| Date | May 2011 | Marks available | 3 | Reference code | 11M.3.SL.TZ1.9 |
| Level | Standard level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | Draw | Question number | 9 | Adapted from | N/A |
Question
Draw a labelled diagram of a mitochondrion.
Explain how the structure of a mitochondrion is adapted for its function.
Markscheme
Award [1] for each structure clearly drawn and clearly labelled.
overall circular or cylindrical shape;
smooth outer membrane and inner folded membrane shown close together;
cristae, shown as thin folds of the inner membrane orientated towards the inside of the mitochondrion;
matrix;
ribosomes/circular DNA;
intermembrane space;
large inner surface area of cristae for respiratory complexes/electron transport chains;
matrix contains/encloses DNA and ribosomes for protein (enzyme) synthesis / Krebs cycle enzymes;
(double) membrane(s) isolates metabolic processes from the rest of the cytoplasm;
small IM space between inner and outer membranes for accumulation of protons;
Answers must clearly link a structure to a function for a mark.
Examiners report
The standard of drawing was fairly good, but common errors included cristae which were too wide, inner and outer membranes too far apart, and often three outer membranes instead of two. Labelling was fairly good on the whole.
As the question asked candidates to explain the relationship of structure to function, students were expected to link a specific function to a particular mitochondrial structure, which many failed to do.
