Anaerobic respiration in yeast cells involves a series of enzyme-controlled reactions that break down sugars, releasing carbon dioxide gas as a waste product. The volume of carbon dioxide released can be monitored to determine the rate of respiration.
A student investigated the effect of temperature on the rate of respiration in a strain of baker's yeast (Saccharomyces cerevisiae). They measured the volume of carbon dioxide gas produced over a period of 16 minutes at 24∘C24^\circ\text{C}24∘C and 29∘C29^\circ\text{C}29∘C using a gas syringe.
Explain why using a gas syringe to collect the gas is more suitable than collecting it over water in an inverted measuring cylinder.
The student's measurements are recorded in the table below:
| Temperature (∘C^\circ\text{C}∘C) | Volume of carbon dioxide gas (cm3\text{cm}^3cm3) released in 16 minutes | ||
|---|---|---|---|
| Trial 1 | Trial 2 | Trial 3 | |
| 24 | 51 | 56 | 52 |
| 29 | 73 | 79 | 76 |
(i) Calculate the mean rate of carbon dioxide gas produced at 24∘C24^\circ\text{C}24∘C in cm3 min−1\text{cm}^3\text{ min}^{-1}cm3 min−1. Give your answer to 1 decimal place. Show your working.
The rate of gas production at 29∘C29^\circ\text{C}29∘C is higher than at 24∘C24^\circ\text{C}24∘C. Use kinetic theory and your knowledge of enzymes to explain why.
Heavy metal ions, such as silver ions (Ag+\text{Ag}^+Ag+), can act as non-competitive inhibitors of key respiratory enzymes by binding to a site away from the active site. Suggest how this inhibits the enzyme's activity.
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.