Chapter 7 + Quiz Questions Flashcards
What are 7 physiological roles of carbohydrates?
Sources of Energy, Energy Storage, Structural Roles, Cellular interaction, Cellular Identification, Information Transfer (DNA and RNA), Signaling
Carbohydrates have empirical formulas of _____ where n ≥ ?
(CH2O)n, 3 (usually 3-6)
What are the two major classes of carbohydrates, and which groups do they contain?
- Aldoses - aldehyde groups
- Ketoses - ketone groups
What is the structure of Dihydroxyacetone?
O double bonded to C, then 2 CH2OH single bonded at 45 degrees from the C
What is the structure of D-Glyceraldehyde?
Starting with a central C. Directly below single bonded is a CH2OH. To the left of central C, is a single bonded H. To the right of the central C is a single bonded OH. Above the central C is a single bonded C, going off the top C is a single bonded H 45 degrees to the right, and a double bonded O 45 degrees to the left
Most monosaccharides have ____ asymmetric carbons
multiple
The designation of a sugar as either D or L is based on ..?
The configuration of the chiral carbon most distant from the carbonyl oxygen
The designation of D or L is relative to..?
The reference molecule D-glyceraldehyde
Molecules with n chiral centers will have ___ stereoisomers
2^n. e.g. 4 chiral centers -> 16 stereoisomers
What are the 6 common sugars?
- D-Ribose, 2. D-Deoxyribose, 3. D-Glucose, 4. D-Mannose, 5. D-Galactose, 6. D-Fructose
In solution, longer carbohydrates (5 carbons and up) tend to be _____
cyclized
Cyclized carbohydrates can be found in two in two ring forms: ?
- Six-membered sugar ring - pyranose
- Five-membered sugar ring - furanose
Cyclization of glucose to glucopyranose involves the __ hydroxyl and the __ aldehyde. Cyclization renders C1 chiral, producing two stereoisomers, __ __ ___
C5, C1, α and β
What is the anomeric carbon?
The carbon that becomes chiral as a result of cyclization.
The __ and __ forms are anomers of each other
α - hydroxyl of anomeric carbon is below the plane of the sugar
β - hydroxyl of anomeric carbon is above the plane of the sugar
In solution, the α and β configurations interconvert by a process called ______
mutarotation
Mutarotation occurs through a ___ _____ and represents a change in ______
linear intermediate, configuration
In solution, glucose tends to be 2/3 __-_______, 1/3 __-______ and less than 1% _____
β-glucopyranose, α-glucopyranose, linear
Describe the cyclization of D-Fructose to Fructofuranose
Involves the C5 hydroxyl and the C2 ketone. Cyclization renders C2 chiral (anomeric carbon), producing α and β stereoisomers
True or False: fructose exists in both pyran and furan rings?
True
Linear forms of monosaccharides can be oxidized by..? The carbonyl group is oxidized to a ____ group
mild oxidizing agents like iron and copper. carboxyl
When the carbonyl group is oxidized to a carboxyl group, it allows for ______ of sugars present in blood or urine. Also defines the end of the sugar with the carbonyl carbon as being the ____ end
quantifications, reducing
What is a glycosidic bond, and what are the two types and how do they occur?
Primary structural linkage in all polymers of monosaccharides
* O-glycosidic bonds occur through oxygen
* N-glycosidic bonds occur through nitrogen
The end of the chain with a free anomeric carbon is called the ____ end of the polymer
reducing
What do the 4 components of the nomenclature of a disaccharide specify?
- The monosaccharides involved in the disaccharide.
- Their ring types (puran, furan).
- Their configurations (alpha or beta).
- Their linkages (C1-C4, etc).
Monosaccharides that have multiple hydroxyl groups means that there are many different ____ linkages are possible
glycosidic
Higher order carbohydrate structures are generated through the action of _______
glycosyltransferases
Glycosyltransferases use monosaccharides that are activated through..?
linkage with UDP
What are the 5 steps in determining disaccharide nomenclature?
1) Specify the configuration (alpha or beta) at the anomeric carbon of each monosaccharide.
2) Specify the ring form (furan or pyran) of each monosaccharide.
3) The non-reducing sugar has the suffix “osyl”.
4) The reducing sugar has the suffix “ose”.
5) Indicate in parentheses the two carbon atoms joined by the glycosidic bond with an arrow.
Lactose intolerant individuals have insufficient levels of the enzyme (lactase) that catalyzes the ______ of lactose into glucose and galactose
hydrolysis