Chapter 11 Notes Flashcards
CHOs with ketones?
ketoses
CHOs with aldehydes?
aldoses
What are the most common 6-carbon CHOs?
allose, altrose, glucose, mannose, gulose, idose, galactose, talose
Which 6-carbon CHOs are considered epimers of each other?
glucose, mannose, galactose
Mannose and galactose are __.
disterioisomer
When dissolved in water, hexoses assume ring structures and form structures referred to as __ and ___.
hemiacetals, hemiketals
Mutarotation?
when the anomeric carbon atom can exist in equilibrium between 2 stereochemial states: alpha or beta (anomers)
What are the most reactive compound groups of CHOs?
anomeric carbon and hydroxyl group
what is unique about fructose?
can form both 5- and 6- membered rings where each forms a new chiral center
Why is the chair structure more favored?
due to less steric hindrance - beta form preferred at 66%
Monosaccharides may react with alchols and amines to form modified monosaccharides via __ bonding.
glycosidic
Difference between O and N glycosidic bonds?
O-oxygen attached
N-Nitrogen attached
Why are aldoses referred to as reducing sugars?
they can undergo oxidation-reduction reactions that reduce metals such as Ca or Ag
Fehling’s reagent?
Cu2+ (oxidized form)
In the presence of reducing sugars, Fehlings reagent becomes reduced to __.
Cu+ which reacts with oxygen and forms a red precipitate
Where does modification occur?
only at the anomeric hydroxyl group because it is the only one that can open up
How can CHO be modified?
by addition of various substituents to yield biologically important molecules
Where does reduction occur?
at functional group
__ bonds often form between monosaccharides to produce disaccharides and larger polysaccharides.
glycosidic bonds
Once a __ bond is formed, the reducing properties of the sugar are lost.
glycosidic
polysaccharides?
large polymeric oligosaccharides formed by linkage of multiple monosaccharides called polysaccharides; play an important role in energy storage: starch (amylopectin and amylose) and glycogen
What makes cellulose, starch, and glycogen so strong?
the many nonreducing ends in glycogen allow for rapid metabolism and release and add glucose molecules (enzymes attack nonreducing ends to mobilize glycogen more easily - due to branching); unbranched beta1,4 linkages between glucose allows maximum hydrogen bonding and stacking of linear chains - the resulting structure is fibril-like with high tensile strength due to thier repeating hydrogen bonding patterns
CHOs can be attached to proteins to form __.
glycoproteins
When N-glycosidic bond = forms __.
asparagine
when O-glycosidic bond = forms __.
serine
Which AA combination allows for the sugar to form for N-glycosidic bond?
Asn-X-Ser or Asn-X-Thr
What is the specific AA sequence for sugar to form for O-glycosidic bond?
no particular sequence - just attaches freely
