Question 22M.2.SL.TZ1.2
| Date | May 2022 | Marks available | [Maximum mark: 4] | Reference code | 22M.2.SL.TZ1.2 |
| Level | SL | Paper | 2 | Time zone | TZ1 |
| Command term | Explain, Outline, State | Question number | 2 | Adapted from | N/A |
The diagrams represent the structure of a protein before and after it has become denatured.
[Source: Dean Williams, L., 2019. Molecular Interactions. [online] Available at: https://ww2.chemistry.gatech.edu/~lw26/
structure/molecular_interactions/mol_int.html [Accessed 20 August 2019].]
State how many different types of amino acid there are, which can become part of a polypeptide when mRNA is translated.
[1]
20;
Amazingly, most candidates missed gaining the mark for this question: a huge variety of incorrect numbers appeared, "4" was most frequent. Many candidates seemed to confuse the 4 nucleotide bases with the 20 amino acids.
Outline one cause of denaturation in proteins.
[1]
- increase in temperature/heat;
- change of pH;
- salt;
- heavy metals;
Most candidates answered these questions about enzymes either really well or very poorly. Some erroneous answers mistook the active site as being separate to the enzyme or part of the substrate. Another problem had to do with temperature as a denaturant. Lowering the temperature does not denature the enzyme, though it may slow the reaction down. The candidate needed to say increased or hot temperature to gain a mark.
Explain how denaturation affects the activity of an enzyme.
[2]
- changes the shape of the (active site) of the enzyme;
- substrate would be unable to attach to the enzyme/active site;
- slows the enzyme activity / prevents reaction/catalysis from proceeding;
