Describe the structural features of monosaccharides.

Draw the structures of \(\alpha \)-glucose and \(\beta \)-glucose.

\[\alpha {\text{ - glucose}}\quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \beta {\text{ - glucose}}\]

Two \(\alpha \)-glucose molecules condense to form the disaccharide maltose. Draw the structure of maltose.

contain carbonyl (group)/C=O;

have at least two hydroxyl/OH (groups);

Do not accept hydroxide instead of hydroxyl.

\({\text{C}}{{\text{H}}_{\text{2}}}{\text{O}}\) empirical formula;

Do not accept C_xH_2yO_y or C₆H₁₂O₆.

Award [1 max] if position of OH is correct in both structures at C1 but other groups/moieties (eg, CH₂OH) or H are missing.

Award [1 max] if the alpha and beta structures are labelled in reverse.

Only some of the candidates described a monosaccharide correctly in part (a) although its features are given in the programme guide. Drawing alpha and beta glucose was also a discriminating question.

About a third of candidates were able to score full marks on part (b)(i).

Similarly, drawing maltose in part (d)(ii) was a challenge for the majority of candidates. Many had missing hydrogen atoms or an incorrect orientation of bonds around the linkage.