| Date | May 2015 | Marks available | 2 | Reference code | 15M.2.SL.TZ2.2 |
| Level | Standard level | Paper | Paper 2 | Time zone | Time zone 2 |
| Command term | Annotate | Question number | 2 | Adapted from | N/A |
Question
Outline the cell theory
Annotate the electron micrograph of the Escherichia coli cell with the function of the structures labelled I and II.
Calculate the magnification of the electron micrograph.
Markscheme
a. living things are composed of cells;
b. cells are the basic/smallest unit of life;
c. cells come from pre-existing cells;
Do not accept cells are the “smallest organisms”.
Do not accept “cells are the building blocks” of life on its own.
a. I: locomotion;
b. II: attachment to surfaces / holds bacteria together / conjugation;
Do not accept “exchange material” on its own.
If more than one function is given, mark the first answer only.
×15 000 (accept answers in the range of × 14 000 to × 16 000)
Examiners report
Most gained both marks for their knowledge of cell theory in part a.
Students who read the rubric correctly in b scored well. However approximately half of the students read "label" instead of "function".
A disappointing number had no idea how to calculate the magnification (15000X) and some answers showed no concept of scale, with answers such as 0.15 X or 5x10-7 X.
