Question 23M.1A.HL.TZ1.28
| Date | May 2023 | Marks available | [Maximum mark: 1] | Reference code | 23M.1A.HL.TZ1.28 |
| Level | HL | Paper | 1A | Time zone | TZ1 |
| Command term | Question number | 28 | Adapted from | N/A |
Through a series of enzymatic reactions, the amino acid threonine is converted to isoleucine. The graph shows the rate of reaction of threonine deaminase according to the concentration of its substrate threonine, with and without the presence of isoleucine.
[Source: Calhoun, D.H., Rimernian, R.A. and Hatfield, G.W., 1973.
Threonine Deaminase from Escherichia coli.
I. Purification and Properties. The Journal Of Biological Chemistry,
248(10), pp. 3511–3516. Open Access.]
What can be seen from these results?
A. Threonine deaminase only works in the presence of isoleucine.
B. Isoleucine inhibits threonine deaminase at low concentrations of threonine.
C. Production of isoleucine is inhibited at high concentration of threonine.
D. End-product inhibition controls the production of threonine deaminase.
[1]
B