Date | May 2021 | Marks available | 1 | Reference code | 21M.1.SL.TZ2.11 |
Level | Standard level | Paper | Paper 1 | Time zone | Time zone 2 |
Command term | Question number | 11 | Adapted from | N/A |
Question
The graph shows the results of an experimental investigation that compared the rates at which lactose, glucose and galactose are broken down in the process of anaerobic cellular respiration by the yeast Torulopsis cremoris.
[Source: Rogosa, M., 1948 Mechanism of the Fermentation of Lactose by Yeasts. Journal of Biological Chemistry, 175, p.418. (CC BY 4.0) https://creativecommons.org/licenses/by/4.0/.]
What can be concluded from these results?
A. Cellular respiration of lactose involves the production of glucose and galactose.
B. The breakdown of glucose and galactose occurs more slowly in the presence of lactose.
C. The rate of cellular respiration is greater for glucose than for lactose and galactose.
D. The percentage of sugar remaining after 42 hours is greater for galactose than glucose.
Markscheme
D
Examiners report
Some teachers commented that this question would be difficult for the students as they were unable to carry out experiments in class. However, the statistics show that the question performed well in terms of difficulty and discrimination. The theory of anaerobic respiration is required in 2.8 (Cell respiration). This question can be answered simply by looking at the graphs.