| Date | November 2011 | Marks available | 3 | Reference code | 11N.3.sl.TZ0.B4 |
| Level | SL | Paper | 3 | Time zone | TZ0 |
| Command term | Compare | Question number | B4 | Adapted from | N/A |
Question
Starch and cellulose are polysaccharides found in many plants.
Compare the structures of starch and cellulose.
Markscheme
both are polymers of glucose / both contain glycosidic linkages;
starch is formed from \(\alpha \)-glucose / can have \(\alpha \)-1,6 linkages (and \(\alpha \)-1,4 linkages) / amylopectin form is branched;
cellulose is formed from \(\beta \)-glucose/has \(\beta \)-1,4 linkages / does not have 1,6 linkages / is not branched / is only straight-chain;
Examiners report
Many candidates had some idea of the α-glucose and β-glucose origins of starch and cellulose respectively, but it was disappointing to see weak answers where candidates compared other features/properties, such as digestibility or solubility, instead of comparing the structures as it was asked for.
