| Date | November 2012 | Marks available | 3 | Reference code | 12N.3.SL.TZ0.9 |
| Level | Standard level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | Explain | Question number | 9 | Adapted from | N/A |
Question
Draw a labelled diagram showing the structure of a mitochondrion as seen under an electron microscope.
Explain the relationship between the structure of the mitochondrion and its function.
Markscheme
Award [1] for two correct labels.
outer membrane;
inner membrane – showing folding to cristae;
cristae – shown as shelf-like infoldings of inner membrane;
matrix;
intermembrane space;
(70S) ribosomes – shown as small dots, not too large;
(naked) loop of DNA;
Award [2 max] for a poorly drawn or inaccurate diagram.
matrix is site of reactions of Krebs cycle;
thin intermembrane space to build up high proton concentration/[H+];
ATPase enzymes on inner membrane to produce ATP as protons pass back to matrix;
folded inner membrane / cristae to increase surface area (for electron transport chain);
ribosomes to make enzymes (required for Krebs cycle);
Examiners report
Drawings of the mitochondrion were often awarded full marks in (a).
Many candidates, however, found it more difficult to explain the relationship between structure and function of the mitochondrion in (b) but good candidates knew this.
