Lecture 19 Flashcards
State and describe the 3 types of isomers
Constitutional: the order of atoms changes
Configurational: have chiral bonds (this is how they form diastereomers and enantiomers)
Conformational: have reversible rotation changes
What type of isomer are tautomers?
tautomers are constitutional isomers
What are fisher projections? where does the carbon numbering on these projections begin?
linear drawings of carbohydrates
Carbon numbering starts at the carbonyl (Double bond to O) end of the aldose
Stereoisomers have the same _____ but different _____ ______. State the 2 “types of isomers” that are considered to be stereoisomers.
connectivity
spatial organizations
Both Configurational and Conformational isomers are stereoisomers
(constitutional isomers are the only type of isomer that is not considered to be a stereoisomer)
What type of carbon do configurational isomers feature?
chiral carbons
Compare enantiomers (what do these create) and diastereomers (include similarities)
Enantiomers: the mirror images that occur at ALL chiral centers in a structure
These occur at all chiral carbons and Form D and L forms of the same molecule
Diastereomers: are NOT mirror images overall
These require multiple chiral centers)
Both are configurational isomers
Define Haworth Projections
Haworth Projections: the cyclical versions of carbohydrates (another method of drawing their structures)
Compare anomers and Epimers (differences and similarities)
Anomers: differ at the anomeric carbon ONLY (alpha vs beta)
Epimer: differs ANYWHERE besides the anomeric carbon (same alpha or beta but different somewhere else)
Both are diastereomers
Write out the 7 steps in this lecture
7 steps
True or False:
Conformational Isomers have irreversible rotation changes. explain.
FALSE
Conformational isomers have REVERSIBLE rotation changes
In conformational isomers, what determines if the structure will be “boat or chair” form? what term describes this influence?
The larger functional groups on the molecule
This is an example of steric hindrance
What is formed when one or more hydroxyl is replaced on a monosaccharide?
glycosides
Describe how following modified chemical modifications are achieved if you start with an unmodified monosaccharide:
Fucose:
Esters:
Oxidation and REduction:
N-linkages:
O-linkages:
Fucose: weird one
Esters: phosphorylation
Oxidation and REduction: Alcohols
N-linkages: AA’s and nucleotides
O-linkages: Methylation/Toxins
State the 2 tautomers that we need to know from this lecture
Ribose (aldose)
Ribulose (ketose)
These are the same number of atoms but Ribose has a =O group at C1, while Ribulose has a =O group at C2
Define Anomeric carbon
Anomeric Carbon: the Carbon atom that is 1 position clockwise from the Carbonyl
When converting from fisher to haworth structures, what determines whether the structure is considered to be in the alpha or beta configuration?
Alpha configurations have the OH that used to be the C=O, pointing DOWN
Beta configurations have the OH that used to be the C=O, pointing UP
State the galactose derivative that is the only L-monosaccharide that is made and used by mammals
Fucose (“its the weird one”)
What monosaccharide modification adds a negative charge and forms important reactive intermediates in carbohydrate metabolism
Phosphorylation
True or False:
ATP is a phosphorylated sugar. explain.
True
ATP is ADP (sugar) with another phosphate on it
The monosaccharide modifications of oxidation and reduction are very similar in that they both occur at the carbonyl. Which of these creates acids, lactones, and alditols? Which of these can create sorbitol and cause cataracts and which is used in diabetes urine tests?
Oxidation of reducing sugars at the carbonyl makes acids and lactones
Oxidation is used in diabetes urine tests
Reduction at the carbonyl makes alditols
Reduction can create sorbitol and cause cataracts
What type of modified monosaccharide is found in branched polysaccharides? how is this modified monosaccharide formed?
Amino sugars
Amino sugars are formed via N-linkages
Describe the type of linkage that Methylation is formed with. How does this compare to amino sugars?
Methylation is achieved through O-linkages
This uses the same reaction that is used to create polysaccharides in the formation of Amino sugars, HOWEVER, Methylation does not use a sugar
State the 8 essential Monosaccharides (4 regular, 1 oddball, 3 Amino sugars)
"regular": D-Glucose D-Galatose D-Mannose D-Xylose
“oddball”:
L-Fucose
Amino Sugars:
GlcNAc
GalNac
Sialic Acid
For the following disaccharide, state the 2 monosaccharides that are linked in order to form it:
(indicate which positions link together)
Maltose
Maltose = Alpha-D-Glucose (C1 position) + Alpha-D-Glucose (C4 position)
For the following disaccharide, state the 2 monosaccharides that are linked in order to form it:
(indicate which positions link together)
Lactose
Lactose = Beta-D-Galactose (C1 position) + Beta-D-Glucose (C4 position)
For the following disaccharide, state the 2 monosaccharides that are linked in order to form it:
(indicate which positions link together)
Sucrose
Sucrose = Alpha-D-Glucose (C1 position) + Beta-D-Fructose (C2 position)
State the 3 roles of polysaccharides
- Glucose Storage
- Structure
- Protein Diversity
Compare Amylopectin/Glycogen with Amylose in terms of their structure. Also include what role of polysaccharides they are most involved in
Amylopectin/Glycogen are branched
Amylose is unbranched
Both of these are involved in the glucose storage role of polysaccharides
Name the 2 polysaccharides that are involved in the “structure” role of polysaccharides. Which of these has alpha and beta bonds and which of these is considered the “universal structural polysaccharide?
Cellulose: Has alpha bonds (forms a helical structure) and beta bonds (forms a beta sheet looking structure
(these bonds all occur at once to give it it’s rigidity)
Chitin: is considered the universal structural polysaccharide
N-links and O-links contribute to the role of protein diversity that polysaccharides are involved in. What AA’s do these 2 linkages lead to?
N-Linked = Asn only
O-linked = Ser or Thr
Compare Glycoproteins, Glycosaminoglycans, and Mucins in terms of their “protein to sugar composition” and locations in the body they are found.
Glycoproteins: Protein > Sugar (by weight)
Found on membrane proteins (in cell adhesion) and on soluble proteins (in cell signaling)
Glycosaminoglycans: Protein < Sugar (by weight)
In repeating disaccharide units to form the sugar component of proteoglycans
Mucins: Protein < Sugar (by weight)
In mucus to provide lubrication (protection + hydration)
What type of polysaccharide decorates cell membranes and are used to recognize self/non-self cells? Give an example of this in action.
Glycolipids
A, B, and O antigens are just sugars added to blood cell surfaces
How are altidols formed from monosaccharides? What about the process that makes acids and lactones?
reduction at the carbonyl makes altidols
Oxidation at the carbonyl makes acids and lactones
