Question 20N.3.SL.TZ0.3d
| Date | November 2020 | Marks available | [Maximum mark: 2] | Reference code | 20N.3.SL.TZ0.3d |
| Level | SL | Paper | 3 | Time zone | TZ0 |
| Command term | Outline | Question number | d | Adapted from | N/A |
To investigate whether carbon dioxide is required for photosynthesis, a plant was irrigated using water from which carbon dioxide had been removed and was then placed in the apparatus shown in the diagram. The apparatus was left in darkness for 24 hours to destarch the leaves. Then, after several hours in light, a leaf was removed from the plant and found to contain no starch when tested. A control was performed using a second plant. A leaf from this plant tested positive for starch.
[Source: © International Baccalaureate Organization 2020.]
A chromatograph was made of the photosynthetic pigments of a leaf of the plant.
[Source: Adapted from “Diversity of Photosynthetic Pigments” by Alexander F. Motten in Tested Studies for
Laboratory Teaching, Volume 16 of the Association for Biology Laboratory Education and used by permission of the
author.]
Outline what measurements would be taken to identify pigment X.
[2]
a. the distance travelled from the origin/O to the solvent front;
b. the distance travelled by the pigment (from the origin O to X);
Accept X to solvent front if the candidate indicates that this allows O to X to be calculated.
Most candidates managed to outline what measurements would be taken to identify the pigment on the chromatogram with many identifying the pigment although this was not required.
