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Date May 2011 Marks available 2 Reference code 11M.3.hl.TZ1.B5
Level HL Paper 3 Time zone TZ1
Command term Identify Question number B5 Adapted from N/A

Question

In aerobic respiration, the metabolism of glucose takes place using the processes of oxidation and reduction.

Identify the molecule that undergoes oxidation and state the half-equation for the process.

[2]
a.

Identify the molecule that undergoes reduction and state the half-equation for the process.

[2]
b.

Markscheme

glucose/\({{\text{C}}_{\text{6}}}{{\text{H}}_{{\text{12}}}}{{\text{O}}_{\text{6}}}\);

\({{\text{C}}_6}{{\text{H}}_{12}}{{\text{O}}_6} + {\text{6}}{{\text{H}}_2}{\text{O}} \to {\text{6C}}{{\text{O}}_2} + {\text{24}}{{\text{H}}^ + } + {\text{24}}{{\text{e}}^ - }\);

a.

oxygen/\({{\text{O}}_{\text{2}}}\);

\({\text{6}}{{\text{O}}_2} + {\text{24}}{{\text{H}}^ + } + {\text{24}}{{\text{e}}^ - } \to {\text{12}}{{\text{H}}_2}{\text{O}}\);

Accept equation divided by 6.

Award [2 max] if (a) and (b) are reversed and all 4 marking points are correct.

b.

Examiners report

Majority of candidates identified that glucose was oxidised and oxygen was reduced.

a.

It was very rare to see correct half-equations.

b.

Syllabus sections

Options » B: Biochemistry » B.1 Introduction to biochemistry

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