Question 21N.2.SL.TZ0.2
| Date | November 2021 | Marks available | [Maximum mark: 5] | Reference code | 21N.2.SL.TZ0.2 |
| Level | SL | Paper | 2 | Time zone | TZ0 |
| Command term | Label, Outline | Question number | 2 | Adapted from | N/A |
The figure shows a tripeptide.
Label one peptide bond in this molecule.
[1]
circle/bracket around peptide bond / arrow pointing to peptide bond / peptide bond labelled;
Allow either peptide bond
Allow if adjacent C=O and NH groups are included in the circle/bracket, but do not allow if other parts of the molecule are included
However, in part 2b, many did not describe the functions of the named proteins correctly. Common mistakes were assuming that all hormones are proteins, with many incorrectly giving oestrogen, testosterone and thyroxin for example. Examples were anticipated from the list of proteins found in section 2.4 of the guide.
Outline the specific functions of three named proteins.
[3]
a. Rubisco fixes CO2 from atmosphere during photosynthesis;
b. insulin controls blood glucose levels;
c. collagen forms connective tissue/ligaments;
d. spider silk forms the spider web;
e. rhodopsin involved in photoreceptor;
f. immunoglobulins/antibodies attach to antigens/pathogens;
g. actin/myosin performs muscle contraction;
h. hemoglobin carries oxygen in red blood cells;
Accept any other correct three named proteins
If an enzyme is named, the correct substrate must be stated
Outline the action taken by the diaphragm during inhalation.
[1]
contracts/flattens/becomes less domed/increases volume of thorax;