Transcript anomeric carbon

1
anomeric
carbon
2
3
Relationship between Haworth (flat ring) depiction and chair-form
Flat ring (Haworth projection) just gives the relative
positions of the H and OH at each carbon, one is
“above” the other. But it does not tell the positions of
the groups relative to the plane of the ring (up, down
or out)
4
Polymers are built by removing a molecule of water
between them, known as dehydration, or condensation.
Dimer formation
R-OH + HO-R
→ R-O-R + HOH
This process does not happen by itself
(It is NOT like glucose ring formation)
Rather,
like virtually all of the reactions in a cell,
it requires the aid of a
CATALYST
5
AND: Polymers are broken down by the reverse process, 6
ADDING a molecule of water between them, known as
DIMER HYDROLYSIS
R-O-R + HOH→ R-OH + HO-R
This process does not happen by itself
Rather, like virtually all of the reaction in a cell, it requires the aid
of a CATALYST
7
Building a polymer from glucose
4
CH2OH
5
2
1
3
Beta-glucose
8
4
CH2OH
4
CH2OH
5
5
2
2
1
3
Beta-glucose
1
3
Beta-glucose
Cellobiose
9
with right-hand
glucose shown
as beta
Glycosidic bond
Anomeric carbon is always one partner
C4 = equatorial out (always in glucose)
H
4
HO
CHOH
2
H
O
HO
HO
H
H
H
4
CHOH
2
H
H
H
OH
HO
HO
H
Beta-glucose residue
O
H
“Beta”-glucose residue
C1 = equatorial out (in beta glucose)
The two glucose molecules are
connected in a ~straight line in
cellobose
Beta conformation is
now locked in here
But not here
Maltose
10
with right-hand
glucose shown
as beta
Anomeric carbon is always one partner
Glycosidic bond
C4 = equatorial out (always in glucose)
H
4
HO
CHOH
2
H
O
H
H
Alpha-glucose residue
HO
HO
H
C1 = axial down (in alpha glucose)
Alpha conformation of –OH is
now locked in here
“Beta”-glucose residue
But not here
The two glucose molecules are
connected with an angle
between them in maltose
11
Equatorial bond is above the H
Equatorial bond is below the H
One is forced to draw strange “elbows”
when depicting disaccharides using the
Haworth projections. Such elbows do not exist in reality.
(here the C1 OH is “above” and the C4 OH is “below”
Whereas we just saw in actuality that they are both equatorial
in beta glucose)
12
down
H
H
Cellulose
Starch or
glycogen chain
Tinker toys
Tinker toys
Branching in starch
13
4-1
4-1
C6
4-1
4-1
4-1
6-1
4-1 4-1
4-1
4-1
4-1
Branches at carbon 6 hydroxyl
Branching  compact structure
Starch or glycogen granules,
A storage form of glucose for energy
Cytoplasm
Nucleus
14
Organelles
Starch granules
15
down
H
H
Cellulose
or glycogen chain
Cellulose
16
Cell wall of green algae
anomeric carbon
17
anomeric carbon
fructose
From handout 2-6
glucose
glucose
ribose
18
More sugars:
Mannose C6H12O6 (different arrangement of OH’s and H’s)
Galactose C6H12O6 (different arrangement of OH’s and H’s)
Deoxyribose C5H10O4 (like ribose but C2’s OH substituted by an H)
More disaccharides
Lactose = b-1-glucose to C4 of galactose (milk sugar)
Sucrose = b-2-fructose to C1- a-1-glucose (table sugar, cane sugar)
19
Metabolic intermediate
(Bacterial cell walls)
(Insect exoskeleton)
Lipids
• Soluble in organic solvents (like octane, a hydrocarbon)
• Heterogeneous class of structures
• Not very polymer-like (in terms of covalently bonded structures)
20
21
A steroid
(Abbreviation convention: Always 4 bonds to carbon. Bonds to H not shown.)
22
Fats
A fatty acid
}
Ester (functional group, acid + alcohol)
A trigyceride (fat)
23
Effect of fatty acid structure on physical properties
24
Solid fats
cis
cis
Oils
trans
trans
cis
|
No free rotation
about double bonds
H
|
C
C
|
X
H
||
X
|
H
|
C
|
H
|
C
||
Free rotation
about single bonds
- 2H
|
H
|
C
|
H
|
|
|
H
|
C
|
H
25
Adipocyte (fat storage cell)
Nucleus
Fat
globule
26
Handout 2-10
}
R=H: a phosphoester
(phosphoric acid + alcohol)
In this case: phosphatidic acid
27
[HO]
[HO]
Handout 2-10
28
HO
HO
}
R=another alcohol:
A phospho-diester
HO –CH2CH2N+H3
(alcohol = ethanolamine)
Handout 2-10
HOH
2 fatty acid
tails each
Phosphate head
Biological membranes are phospholipid bilayers
29
30
Incidentally, note the functional
groups we have met so far:
Hydroxyl
Amine
Amide
Carboxyl
Carbonyl
Aldehyde
Ketone
Ester: Carboxylic acid ester
Phosphoester
And:
Glycosidic bonds
C=C double bonds (cis and trans)
31
PROTEINS
Amino acids (the monomer of proteins)
32
At pH 7, ,most amino acids are zwitterions
(charged but electrically neutral)
33
34
+OH- ( -H+)
Net charge
+H+
50-50 charged-uncharged at ~ pH2.5 (=the pK)
50-50 charged-uncharged at ~ pH9 (=the pK)
35
Numbering (lettering) amino acids
ε-amino group
ε
δ
γ
β
Alpha-amino
Alpha-carboxyl
(attached to the α-carbon)
Alpha-carbon
Amino acid examples
36
Molecular weights 75 – 203
(MW)
Glycine (gly)
Side chain = H
Smallest (75)
One – charge
β-carboxyl:
-CH2-COOH
Tryptophan (trp)
5+6 membered
rings
Hydrophobic, largest
(203)
Lysine (lys)
One + charge
ε-amino
Alanine (ala)
One carbon
(methyl group)
-CH3
Arginine
(arg, guanido group)
One + charge
-(NH-C (NH2)NH2)+,
Aspartic acid
(asp, aspartate)
37
Shown uncharged (as on exams)
38
39
40
Amino acids in 3 dimensions
• Asymmetric carbon (4 different
groups attached)
• Stereoisomers
• Rotate polarized light
• Optical isomers
• Non-superimposable
• Mirror images
• L and D forms
From Purves text
41
Mannose
42
Condensation of amino acids to form a polypeptide
(must be catalyzed)
43
Parts of a polypeptide chain
44
The backbone is monotonous
(Without showing the R-groups)
The backbone is monotonous
It is the side chains that provide the variety
45
“Polypeptides” vs. “proteins”
•
Polypeptide = amino acids connected in a linear chain (polymer)
•
Protein = a polypeptide or several associated polypeptides (discussed later)
•
Often used synonymously
•
Peptide (as opposed to polypeptide) is smaller, even 2 AAs (dipeptide)