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Carbohydrates (22.1-22.3)

Primary source of energy in body
Monosaccharides
“Simple sugars” - Cn(H2O)n - hydrates of carbon
n=6 C6(H2O)6 -- C6H12O6
n=4 C4(H2O)4 -- C4H8O4
have between 3-7 carbons
every carbon has a hydroxyl group except one - one is an aldehyde or ketone
O
O
H C R
family name ends in “ose”
Carbohydrates are chiral molecules
carbon must have 4 different groups
chiral molecule must have no plane of symmetry
Stereoisomers
enantiomers
O
O
C
C
H
OH
HO
H
H
OH
HO
H
CH2OH
mirror
CH2OH
non-mirror images
H
H
D vs L
nature uses
D form
C R
diastereomers
non-superimposable mirror images
H
R'
O
O
C
H
C
H
OH
HO
H
OH
H
CH2OH
H
OH
CH2OH
1
Classification of Monosaccharides
By functional group
aldose
aldehyde
ketose
ketone
H
CH2OH
O
C
H
HO
C O
OH
HO
H
H
H
OH
H
OH
H
OH
H
OH
By # carbons in sugar
triose
3 carbon
pentose
5 carbon
C O
CH2OH
O
H
CH2OH
hexose
6 carbon
C
C
HO
H
HO
H
OH
H
CH2OH
CH2OH
O
H
HO
H
H
OH
HO
H
H
OH
CH2OH
CH2OH
By functional group and # carbons in sugar
Ex: aldohexose
Ex: ketotriose
2
Fischer Projections of Aldohexoses
straight line drawing of monosaccharides (also called open chain form)
recall that where line crosses, there is a carbon - it is a chiral carbon in Fischer proj.
Aldohexoses - aldehyde functional group
6 carbons
penultimate carbon - second to last carbon - carbon 5 in aldohexoses
There are 8 different aldohexoses (actually 16 including their mirror images)
What stays the same between aldohexoses?
Horizontal bonds come
out of the paper
towards you
Vertical bonds go into
the paper away from
you
H 1 O
C
Penultimate carbon
4
If OH on left - L
Carbon #1 is always aldehyde
#5 determines D or L - always D in nature
#6 is CH2OH
2
3
H
5
6
Where OH is on 2,3,4 determines the name of sugar
OH
If OH on right - D - again, nature uses D form
CH2OH
3
There are 8 unique aldohexoses (don’t forget each one has a mirror image also)
H
O
H
C
O
H
C
O
H
C
OH
HO
H
OH
H
OH
HO
H
OH
H
OH
H
OH
HO
H
OH
H
OH
H
OH
H
D-Allose
H
O
H
C
H
CH2OH
H
CH2OH
D-Altrose
H
C
O
H
HO
HO
H
H
H
OH
HO
H
OH
H
CH2OH
D-Mannose
H
OH
H
H
OH
D-Glucose
C
HO
OH
CH2OH
H
O
H
H
OH
CH2OH
D-Gulcose
H
C
H
O
O
C
OH
HO
H
OH
HO
H
HO
H
H
HO
H
HO
H
OH
CH2OH
D-Idose
H
OH
CH2OH
D-Galactose
H
OH
CH2OH
D-Talose
4
Predominant structural form of Aldohexoses
Sugars are not predominantly in the open chain form
A hydroxyl group attaches the partially positive carbon of the carbonyl to form
a hemiacetal leaving a cyclic structure
O H
H
O
General reaction
+
R C O R'
forming a hemiacetal
O R'
R C H
H
In sugars the aldehyde
and alcohol are part of the
same sugar leaving a
cyclic molecule:
Carbon has 4 bonds
d-
H
HO
H
H
H
HO
O
H
d+ C
H
H C OH
OH
OH
CH2OH
D-glucose
H
O
OH
H
OH
H
D-gulcose
OH
Oxygen connects
carbons 1 and 5
when starting
with an aldose
CH2OH
or
HO C H
H
HO
H
OH
H
OH
O
D-Idose
H
CH2OH
5
Why does the OH on carbon 5 attack the carbonyl instead of the OH on carbons 4 or 6?
d-
H
O
d+ C
H
HO
OH
H
H
OH
H
OH
CH2OH
1. Carbon 5 instead of 6 because:
a secondary alcohol is more reactive than a
primary alcohol b/c of inductive effects from
the carbons
carbons are electron donating which makes
the oxygen more electronegative. The more
carbons, the more donation, the more
reactive the oxygen.
2. Carbon 5 instead of 4 because:
A six membered ring is most stable ring size
b/c it allows the bond angle closest to the
109.5 ideal angle of a tetrahedron.
If carbon 4 is used, a 5 membered ring is
formed which is stable but not as stable as a
six-membered ring. Carbon 3 or 2 would be
even more strained and does not happen.
6
Haworth structures of aldohexoses
more realistic representation of cyclic structure
H
C
1
H C OH
2
H
H
4
H
O
OH
5
H
H
OH
3
HO
6 CH2OH
D-glucose
closed chain
O
HO C H
OH
HO
H
H
OH
HO
H
OH
H
H
OH
H
H
O
OH
CH2OH
CH2OH
D-glucose
closed chain
D-glucose
open chain
Carbon 6 goes “above” ring in D form of sugar
CH2OH
5
4
O
If OH is on left in Fischer
it points upward in Haworth
1
OH
HO
OH
3
a-D-glucose
6
If OH is on right in Fischer
it points downward in Haworth
6
2
OH
The hemiacetal carbon
is called the anomeric carbon
If OH is on opposite side
of ring of carbon 6, sugar
is in alpha form
CH2OH
5
4
O
1
OH
HO
3
OH
2
OH
b-D-glucose
OH on same
side as C 6,
sugar in beta
form7
Convert between Fischer and Haworth projections for the following structures
H
O
H
C
O
C
H
OH
HO
H
OH
H
OH
H
OH
H
OH
H
OH
H
OH
CH2OH
CH2OH
b-D-Allose
D-Allose
H
H
H
O
C
a-D-Altrose
D-Altrose
O
C
CH2OH
CH2OH
O
O
HO
OH
HO
OH
CH2OH
OH
OH
a-D-Gulose
OH
CH2OH
b-D-Mannose 8
OH
Fischer Projections of ketohexoses
ketohexoses - ketone functional group
6 carbons
penultimate carbon - second to last carbon - carbon 5 in ketohexoses
There are 4 different ketohexoses (actually 8 including their mirror images)
What stays the same between ketohexoses?
Carbon #2 is always ketone group
#1 is always CH2OH
#5 determines D or L - always D in nature
#6 is CH2OH
1
CH2OH
2
C O
Still penultimate carbon
3
Where OH is on 3,4 determines the name of sugar
4
If OH on left - L
H
5
6
OH
If OH on right - D - again, nature uses D form
CH2OH
9
There are 4 unique ketohexoses (don’t forget each one has a mirror image also)
CH2OH
CH2OH
CH2OH
CH2OH
C O
C O
C O
C O
H
OH
HO
H
OH
H
OH
HO
H
OH
H
OH
H
CH2OH
D-Psicose
H
CH2OH
D-Fructose
H
OH
HO
H
H
HO
H
OH
CH2OH
D-Sorbose
H
OH
CH2OH
D-Tagatose
Draw using Fischer projections and name the L forms of Fructose and Sorbose
10
Haworth structures of ketohexoses
Sugars are predominantly in cyclic form like with aldohexoses
Again, a hydroxyl group attaches the partially positive carbon of the carbonyl to
form a hemiacetal
But, ketohexoses form both 6 and 5 membered rings - 5 membered rings predominate
Form 5 membered ring because carbon 5 OH (a secondary alcohol) is more
reactive than carbon 6 OH (a primary alcohol). But, in ketohexoses, OH on
carbon six is also used b/c a six membered ring is formed with OH on carbon 6
It’s a competition between a five membered ring formed by a secondary alcohol
versus a 6 membered ring formed by a primary alcohol. Secondary alcohol
forming a 5 membered ring wins most of the time.
6
1
2
HO
H
H
CH2OH
3
4
5
4
OH
or
6
6
CH2OH
D-Fructose
CH2OH
a-D-fructose
2
OH
3
OH
H
OH
OH
5
C O
1
CH2OH O
Oxygen connects
carbons 2 and 5
when starting
with an ketose
CH2OH O
The hemiacetal carbon
is called the anomeric carbon
1
OH
5
4
3
OH
OH
2
b-D-fructose
CH2OH
11
Convert between Fischer and 5 membered ring Haworth projections for the following structures
CH2OH
CH2OH
C O
C O
H
OH
HO
H
H
OH
HO
H
H
OH
H
CH2OH
CH2OH
b-D-Psicose
D-Psicose
D-Tagatose
a-D-Tagatose
Draw the Haworth projection for a-L-fructose
CH2OH
C O
OH
CH2OH
CH2OH
O
OH
OH
OH
CH2OH
a-D-Sorbose
12
Important monosaccharides (22.5)
Glucose - also known as dextrose
most important simple carbohydrate in human metabolism
starting point of glycolysis, TCA, eletron transport chain
maintenance is critical in diabetics. Insulin and glucagon regulate blood levels.
Body converts other sugars to glucose for use in metabolism
Galactose - found in plant gums and pectins
galactosemias - genetic disorders in which galactose cannot be metabolized b/c
of missing enzymes
galactose builds up in blood and tissues
initial symptoms include vomiting, enlarged liver, failure to thrive
can also cause liver failure, mental retardation, and cataracts
fructose - also known as levulose or fruit sugar
found in honey and fruits - twice as sweet as sucrose so is often
used as a sweetner in beverages and prepared foods.
Ribose and deoxyribose - aldopentoses
sugars in nucleotides
HO CH2
OH
O
OH
OH
HO CH2
O
OH
OH
13
Disaccharides (Section 22.7)

2 monosaccharides connected through a glycosidic bond between carbon 1 of one
monosaccharide and carbon 4 of the second
results in loss of H2O
An a-1,4 link
6
CH2OH
5
O
4
3
2
6
CH2OH
5
O
1
1
4
o
2
3
The hemiacetal carbon
becomes an acetal carbon
A b-1,4 link
Acetal carbon is in alpha
position therefore it is
an alpha linkage
6
CH2OH
5
O
4
6
CH2OH
5
O
4
o
1
3
2
1
3
2
Acetal carbon is
in beta position
14
Important disaccharides
Maltose - malt sugar - used in prepared foods as a sweetner
2 a-D-glucose molecules joined by an alpha 1,4 link
CH2OH
O
OH
a-D-glucose
1
4
CH2OH
O
OH
a-D-glucose
o
OH
OH
OH
OH
Lactose - milk sugar - major carbohydrate in mammalian milk
b-D-galactose and b-D-glucose molecules joined by a beta 1,4 link
CH2OH
O
OH
OH
b-D-galactose
o
CH2OH
O
OH
OH
b-D-glucose
OH
OH
lactose intolerance - common in adults - results from lack of lactase
- bacteria in intestines convert lactose to lactate, CO2, H2, and methane
- result is bloating, cramps, flatulence and diarrhea
15
Sucrose - table sugar - sugar cane and sugar beets most common sources
a-D-glucose and b-D-fructose molecules joined by a 1,2 anomeric link
CH2OH
O
OH
1
2
a-D-glucose
OH
CH2OH O
OH
O
HO
2
1,2 anomeric link
CH2OH
OH
1
b-D-fructose
hydrolysis of sucrose yields 1 molecule of glucose and 1 molecules of fructose
this mixture - called invert sugar - is sweeter than sucrose itself
16

Polysaccharides (Section 22.9)
polymers of monosaccharides - range from tens to many thousands monomers
homopolysaccharide - consists of only 1 type of monosaccharide
heteropolysaccharide - more than one type of monosaccharide
monosaccharides are connected by 1,4 linkages
Some important disaccharides
Cellulose - straight chain homopolysaccharide of >3,000 b-D-glucose
connected by b-1,4 links
basic structural unit of plant cell walls - comprises 33% of vegetable matter
6
4
CH2OH
5
O
OH
3
2
OH
90% of cotton is cellulose/50% of paper
OH
3
1
o
4
2
OH
5
O
6 CH2OH
Cellulose repeating unit
1
O
Each glucose unit is ‘turned over’
relative to the one before it but
each glucose is still the b anomer
17
Chair Conformation of six membered rings
Haworth projections are not 100% accurate in displaying cyclic structures - in reality,
the ring is bent up at one end and down at the other b/c of tetrahedral bonding
H OH
H OH
6
4
HO
HO
5
3
H
H
6
4
H O
1
2
OH
OH
H
b-D-glucose
C-6 group and C-1 OH on same sides
HO
HO
5
3
H
H
H O
1
2
H
OH
OH
a-D-glucose
C-6 group and C-1 OH on opposite sides
Repeating unit of cellulose
18
Cellulose continued
Each OH group can hydrogen bond to two other OH groups
Very large and extensive H-bonding network - makes cellulose very rigid and linear
Chain 1
Chain 2
Why does paper get “weaker” when wet? How do paper towels absorb water?
19
Starch - homopolysaccharide of a-D-glucose
connected by a-1,4 links
storage form of glucose in plant cells for use later in energy production
2 types of Starch
1. Amylose - linear polymer of glucose with a-1,4 links
2. Amylopectin - branched-chain polymer - main chain of glucose linked by a-1,4 links
shorter chains branched off main chain by a-1,6 links
amylase - enzymes that break the a-1,4 links in starch
20
Glycogen - highly branched homopolysaccharide of a-D-glucose
main chain connected by a-1,4 links
branches by a-1,6 links
same as amylopectin form of starch but glycogen is more highly branched
glycogen branches about every 10 glucoses but amylopectin every 25
storage form of glucose in animals for use later
largest reserves found in liver and muscle
21

Glycoproteins (application on page 654)
Proteins that contain carbohydrates in addition to the amino acid portion of the protein
carbohydrates covalently attached to OH of Ser or Thr, or NH2 group of Asn
Examples:
antibodies
ABO blood proteins
22
Lipids (Chapter 24)
Classified by solubility in non-polar solvents, not by chemical structure
3 main functions are energy storage, cell membranes, chemical messengers

Lipids are structurally diverse
they are not polymers of monomeric units like proteins, NA, and polysaccharides
Types of lipids
fats, oils, waxes, cholesterol, most steroids, phospholipids, prostaglandins
O
O
C OH
O
H3C(H2C)28H2C O C
CH3
(CH2)14CH3
A wax
HO
OH
O
H2C O C
A prostaglandin
(CH2)14CH3
H3 C
O
HC O C
(CH2)7CH CH(CH2)7CH3
O
H2C O C
CH3
CH3
(CH2)16CH3
A triacylglycerol
CH3
CH3
Cholesterol, a steroid
23
HO

Storage Lipids (triacylglycerides and waxes)
Characteristics of triacylglycerides:
1) store energy - fats and oils give 9 kcal of energy/g - carbs and proteins give 4 kcal/g
2) stored in adipocytes which are the cells that constitute adipose tissue
3) dietary lipids come from vegetable oils, dairy products and animal fat
4) lipids are esters of fatty acids and glycerol
Formation of Ester
alcohol
+
Carboxylic acid
O
Ester
O
HO C R'
R OH
R O C R'
+
Formation of Triacylglycerides (triesters)
R=12 - 24 carbons long
H2C OH
HC OH
H2C OH
Glycerol
polyalcohol
HOH
O
H2C O C
+
O
3 R'
C OH
(CH2)14CH3
O
HC O C
(CH2)7CH CH(CH2)7CH3
O
Fatty acids
H2C O C
(CH2)16CH3
Triacylglyceride
(or triglyceride)
24
Storage lipids are derivatives of fatty acids
fatty acid - hydrocarbon chains of 4 to 36 carbons with a carboxylic acid functional group
12-24 carbons most common
usually even numbers of carbons b/c of synthesis from acetate units
very hydrophobic
dissolve easily in organic solvents like acetone but immiscible in water
25
Types of fatty acids
saturated fatty acids
no C-C double bonds
fully saturated with hydrogen
“animal fats”
unsaturated fatty acids
contain C-C double bond(s)
Monosaturated
only 1 dbl bond
Polysaturated
>1 dbl bond
cis
H
H
C C
R
Naturally occurring
fatty acids
“plant oils”
R'
or
trans
H
R'
C C
R
H
Industry produced from
naturally occurring 26
Some naturally occuring fatty acids
Systematic name
Common Name
Structure
Abbreviation
n-Dodecanoic acid
Lauric acid
CH3(CH2)10COOH
12:0
n-Tetradecanoic acid
Myristic acid
CH3(CH2)12COOH
14:0
n-Hexadecanoic acid
Palmitic acid
CH3(CH2)14COOH
16:0
n-Octadecanoic acid
Stearic acid
CH3(CH2)16COOH
18:0
n-Eicosanoic acid
Arachidic acid
CH3(CH2)18COOH
20:0
Palmitoleic acid
CH3(CH2)5CH=CH(CH2)7COOH
16:1(D )
Oleic acid
CH3(CH2)7CH=CH(CH2)7COOH
18:1(D )
a-Linoleic acid
CH3(CH2)4CH=CHCH2CH=CH(CH)7COOH
18:2(D
9,12
Linolenic acid
CH3CH2CH=CHCH2CH=CHCH2CH=CH(CH2)7COOH
18:3(D
9,12,15
Arachidonic acid
CH3(CH2)4CH=CHCH2CH=CHCH2CH=CHCH2CH=CH(CH2)3COOH
20:4(D
5,8,11,14
9
9
)
)
Fatty Acid Abbreviations
Always start # on COOH
Number of carbons: number of dbl bonds (D dbl bond positions)
Example:
16:0
16
- fatty acid w/ 16 carbons H3C
no double bonds
H2
C
15
14
C
H2
H2
C
13
12
C
H2
H2
C
11
10
C
H2
H2
C
9
8
C
H2
H2
C
7
6
C
H2
H2
C
5
4
C
H2
H2
C
3
O
2
C
C 1 OH
H2 27
)
M
P
Draw the following:
14:0 - fatty acid with 14 carbons and no double bonds
18:1(D9)
- fatty acid with 18 carbons and one double bond beginning on carbon 9
begin labeling at COOH end
H
Start off double
bond cis and
then finish
molecule
12
14
16
18
15
17
10
11
13
H
7
9
5
8
3
6
O
4
2
1
OH
Draw 16:1(D9)-trans
28
Common Name Abbreviation
Lauric acid
Myristic acid
Palmitic acid
Stearic acid
Arachidic acid
Lignoceric acid
12:0
14:0
16:0
18:0
20:0
24:0
Palmitoleic acid
16:1(D )
Oleic acid
18:1(D )
Melting Point (C)
44.2
56.9
63.1
69.5
76.5
86
9
-0.5
9
13.4
a-Linoleic acid
18:2(D
Linolenic acid
Arachidonic acid
18:3(D
)
5,8,11,14
20:4(D
)
9,12
)
9,12,15
-5
-11
-49.5
Solid at
r.t. –
animal
fats
liquid at
r.t. –
vegetabl
e oils
Melting point increases as:
1) Size increases
compare first 5 fatty acids
2) Degree of saturation increases
compare 18:0, 18:1, 18:2, 18:3 - biggest drop is from 0 dbl bonds to 1 dbl bond
makes sat. fats solid at r.t. and unsat. fats liquid at r.t.
29
linoleic acid, 18:2
Stearic acid, 18:0
Triglyceride with saturated fats
Triglyceride with unsaturated fats
30
Unsaturated Fatty
Acids (%)
Saturated Fatty Acids (%)
Source
C12
Lauric
C14
Myristic
C16
Palmitic
C18
Stearic
C18
Oleic
C18
Linoleic
--2
1
1
10
3
25
25
25
15
10
8
50
25
46
6
5
10
---------
1
1
-----
8
5
7
7
4
5
5
4
46
83
60
34
42
7
20
53
Animal Fat
Lard
Butter
Human Fat
Vegetable Oil
Corn
Olive
Peanut
Soybean
Lipids from vegetables contain mainly unsaturated fats so are liquid at room temp
Lipids from animals contain much more saturated fats so are solids at room temp
31