Fermentation involves enzymes that break down sugar, releasing carbon dioxide gas. The volume of gas released can be used to measure the rate of fermentation.
A student investigates how temperature affects the rate of fermentation in yeast. They measure the volume of carbon dioxide released over 15 minutes at 30∘C30^\circ\text{C}30∘C and 35∘C35^\circ\text{C}35∘C using a gas syringe.
Explain why using a gas syringe to collect the gas is better than collecting it over water in a measuring cylinder.
The student's results are shown in the table below:
| Temperature (∘C^\circ\text{C}∘C) | Volume of carbon dioxide gas (cm3\text{cm}^3cm3) released in 15 minutes | ||
|---|---|---|---|
| Trial 1 | Trial 2 | Trial 3 | |
| 30 | 38 | 41 | 41 |
| 35 | 51 | 47 | 52 |
Calculate the mean rate of gas produced at 30∘C30^\circ\text{C}30∘C in cm3/minute\text{cm}^3/\text{minute}cm3/minute. Give your answer to 1 decimal place. Show your working.
The rate of gas produced at 35∘C35^\circ\text{C}35∘C is greater than at 30∘C30^\circ\text{C}30∘C. Use ideas about enzymes and kinetic theory to explain why.
Heavy metal ions can act as non-competitive inhibitors by binding to a site on the enzyme away from the active site. Suggest how this inhibits the enzyme.
72 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.