An enzyme-controlled reaction is investigated at different temperatures. The enzyme concentration, substrate concentration and pH are kept constant. The mixture is held at 55 ∘C55\ ^\circ\text{C}55 ∘C for five minutes before it is cooled to 35 ∘C35\ ^\circ\text{C}35 ∘C.
| Temperature or treatment | Mean rate / s−1\text{s}^{-1}s−1 |
|---|---|
| 35 ∘C35\ ^\circ\text{C}35 ∘C | 0.80 |
| 45 ∘C45\ ^\circ\text{C}45 ∘C | 1.20 |
| 55 ∘C55\ ^\circ\text{C}55 ∘C | 0.31 |
| Cooled to 35 ∘C35\ ^\circ\text{C}35 ∘C after treatment at 55 ∘C55\ ^\circ\text{C}55 ∘C | 0.30 |
Use the data to explain the decrease in rate at 55 ∘C55\ ^\circ\text{C}55 ∘C and the result after the mixture is cooled.
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.