| Date | May 2009 | Marks available | 2 | Reference code | 09M.2.HL.TZ1.3 |
| Level | Higher level | Paper | Paper 2 | Time zone | Time zone 1 |
| Command term | Explain | Question number | 3 | Adapted from | N/A |
Question
The electron micrograph below shows a section of a liver cell.
Identify the structure labelled I and state one function of this structure.
Calculate the magnification of this photograph. Show your working.
Explain the evidence from the electron micrograph that indicates that liver cells are very active.
Markscheme
nucleus contains genetic information / is site of DNA replication / site of RNA transcription;
nuclear membrane/envelope (which has pores) allowing exchange of substances between nucleus and cytoplasm;
magnification =
(Accept answers in range 6000–6200 . Do not deduct for differences in precision in calculation.)
large number of mitochondria;
to meet energy demand/ATP production (needed for high metabolic activity);
or
large amount of rER;
indicates high rate of protein synthesis;
Examiners report
Most candidates identified the nucleus/nuclear membrane but did not accurately state its function.
Relative to magnification questions on previous exams, this question was poorly answered. Correct measurement was common, though precision of measurements was a problem for some. Changing between units proved to be more difficult. Some candidates used the scale bar to determine the width of the micrograph without realizing that the magnification could be calculated from the scale bar itself.
This question was correctly answered by most candidates with candidates both recognizing structures and correctly relating structures to evidence of activity.
