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20 Cards in this Set
- Front
- Back
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Indicate whether each of the following pairs of sugars consists of anomers, epimers or an aldose or ketose.
(a)D-glyceraldehyde |
a) aldose
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Indicate whether each of the following pairs of sugars consists of anomers, epimers or an aldose or ketose.
(b) D-glucose and D-mannose |
b) 2’ epimers
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Indicate whether each of the following pairs of sugars consists of anomers, epimers or an aldose or ketose.
(c) D-glucose |
c) aldose
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Indicate whether each of the following pairs of sugars consists of anomers, epimers or an aldose or ketose.
(d) (alpha)-glucose and (Beta)-D-glucose |
d) anomers
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Indicate whether each of the following pairs of sugars consists of anomers, epimers or an aldose or ketose.
(e) dihydroxyacetone |
e) ketose
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Indicate whether each of the following pairs of sugars consists of anomers, epimers or an aldose or ketose.
(f) D-galactose & D-glucose. |
f) 4’ epimers
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Indicate whether each of the following pairs of sugars consists of anomers, epimers or an aldose or ketose.
(g) D-Fructose |
g) ketose
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What are enantiomers, aldoses and ketoses.? Give two examples (sugars) of each.
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Enantiomers or enantiomorphs are mirror image structures such as L-glucose and D-glucose; L-ribulose and D ribulose.
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What is meant by a reducing sugar?
List 3 sugars that are reducing sugars and 2 that are non-reducing sugars. |
Sugars containing a free aldehyde or keto group can reduce for eg., cupric ion, Cu+2 to cuprous ion, Cu+1.
The reducing agent is the open chain form of the aldose or ketose which is in equilibrium with the cyclic chain structure. Reducing sugars, eg., glucose, fructose, maltose, lactose; non-reducing sugars, sucrose, trehalose. Another form of a non-reducing sugar could be methyl-D-glucoside glucose. Ketoses can be methylated to form a glycoside which would also be a non-reducing sugar. |
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What does the enzyme mutarotase catalyze?
Show by an equation using the glucose isomers. |
alpha D-glucose <======> beta D-glucose
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What are enantiomers, aldoses and ketoses.? Give two examples (sugars) of each.
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Enantiomers or enantiomorphs are mirror image structures such as L-glucose and D-glucose; L-ribulose and D ribulose.
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What are aldoses?
Give two examples (sugars) of each. |
answer
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What are ketoses?
Give two examples (sugars) of each. |
answer
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D-mannose is a ??-epimer and D- galactose is a ?? epimer of D-glucose
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- 2'epimer and 4' epimer
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What are boat and chair forms?
Show the structures of the Alpha andBetaanomers of D-glucopyranose. |
The structure of the hexoses as seen either via open chain or Haworth projection erroneously suggests that the structure is planar and those projections fail to depict accurately the bond distances and bond angles of the ring atoms and substituents on each carbon. Because of the carbon tetrahedral structure, all pyran or furan rings usually take on a chair conformation (see fig. 7-8 in Lehninger).
Furan rings also have a puckered type form. The conformational structure of the alpha-anomer of D-glucopyranose is seen on page 243. The beta- anomer structure is the same except that the C 1 anomeric hydroxyl is equatorial instead of axial. |
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Give two examples of aminosugars and aldonic sugars.
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The amino sugars are D-glucosamine and D-galactosamine and N-acetyl neuraminic acid. These amino-sugars are usually N- acetylated and their structures are on p. 244 in Lehninger. Gluconic acid is seen on page 244. Other examples could be figured out. For example galactonic cid would be the 2’ epimer of gluconic acid while mannonic acid would be the 2’ epimer of gluconic acid.
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What are glycosides? Give examples .
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A glycoside is the conjugation product between the anomeric carbon of a sugar and an alcohol or an acetal oxygen of another sugar (eg., methyl glucoside).
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What is meant by equatorial and axial groups?
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Equatorial linked groups in the chair conformation are those perpendicular to the axis as seen in Fig. 7-8.
Axial groups are parallel to the axis of symmetry. The hydroxyl groups of beta-D-glucopyranose are all equatorial. Its two epimer, beta -D mannose, has its C-2-hydroxyl group as axial. |
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What are disaccharides? Give examples.
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Disaccharides are glycosides of two sugars, the same or of different sugars (eg., sucrose, maltose, lactose or cellobiose).
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What are polysaccharides? Give examples.
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Polysaccharides are molecules composed of many sugars in glycosidic linkage and the number of sugars range between 50 to >10,000.
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