Urease is an enzyme that breaks down urea.
A student measures the rate of this reaction at different concentrations of urea. She uses the same volume and concentration of urease each time, at 25 ∘C25\ ^\circ\text{C}25 ∘C.
The Table shows her results.
Table
| Concentration of urea in g/dm3\text{g/dm}^3g/dm3 | Rate of reaction in arbitrary units |
|---|---|
| 0 | 0 |
| 5 | 14 |
| 10 | 25 |
| 15 | 33 |
| 20 | 38 |
| 25 | 40 |
| 30 | 40 |
| 35 | 40 |
Explain why the rate of reaction does not increase above a urea concentration of 25 g/dm3.
The student repeats the investigation using twice the concentration of urease.
Predict and explain the effect on the maximum rate of reaction.
Urease breaks down urea but does not break down glucose.
Explain why.
Enzymes such as urease have an important role in metabolism.
Explain why a cell needs to make many different enzymes.
184 exam-style questions on OCR GCSE Biology 1.2 What happens in cells (and what do cells need)?, covering 1.2.1 Structure of DNA, 1.2.2 Nucleotides and complementary bases, 1.2.3 Protein synthesis, 1.2.4 DNA structure and the proteins made, 1.2.5 Investigating enzymatic reactions, and 1.2.6 Mechanism of enzyme action. Each one has a worked solution and a mark scheme showing where the marks go.