Carbohydrate Structure Flashcards
What are the 3 types of isomers?
Constitutional
Configurational
Conformational
Describe constitutional isomers
The order of the atoms changes
All constitutional isomers are Tautomers- fluctuate between the alcohol and the carbonyl group
If the alcohol points to the right on the fisher projection it is D
If it points to the left, it is L
_____ _______are the linear versions of the carbohydrates
Fisher Projections
*Note that the carbon numbering starts at the carbonyl/alcohol end of the aldose
Describe Stereoisomers
They have the same connectivity, but different spatial organizations
Describe configurational isomers
They have chiral carbons- 4 different groups attached to a single carbon
What are enantiomers?
Mirror images at all chiral centers
What are diastereomers?
Not mirror images at every chiral center, but note that they do have multiple chiral centers
______ _______ are the cyclical versions of carbohydrates
Hawthorn Projections
For the ring form (Hawthorn projection), where is the anomeric carbon?
Whichever carbon is attached to 2 oxygens
For the Fisher projection (linear form), how can you tell which is the anomeric carbon?
It will be the carbon that starts its life as a carbonyl because it loses the double bond and gains an oxygen when converted to the ring form
When the carbonyl in the fisher projection is converted into an alcohol in the Hawthorn projection, if the alcohol on the anomeric carbon is pointing up what does this mean and if it is pointing down what does this mean?
Up- Beta
Down- Alpha
What is an anomer?
They differ at the anomeric carbon only, example: alpha verses beta orientation
*Note that an anomer is a type of diastereomer
What is an epimer?
Differ at any other carbon than the anomeric carbon
- Note that this means they must have the same alpha or beta orientation
- Note that an epimer is a type of diastereomer
If during the fisher projections the alcohols are on the LEFT side, what does this mean for the Hawthorn projections?
They will be pointing up
If during the fisher projections the alcohols are on the RIGHT side, what does this mean for the Hawthorn projections?
They will be pointing down
What are the 2 conformations for a 4 membered ring and what is that ring called?
Furanose- 4 membered ring
C-3’- endo
C-2’-endo
What are the 2 conformations for a 6 membered ring and what is that ring called?
Pyranose- 6 membered ring
Boat
Chair
What are the 4 aldoses we need to know, and how many carbons are in each?
Glyceraldehyde- Triose (3)
Ribose- Pentose (5)
Glucose- Hexose (6)
Galactose- Hexose (6)
What are the 3 ketoses we need to know, and how many carbons are in each?
Dihydroxyacetone- Triose
Ribulose- Pentose
Fructose- Hexose
Take a look at slide 23, lecture 19 and know the structures of the sugars and how to convert them to eachother
Do this
How do we form Fucose (yes this is the right spelling)
It is a Galactose derivative, at position carbon 6 the alcohol has been exchanged for a methyl
What s the only L-monosaccharide made and used by mammals?
Fucose
How is Fucose important?
Part of the A/B/O blood antigens
Excess free fucose in the blood shows signs of: Liver damage Cancer Diabetes Heart Disease
How is phosphorylation important for modifying monosaccharides?
Part of nucleic acid structure
Adds a negative charge
Where do we get the phosphate from during phosphorylation of monosaccharides?
ATP
How do we know where the phosphate goes during phosphorylation of monosaccharides?
The name tells you where to put it…
Glucose-6- phosphate… you replace the hydrogen on carbon 6 with a phosphate
When oxidizing monosaccharides, where does the acid attack the ring?
And what 2 strucutres can oxidizing a monosaccharide make? (how many rounds of oxidation to get to each structure)
The acid (in our case hydroxyl) attacks the anomeric carbon and expose it
By doing this, we make acids and lactones
- Acids are made after one round of oxidation
- Lactones are made after 2 rounds of oxidation
What does reducing a monosaccharide at the carbonyl make?
Give an example
Alditols
Example: Sorbitol can cause cataracts if it accumulates in the lens of the eye
Describe amino sugars modification of monosaccharides. Where are they found, how are they made?
Found in branched polysaccharides (Ex. cell walls)
Formed by N-linked glycosides:
- Amine group
- Acetyl group
- Lactic Acid
*Note that the amine group always has to be directly attached to the ring. If the sugar does not have an amine group already present, whatever modification is being added must start with an amine.
What is the difference between glucose and galactose in the ring conformation?
Glucose has its hydroxyl at carbon 4 pointing down
Galactose has its hydroxyl at carbon 4 pointing up
During the methylation modification to a monosaccharide, where will the methyl group be added?
To put a methyl group on a monosaccharide, it must be connected to an alcohol because the oxygen will attack the anomeric carbon to add the methyl group
Describe the O-linked glycosides modification of monosaccharides. What 2 toxins utilize this method and what are the effects of each?
Oubain- monosaccharide attached to a steroid. Locks the Na/K pump in the E2 conformation so there is an accumulation of Na because it cannot be released.
Amygdalin- disaccharide attached to a weird group with a cyanide on it. This releases cyanide, which is really bad.
What are the essential Monosaccharides?
What are their structures
D-Glucose
D-Galactose
D-Mannose
D-Xylose (don’t need to know the structures)
What are the 3 essential amino sugars?
GlcNAc- Glucose with amino acetyl group attached
GalNAc- Galactose with amino acetyl group attached
Sialic Acid
What are the monosaccharides that make up the disaccharide, Maltose? What is the name of the connection for Maltose?
Slide 33- lectue 19
Glucose + Glucose
alpha- D- Glucopyranosyl (1–> 4) alpha- D Glucopyranose
What are the monosaccharides that make up the disaccharide, Sucrose? What is the name of the connection for Sucrose?
Slide 33- lectue 19
Glucose + Fructose
alpha- D- Glucopyranosyl (1 –> 2) Beta- D-Fructofuranoside
What are the monosaccharides that make up the disaccharide, Lactose? What is the name of the connection for Lactose?
Slide 33- lectue 19
Glucose + Galactose
Beta-D- Galactopyranosyl (1–>4) Beta-D- Glucopyranose
What is the role of Sucrose?
A final product of photosynthesis, used as a primary source of energy in organisms that photosynthesize
What is the role of Lactose?
Major animal energy source
What is the role of Maltose?
A major circulatory sugar in insects, used for energy
What are the 3 roles of Polysaccharides?
- Glucose Storage
- Structure
- Protein Diversity
Describe the 1st role of polysaccharides, Glucose Storage. Give 2 examples
Less compact than lipid storage because it likes to interact with water therefore making it more volumenous
Amylopectin- branched
Amylose- unbranched
Describe the 2nd role of polysaccharides, Structure.
Cellulose- Beta sheets. (1–> 4) Beta linkage
Chitin- is universal in providing structure. (1–>4) Beta linkage
Describe the 3rd role of polysaccharides, Protein Diversity. What are the overall 2 types?
N-linked (Only amino acid that attaches the protein to the monosaccharide is Asparagine, Asn)
O-linked (Only amino acids that attach the protein to the monosaccharide are Serine or Threonine)
Describe the 3rd role of polysaccharides, Protein Diversity. What are the 3 types?
Glycoproteins
Glycosaminoglycans
Mucins
What is the role of Glycoproteins in terms of adding protein diversity and what is the stipulation to be added?
Protein > Sugar (by weight) - Stipulation
On membrane proteins –> cell adhesion
On soluble proteins –> cell signaling
Example: Erythropoietin is a glycoprotein hormone that stimulates RBC production
What is the role of Glycosaminoglycans in terms of adding protein diversity and what is the stipulation to be added? What is it made up of?
Sugar > Protein (by weight)- Stipulation
Repeating disaccharide units
These are the sugar components for proteoglycans and they are important for:
- Carilage
- Blood clotting
- Chitin
What is the role of Mucins in terms of adding protein diversity and what is the stipulation to be added?
Sugar > Protein (by weight)
Lubrication= protection + hydration
What are glycolipids used for and where are they found? How do you convert between A, B, and O in terms of glycolipids?
Found on the surface of cell memebranes and are used to recognize self from nonself.
O –> B by adding Galactose
O –> A by adding GalNAc
