question on Sucrose molecule!

[xenomblack]

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hi y'all

i was doing topscore pro.. and came across one organic question that i cannot get.. hopefully somebody can answer for me before my test day...

question:
sucrose is a disaccharide composed of glucose and fructose
which of the following statements regarding sucrose is true?

a. sucrose is a non-reducing sugar
b. the anomeric carbon of glucose is linked to the fructose via an alpha - 1,2 glcysodic bond
c. the fructose unit is an example of a ketohexafuranoside.
d. both A&B are true
e. all of the above are true.

for your reference.. here's a model for sucrose..
http://en.wikipedia.org/wiki/Sucrose

and i can only see alpha 1,4, glycosidic bond..
does anybody know how it can be an alpha 1,2 bond?
and what's a ketohexafuranoside???

thanks in advance~

 

[Moni Ahmadian]

I think alpha 1,2 glycolysic bonds only occur in glycogen and not in dissach.

hi y'all

i was doing topscore pro.. and came across one organic question that i cannot get.. hopefully somebody can answer for me before my test day...

question:
sucrose is a disaccharide composed of glucose and fructose
which of the following statements regarding sucrose is true?

a. sucrose is a non-reducing sugar
b. the anomeric carbon of glucose is linked to the fructose via an alpha - 1,2 glcysodic bond
c. the fructose unit is an example of a ketohexafuranoside.
d. both A&B are true
e. all of the above are true.

for your reference.. here's a model for sucrose..
http://en.wikipedia.org/wiki/Sucrose

and i can only see alpha 1,4, glycosidic bond..
does anybody know how it can be an alpha 1,2 bond?
and what's a ketohexafuranoside???

thanks in advance~

 

[mshopeful]

A. Sucrose is a non-reducing sugar...no free anomeric carbon. Your wikipedia entry also states that.

 

[Chga]

is the answer D?

 

[xenomblack]

is the answer D?

no.. the answer is E..

 

[xenomblack]

A. Sucrose is a non-reducing sugar...no free anomeric carbon. Your wikipedia entry also states that.

yeah.. I saw that too..
possible error by Topscore anyone???

 

[mshopeful]

Actually I think Topscore is right... I think it is E. I took biochem last semester and A is true, B is true because C-1 of glucose is linked to C2 of fructose and C is true because fructose is a ketose in a 5-membered ring (furanoside). That's my guess

 

[xenomblack]

Actually I think Topscore is right... I think it is E. I took biochem last semester and A is true, B is true because C-1 of glucose is linked to C2 of fructose and C is true because fructose is a ketose in a 5-membered ring (furanoside). That's my guess

thanks for your input~