Draw the Haworth projection of beta-D-sorbose Fischer projection below

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3 Draw the Haworth projection of beta-D-sorbose Fischer projection below. 1 pt CH
OH C=O H- OH HO- H H- OH CH
OH Show your work 4 Sorbose is a 3/1 pt ketose aldose puranose furanos monosaccharide disaccharide oligosaccharide polysaccharide 5 Cellulose is a homopolysaccharide of what monomer units? 7/1 pt

The Correct Answer and Explanation is:

Sure! Let’s address each of your numbered items in order:

3. Draw the Haworth projection of β-D-sorbose from its Fischer projection

Given Fischer Projection (simplified):

    CH2OH
     |
     C=O
     |
H–C–OH
     |
HO–C–H
     |
H–C–OH
     |
    CH2OH

This is D-sorbose, a ketohexose (six-carbon ketose), where the carbonyl group (C=O) is on carbon 2, making it a ketose, and it has hydroxyl groups on carbons 3, 4, and 5 in a specific orientation.

To form the Haworth projection, D-sorbose cyclizes to form a furanose ring (5-membered ring), not a pyranose (6-membered ring), since fructose (also a ketohexose) and sorbose often cyclize similarly.

Steps to Draw β-D-sorbofuranose (Haworth Projection):

  1. The ring forms between C2 (ketone) and the OH on C5.
  2. Numbering goes clockwise from the anomeric carbon (C2).
  3. In β-anomer, the anomeric OH is up (same side as CH2OH on C5 in D-isomers).
  4. Use the Fischer projection to decide whether OH groups are up or down in the ring:
  • If OH is right in Fischer → down in Haworth.
  • If OH is left in Fischer → up in Haworth.

Resulting β-D-sorbofuranose (simplified sketch):

       O
     /     \
HO–C       C–CH2OH
     \     /
      C   C
     /     \
  CH2OH   OH (β-anomer OH up)

Note: For full credit, draw the exact structure with correct stereochemistry for all carbons (C1 to C5), using proper wedge-dash notation if needed.

4. Sorbose is a:

  • ✅ Ketose (because it has a ketone group at C2)
  • ✅ Monosaccharide (single sugar unit)
  • ✅ Furanose (forms a 5-membered ring)

So, the correct options are:
ketose, monosaccharide, furanose

5. Cellulose is a homopolysaccharide of what monomer units?

Correct Answer:

β-D-glucose

Explanation

Cellulose is a homopolysaccharide, meaning it is composed of only one type of monosaccharide repeating throughout the polymer chain. In the case of cellulose, this repeating unit is β-D-glucose. These glucose units are linked together by β-1,4-glycosidic bonds. In this bond type, the hydroxyl group on the first carbon (C1) of one glucose molecule bonds to the hydroxyl on the fourth carbon (C4) of the next glucose unit, with the glucose monomers in the beta configuration.

Unlike starch (which uses α-1,4 bonds), the β-1,4 linkages in cellulose result in each glucose unit being flipped relative to the previous one. This configuration causes cellulose chains to form long, straight fibers. These fibers can align closely with one another, forming hydrogen bonds between adjacent chains. The result is a very rigid and strong structure, making cellulose an excellent structural material for plant cell walls.

Because of these β-linkages, humans (and most animals) cannot digest cellulose, as we lack the enzyme cellulase, which can hydrolyze β-1,4 bonds. In contrast, we can digest starch because we produce amylase, which breaks α-1,4 bonds.

In summary, cellulose is a homopolysaccharide consisting solely of β-D-glucose units linked via β-1,4-glycosidic bonds, resulting in a fibrous, structural polysaccharide that plays a critical role in plant cell wall integrity.

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