-O
HO
glycerol
OH
HO
phosphatidylinositol
OH
OH
phosphatidylglycerol
OH
- OCH2 CHCH2 OH
phosphatidylglycerol
diphosphophaticylglycerol
OH
O
O
(cardiolipin)
- OCH2 CHCH2 OPOCHOCR3
O - CH2 OCR4
O
Structures of
glycerophospholipids
Prentice Hall c2002
Phosphatidylcholine (PC)
Chapter 9
13
Structures of
glycerophospholipids
Structures of
glycerophospholipids
Prentice Hall c2002
Phosphatidylserine (PS)
Chapter 9
15
Cardiolipin:
• Two molecules of PA esterified through their
phosphate groups to an additional molecule
of glycerol is called cardiolipin
Importance of cardiolipin
 Cardiolipin is found in bacteria and eukaryotes
(inner mitochondrial membrane)
 Cardiolipin is antigenic, and is recognized by
antibodies raised against Treponema pallidum,
the bacterium that causes syphilis
Sphingolipids
• Sphingolipids - sphingosine is the backbone. Abundant in
central nervous system tissues
• Ceramides - fatty acyl group linked to sphingosine
• Sphingomyelins - phosphocholine attached to ceramide
• Cerebrosides - glycosphingolipids with one monosaccharide
residue attached to ceramide
• Galactosylcerebrosides - a single b-D-galactose as a polar
head group
• Gangliosides - contain oligosaccharide chains with Nacetyl-neuraminic acid (NeuNAc) attached to a ceramide
Prentice Hall c2002
Chapter 9
18
(a) Sphingosine
(b) Ceramides
Prentice Hall c2002
Chapter 9
19
Significance of Ceramide & sphingosine
• Ceramide
– A long-chain fatty acid is attached to the amino
group of sphingosine through an amide linkage
• Ceramides appear to be involved in the
response to stress
• sphingosine inhibits protein kinase C
Sphingomyelin
• Amino alcohol sphingosine, rather than
glycerol
• The alcohol group at carbon 1 of sphingosine
is esterified to phosphorylcholine
• Sphingomyelin is an important constituent of
the myelin of nerve fibers
Sphingomyelin degradation
• Sphingomyelin is degraded
in lysosomes by
sphingomyelinase to give
ceramide,
• and ceramidase to give
sphingosine
• Niemann-Pick disease is
due to sphingomyelinase
deficiency
Glycolipids
• Also known as glycosphingolipids
• contain both carbohydrate and lipid
components
• Ceramides plus a long-chain fatty acid
attached to the amino alcohol sphingosine
 essential components of:
 All membranes
 Nerve cells
Glycolipids Significance
 Glycosphingolipids are antigenic  a source of blood
group antigens
 The carbohydrate portion of a glycolipid is the
antigenic determinant
 serve as cell surface receptors for cholera and tetanus
toxins
• Structure of a galactocerebroside
• Galactocerebroside—the most common
cerebroside found in membranes
• Glucocerebroside
Prentice Hall c2002
Chapter 9
26
Location
• cerebrosides predominantly in the brain and
peripheral nervous tissue
Ganglioside (sphingolipid)
• found in the ganglion cells
• Derivatives of ceramide oligosaccharides, and
contain one or more molecules of NANA.
• negatively charged at physiologic pH 
provided by N-acetylneuraminic acid (NANA).
• [NANA is also referred to as sialic acid.]
•