Chapter 7 Carbohydrates

Question 1

1 Why are monosaccharides appropriately named carbohydrates?

Answer 1

Cn(H2O)n

Question 2

2) Why are monosaccharides soluble in water but not in non-polar solvents?

Answer 2

Soluble in water, because of the presence of multiple hydroxyl groups.

Question 3

3) What are the naming conventions for monosaccharides?

Answer 3

aldoses vs. ketoses. and length

Question 4

4) The word “Chiral” is derived from the greek word meaning “hand.” How does this relate to the structure of carbohydrates?

Answer 4

Carbohydrates, excluding dihydroxyaetone, are chiral. each molecule has 2^n stereoisomers. Where n = the number of carbons - 2

Question 5

5) How many D-isomers would an aldopentose have? How many total isomers?

Answer 5

2^3

Question 6

6) Is galactose and epimer of mannose

Answer 6

No

Question 7

7) In an aqueous solution of D-glucose, why will there always be a very small amount of the linear form of the monosaccharide?

Answer 7

The ring form is more stable and is formed readily

Question 8

Cyclization and stereo-isomerism

Answer 8

when a saccharide cyclizes, there is a new chiral center that is generated

Question 9

Anomers

Answer 9

isomeric forms of a monosaccharide that differ only in their configuration about the hemiacetal or hemiketal carbon

Question 10

pyranoses

Answer 10

6 membered rings

Question 11

furanose

Answer 11

hemiketal 5 membered ring

Question 12

10) Why is phosphorylation of sugars beneficial to a cell?

Answer 12

1) Traps sugars inside of the cell 2) activates sugars for chemical processing 3) Sugar phosphates are relatively stable

Question 13

A sugar can only be oxidized in its…

Answer 13

linear form. In a polysaccharide, the anomeric carbons not involved in the glycosidic bond are non reducing.

Question 14

Q # 15 What are the structural and functional differences between homopolysaccharides and heteropolysaccharides?

Answer 14

Homo- one anomeric species; hetero - more than one anomeric species

Question 15

Starch

Answer 15

contains long unbranched chains of D-glucose connected by (alpha 1->4) linkages;

Question 16

Amylopectin

Answer 16

contains long branched chains of D-glucose; connected by (alpha 1->4) linkages; branch points are every 24 to 30 residues with (alpha 1->6) linkages

Question 17

Glycogen

Answer 17

main storage polysaccharide in animals; ( alpha 1->4) linkages with (alpha 1->6) branched linkages on every 8-12 residues; each glycogen molecule has n+1 reducing ends;