Sugar structure

Question 1

Whats the difference between an aldose and ketose sugar and which one is glucose

Answer 1

Aldose has aldehyde group on C1 and Ketose has ketone group. Glucose is aldose

Question 2

What is the difference between D and L isomers of Glucose

Answer 2

D & L isomers are straight chains with the OH group attached to the furthest chiral carbon from the aldehyde group (C5) determines D and L.

L is OH group on the Left
D is OH group on the Right

Question 3

What is the straight chain isomer of glucose found in nature

Answer 3

D - glucose

Question 4

When fisher projection folds to reversible cyclic form Harworth projection, which parts are above the plane of the ring and which are below

Answer 4

Groups on the Left of the chain are Above the ring plane, whereas Groups on the Right of the chain are Below the ring plane. The last group (6) is above the ring plane

Question 5

What is the difference between alpha and beta anomers of a straight chain

Answer 5

Anomers differ by orientation of OH on C1 (after O) and this is because aldehyde group can be attacked from below or above.

A is OH on below
B is OH on above

Question 6

Does the D,L isomer of glucose affect the anomers

Answer 6

No because both D and L glucoses have 2 anomers each- the OH on C5 becomes the C-O-

Question 7

Compare the similarities and difference of structure of Glycogen+ Starch with Cellulose and therefore their relative solubility (break down easyness)

Answer 7

Glycogen, Starch and Cellulose are all polysaccarides of glucose. However St+Gly use A- glucose while Cellu uses B-glucose. The different 1-4 glycosidic linkage means that the quaternary structure is different.
a-glucose makes a helical structure, with glycogen having branches due to some 1,6 branches too. While Cellulose makes a straight beta sheet with no branches (no 1,6).

As a result the enzyme in humans can only do a-1,4 linkages so can’t break down the B-1,4 in cellulose.