Please answer ASAP. When two carbohydrates are epimers; A) one is a pyranose, th

Question

Please answer ASAP.
When two carbohydrates are epimers; A) one is a pyranose, the other a furanose. B) one is an aldose, the other a ketose. C) they differ in length by one carbon. D) they differ only in the stereo chemistry around one carbon atom. E) they rotate plane-polarized light in the same direction. When the linear form of aldose sugar cyclizes. the product is a(n): A) anhydride. B) glycoside. C) hemiacetal. D) hemiketal. E) oligosaccharide. Which of following is an anomeric pair? A) D-glucose and D-fructose B) D-glucose and L-fructose C) D-glucose and L-glucose D) alpha -D-glucose and beta D-glucose E) alpha - D - glucose and beta - L - glucose Consider following disaccharide, maltose, and answer questions (9-11) (9) The abbreviated name of above disaccharide, maltose is: A) alpha-D-glucopyranosyl -(1-4)-D-glucopyranose. B) alpha-D-glucopyranosyl -(4-l)-L-glucopyranose. C) alpha-D-glucofuranosyl -(4-l)-D- glucofuranose. D) alpha-D-glucofuranosyl -(1-4)-L- glucofuranosyl. E) None of the above is true. Number of anomeric carbons in above disaccharide, maltose are? A) 4. B) 2. C) 3. D) I. E) 0.

Explanation / Answer

Q6

D) is true, since both must be stereoisomers, and the only thing that changes is the assymetrical carbon (stereocarbon) configuration

Q7

when aldose sugar cyclizes it becomes an hemiacetal...

anhydride cna't be, this is related to no water molecule

oligosacharide can't be, since this means at leats 3 or more molecules

Q8

anomeric pair --> they must be the same configuration, that is, "D" configuration but must have alpha and beta array (this is what differs them!)

so..

a b can't be since they are not the same specie, i.e. glucose/glucose

c is not stated, w emust have beta + alph details

choose D

since E has D and L configurations, which is not the definition of tha nomer

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