Transcript Slide 1

Carbohydrates of Physiologic
Significance
CARBOHYDRATES ARE ALDEHYDE OR KETONE DERIVATIVES OF
POLYHYDRIC ALCOHOLS
(1) Monosaccharides are those carbohydrates that cannot be hydrolyzed into simpler
carbohydrates: They may be classified as trioses, tetroses, pentoses, hexoses, or heptoses,
depending upon the number of carbon atoms; and as aldoses or ketoses depending upon
whether they have an aldehyde or ketone group. Examples are listed in Table 13–1.
(2) Disaccharides are condensation products of two monosaccharide units. Examples are
maltose and sucrose.
(3) Oligosaccharides are condensation products of two to ten monosaccharides; maltotriose*
is an example.
(4) Polysaccharides are condensation products of more than ten monosaccharide units;
examples are the starches and dextrins, which may be linear or branched
polymers. Polysaccharides are sometimes classified as hexosans or pentosans, depending upon
the identity of the constituent monosaccharides
Anomers
Epimerisation
Important Disaccharides
starch
Glycosaminoglycans (mucopolysaccharides) are complex carbohydrates
characterized by their content of amino sugars and uronic acids.
When these chains are attached to a protein molecule, the result is a
proteoglycan.
Proteoglycans provide the ground or packing substance of connective tissues.
Structure of proteoglycan
from cartilage
Structures of A, B,and O
oligosaccharide antigen
Carbohydrates Can Be Linked to Proteins Through
Asparagine (N-Linked) or Through Serine or Threonine (OLinked) Residues
What are these moleculs ?
What are these moleculs?
Lipids of Physiologic Significance
(1) relatively insoluble in water and
(2) soluble in nonpolar solvents such as ether
and chloroform.
LIPIDS ARE CLASSIFIED AS SIMPLE
OR COMPLEX
Fatty Acids Are Named After Corresponding
Hydrocarbons
Saturated Fatty Acids Contain No Double
Bonds
Unsaturated Fatty Acids Contain One or
More Double Bonds
Fatty acids may be further subdivided as follows:
(1) Monounsaturated (monoethenoid, monoenoic) acids, containing one
double bond.
(2) Polyunsaturated (polyethenoid, polyenoic) acids, containing two or more
double bonds.
(3) Eicosanoids: These compounds, derived from eicosa- (20-carbon)
polyenoic fatty acids, comprise the prostanoids, leukotrienes (LTs), and
lipoxins (LXs). Prostanoids include prostaglandins (PGs), prostacyclins
(PGIs), and thromboxanes (TXs).
The General Structure of Fatty Acids

The general structure of a fatty acid is a
long hydrocarbon chain with a carboxyl
group on carbon 1 (C1).
A fatty acid (Palmitate 16:0)
Hydrophilic carboxylate head
Hydrophobic hydrocarbon tail
Space Filled Models of FFAs
Common unsaturated fatty acids
w-3 (n-3) unsaturated fatty
acids
ALA 18:3 (all cis) D9,12,15 alpha-linolenic acids
EPA 20:5 (all cis) D5,8,11,14,17
DHA 22:6 (all cis) D4,7,10,13,16,19
BIOACTIVE LIPIDS: MEMBRANE SPHINGOLIPIDS
and GANGLIOSIDES
Triacylglycerides and
Phospholipids
Choline head-group
Polar
Saturated fatty acid
( sn-1 position)
Unsaturated fatty acid
(sn-2 position)
Phosphatidylcholine
Nonpolar
Differences in the
length and degree of
saturation of fatty
acids affect their
ability to pack
& hence the fluidity
of the bilayer
Phospholipid Structure
CH2
+
N(CH )
3 3
Choline
CH2
O
O
P
O–
Phosphate
O
CH2
CH
O
O
C
O C
CH2
Glycerol
O
Fatty acids
Hydrophilic
head
Hydrophobic
tails
(a) Structural formula
(b) Space-filling model
(c) Phospholipid
symbol
The Lipid Bilayer
Hydrophilic heads
Hydrophobic tails
bilayer
Hydrophilic heads
Head (hydrophilic)
Tails (hydrophobic)
Lipid Bilayer (Double Membrane)
WATER
Hydrophilic
head
Hydrophobic tail
WATER
The phospholipid bilayer is the basic structures of biomembranes
What is this phospholipids
name?
a
s
O
Phosphatidyl
inositol signal
cascades may
lead to release
of
arachidonate.
O
R1
C
H2C
O
O
C
CH
H2C
cleavage by
Phospholipase C
R2
O
O
P
O
O
H
OPO32
OH
H
OH
PIP2
H
H
phosphatidylinositol4,5-bisphosphate
OH
H
H
OPO32
After PI is phosphorylated to PIP2, cleavage via
Phospholipase C yields diacylglycerol (and IP3).
plasmalogens
Sphingosine
Structure of a ceramide (N-acylsphingosine)
Structure of sphingomyelin
Four major phospholipids in mammalian cell membranes
(or galactosylceramide)
Structures of
common
sphingolipids:
Gangliosides are
just cerebrosides
with NANA (sialic
acid) attached!
Gangliosides
•Gangliosides are the most complex sphingolipids.
•These are carbohydrate-rich sphingolipids that contain at least one acidic sugar.
•Ganliosides are synthesized by the ordered, step-wise addition of sugar residues
to ceramide.
•Synthesis of these complex lipids requires activated sugars (e.g. UDP-glucose,
•UDP-galactose, UDP-N-acetylneuraminate…)
•This is just one example, more than 60 different gangliosides have been characterized.
glucose (Glc), galactose (Gal), N-acetylgalactosamine (GalNAc), N-Acetylneuraminate (NAN)
What is these ?
EICOSANOIDS ARE 20-CARBON LIPIDS THAT
ACT LOCALLY TO STIMULATE A VARIETY OF
PROCESSES
O
CO2CH3
OH
OH
Prostaglandins:
act through cAMP to stimulate contraction of
smooth muscle, affect blood flow, elevate body
temperature, or cause inflamation & pain
Prostaglandin E1
CO2O
O
CH3
OH
Thromboxane A2
O
CO2CH3
Thromboxanes:
produced by platelets; act in formation of blood
clots & reduction of blood flow at the site of a clot
Leukotrienes:
induce contraction of muscle lining
airways to the lungs.
Leukotriene A4
I won’t expect you to remember these structures.
MAMMALIAN CELLS
SYNTHESIZE EICOSANOIDS
FROM ARACHIDONIC ACID
Arachidonic acid is released by
breakdown of phospholipids in
response to cell damage or
hormonal stimuli.
phospholipids containing arachidonic acid
phospholipase A2
H2O
lysophospholipid
CO2-
stimulus
2 O2
cyclooxygenase
aspirin,
ibuprofin
Mammals have two isozymes of
cyclooxygenase -- COX-1 & COX-2. The
prostaglandins produced by COX-1
participate in “house-keeping” functions
such as secretion of gastric mucin;
those produced by COX-2 play roles in
inflamation.
Aspirin, ibuprofin and acetaminophen
(nonsteroidal anti-inflamatory drugs,
NSAIDS) block prostaglandin synthesis
by inhibiting cyclooxygenase.
arachidonate
(20:4)
X
O
CO2-
O
OOH
prostaglandin G2
cyclooxygenase
O
CO2-
O
OH
prostaglandin H2
other eicosanoids
Size and Compositions of the Lipoproteins
Protein
Phospholipid
Cholesterol
Triglyceride
100
Chylomicron
80
VLDL
Percent
LDL
Protein
60
40
Cholesterol
20
HDL
0
Phospholipid
Triglyceride
Chylomicron VLDL
LDL
HDL
Figure 5-18 Page 155
PON & CAD Status
LDL
Up-regulated
by light ethanol
HDL-PON
OX-LDL
Inactive
products
Plaque
Down-regulated
by heavy ethanol
Foam Cell
Macrophage