guts session on carbohydrates and glycolipids dr. arrel toews (say tavz, like “waves”) 420 me...
TRANSCRIPT
GUTS session on carbohydrates and glycolipids
Dr. Arrel Toews (say Tavz, like “waves”)
420 ME Jones Building
843-8727
A primer on carbohydrate and glycolipid structure, nomenclature, properties, and general functions
See also the GUTS carbohydrate/glycolipid notes (.doc) - self-assessment exam - additional information
OXIDATION STATES OF CARBON: You better know!!
oxidation
OXIDATION: - loss of e-
- loss of H - gain of O
reduction
REDUCTION: (just the opposite) - gain of e-
- gain of H - loss of O
saturated alcohol aldehyde ketone carboxylic carbonhydrocarbon acid dioxide
H H O O Ol l ll ll ll
R-C-H R-C-OH R-C-H R-C-R R-C-OH O=C=Ol l H H
carbohydrates
fats
SUGARS – CARBOHYDRATES - “hydrates of carbon”
Sugars - polyalcohols (-OH) + aldehyde = aldoseor + ketone = ketose
Simple sugars – monosaccharides2 sugars – disaccharidessugar polymers - polysaccharides
Need for: - energy fuel - energy storage - cell membranes/walls - cell-cell interactions
General formula: (CH2O)n
H—
H2
ClClC
—OH
—OH
H Ol aldehydegroup
Glyceraldehyde(an aldose)
C —OH lClC
O
—OH
H2
H2
ketonegroup
Dihydroxyacetone(a ketose)
H—
H2
ClClC
—OH
—OH
H Ol aldehydegroup
H—
H2
lClC
—OH
—OH
aldehydegroup
ald
C —OH lClC
O
—OHH2
H2
ketonegroup
C —OH lClC
O
—OHH2
H2
ketonegroup
)
Fischer projection
OH
H-C l H-C-OH lHO-C-H l H-C-OH l C l CH2OH
O
1
6
5
4
3
2
C1
Open-chainstructure
O
H-C l H-C-OH lHO-C-H l H-C-OH l H- C-OH l CH2OH
1
6
5
4
3
2
Various ways to visualize the structure of glucose
H
OHH
OH
H
HO
HOCH2
HOH
H
O
1
6
5
4
3 2
Ring structure(Haworth projection)
Shorthand method of drawing sugar structures
(l = OH; C & H understood)
OOCH2OH
Space-filling model
Constantly opening/closing but prefers ring
=
=
C1-OH
Glucose(open-chain form)
- OH on C5 links to C1 (aldehyde C)
- C1 changes from aldehyde to alcohol
- 6-sided (5-C, 1-O) ring forms
This is important for glycosidic links (hooking sugars together)
Glucose likes to form a ring in solution
-glucose
-glucose
O
H-C l H-C-OH lHO-C-H l H-C-OH l H- C-OH l CH2OH
1
6
5
4
3
2
H
OH
H
HO
HOCH2
HOH
H
6
5
4
3 2
OH HC O
1
OH
H
OH
H
H
HO
HOCH2
HOH
H
O
1
6
5
4
3 2
H
OHH
OH
H
HO
HOCH2
HOH
H
O
1
6
5
4
3 2
fructose
- OH on C5 links to C2 (ketone C)
- C2 changes from ketone to alcohol
- 5-sided (4-C, 1-O) ring forms
Fructose likes to form a ring too!!
=
=
C2-OH
-fructose(ring form)
H2-C-OH l C O lHO-C-H l H-C-OH l H- C-OH l CH2OH
1
6
5
4
3
2
2
CH2OH lC
OH
HOCH2
OH
5OH
H
H
HO
Constantly opening/closing but prefers ring
HHO
HOCH2
OH
5
CH2OH
OH
2O
H
H
sugar + ATP sugar~P + ADP
- Sugar~P are “primed for metabolism” – extra energy
- Key intermediates in: - energy production - biosynthesis
Phosphorylated sugars are “activated intermediates”
dihydroxyacetone-P glyceraldehyde-P glucose-6-P
kinase
O-
l-O-P O l O l CH2
H
OHH
OH
H
HO
HOH
H
O6
O-
l-O-P O l O l CH2
lH-C-OH l CH O
O-
l-O-P O l O l CH2
l C O l CH2OH
N-glycosidic links (C-N bonds) are important too
Adenosine(the A in ATP)
Ribose
D-glucosamine(an amino-sugar)
H
OH
H
H
HO
HOCH2
HOH
H
O
NH3+
H
OH
HOCH2
H
O1
54
2
H
OHH
OH
H
H
HOCH2
H
O H
OHH
OH
D-ribose(ATP, RNA)
2-deoxyribose(DNA)
Important pentoses
3
2
H
OH
HOCH2
H
O
HH
OH
NH2
C NN C
HC CN N
CHAdenine
Disaccharides – 2 sugars joined by glycosidic link
H
OHH
OH
H
HO
HOCH2
HOH
H
H
OHH
H
HO
HOCH2
HOH
1
6
5
4
3 2
C1
H
OHH
H
HO
HOCH2
HOH
H
1
6
5
4
3 2
-glucose glucose
OH
OO
HOH
hydrolysis
Hydrolysis (breaking a bond by addingwater across it) of glycosidic links regenerates sugar monomers
Formation of a glycosidic link locks C1 intospecific configuration (either or ).It CANNOT open or close anymore!!
This matters a lot,especially for di/polysaccharides
Maltoseglucose(-1,4)glucose
H
H
OH
H
HO
HOCH2
HOH
H
H
H
H
HOCH2
HOH
1
6
5
4
3 2
H
OHH
OH
H
HOCH2
HOH
H
1
6
5
4
3 2
H
H
H
HOCH2
HOH
14
3 2O
HOH
condensation
Glycosidic links between sugar monomersare formed by condensation (dehydration)reactions
O O
Disaccharides – 2 sugars joined by glycosidic link
Sucrose(fruit sugar)
glucose + fructose
Cellobioseglucose(14)glucose
-glycosidic link (C1-OH is )
OH
HH
H
HO
HOCH2
HOH
H
O
1
OH
H
OH
H
H
HOCH2
HOH
H
O
14O
Lactose (milk sugar)galactose(14)glucose
-glycosidic link
H
OH
HOCH2
HOH
H
H
HOCH2
HOH
1
6
5
43 2
H
OHH
OH
H
HOCH2
HOH
H
1
6
5
3 2
H
H
H
HOCH2
HOH
14
3 2
OHO
HH
O O
Important glucose polymers
AMYLOSE (starch in plants) long linear chains
(14 links in chains with 16 links at branches)
AMYLOPECTIN (starch in plants) & GLYCOGEN (animals) branched chains
1 4
1
6
1 4
(14 links)
1 4
(14 links)
CELLULOSE (in plants) long linear chains
1 4
Glycosaminoglycans (GAGs)
aka mucopolysaccharides
long chains of disaccharide-repeat units - acidic sugar (- charge) - acetylated amino sugar (no charge)
Important components of: - extracellular matrix - synovial fluid of joints - mucus - vitreous humor of eye
Proteoglycans – proteins with lots of GAG chains attached
Glucuronate N-acetyl- (acidic) glucosamine
Repeating disaccharides in hyaluronic acid
OCOO-
OH
OHO O
O
CH2OH
NH-C-CH3 ll O
HO
.............
An example of glycosaminoglycan (GAG) repeat unitsDon’t worry about the structures; just note the (-) charge
(repeat)(repeat)
Acetylation of NH2 group (otherwise present as NH3+)
prevents protonation, so no (+) charge present
Other GAGs have even more (-) charges!
OCOO-
OH
OHO O
O
CH2OH
NH-C-CH3 ll O
HO
............. (repeat)(repeat)
Sulfate (SO4=) groups on various –OH (and to variable degrees)
in other GAGs. Sulfation makes them even more negative
SO4=
SO4=SO4
=
GLY
CERO
LFATTY ACID
FATTY ACID
P
chol
ine
polar head long hydrophobic tail
GLY
CERO
LFATTY ACID
FATTY ACID
P
chol
ine
chol
ine
polar head long hydrophobic tail
Structures and properties are generally similar to phospholipids (amphipathic)
Phospholipids
Sphingolipids
F A T T Y A C I D
O
(usually)
Long-chain amino alcohol (sphingosine)sugar(s)
polar head long hydrophobic tail
Remember Sphingolipids??
(Glyco)
base molecule is sphingosine (in black above)long-chain fatty acid (several different ones)
O
NH
CF A T T Y A C I D
X
O
OHA primer on sphingolipid nomenclature
(trans)S p h i n g o s i n e
if X = H, the molecule is ceramide (base of all sphingolipids)
if X = galactose, the molecule is cerebroside (galactosyl-ceramide, an important myelin lipid)if X = galactose-sulfate, the molecule is sulfatide (also a myelin component)if X = glucose, the molecule is glucosyl-ceramide
(precursor to gangliosides, globosides)
if X = P -choline, the molecule is sphingomyelin
Vocabulary – do you know the meaning of the following terms?
oxidation vs reductionsugarsmono-, di-, and polysaccharidesglucosefructoselactosesucroseglycogenstarch (amylose and amylopectin)glycosaminoglycan (mucopolysaccharide)proteoglycansphingolipidsphingosineceramidesphingomyelincerebroside (and sulfatide)