| Date | May 2009 | Marks available | 3 | Reference code | 09M.3.sl.TZ2.B1 |
| Level | SL | Paper | 3 | Time zone | TZ2 |
| Command term | Explain | Question number | B1 | Adapted from | N/A |
Question
Glucose is a monomer of starch.
Explain why two cyclic isomers are formed from the straight-chain glucose and name both isomers.
[3]
b.
State the name of the two polymeric forms of starch.
[1]
c.
Markscheme
C1 is asymmetric/chiral/has four different groups;
forming two isomers where the OH-group is on a different side (of C1/ring);
\(\alpha \)-glucose and \(\beta \)-glucose;
Accept suitable diagrams as an explanation for M2.
b.
amylose and amylopectin;
c.
Examiners report
Many candidates named the two isomers correctly, few could explain clearly why they are formed. Many candidates think \(\alpha \)- and \(\beta \)-glucose are optical isomers
b.
Many candidates identified amylose and amylopectin.
c.
