Pupil sheet · Enzymes
Enzymes — final check
Name ______________________ Date ____________
Work alone, with the lesson closed. Answer every question; there are no hints.
1. explain
Sucrase is an enzyme that breaks down sucrose into glucose and fructose. Explain how sucrase does this. Use the terms active site, substrate, enzyme–substrate complex and products.
2. describe / explain
(a) Describe what a catalyst is. (b) Explain why living organisms could not survive without enzymes.
(a) A catalyst
(b) Why enzymes are needed
3. explain
A protease from the stomach breaks down the protein in egg white, but it does not break down the starch in bread. Explain why.
4. state / describe
State what enzymes are made of, and describe their role in the chemical reactions of an organism.
5. calculate / describe
Amylase was tested at five temperatures. Time of the first orange-brown drop at each temperature: 15 °C: 240 s; 25 °C: 120 s; 35 °C: 60 s; 45 °C: 90 s; 60 °C: no end point within 5 minutes. (a) Calculate the relative rate at 25 °C, to one decimal place. (b) State the best tested temperature. (c) Describe the effect of temperature on the rate.
(a) Relative rate at 25 °C (no unit): ______________ unit ________
(b) Best tested temperature: ______________ unit ________
(c) Describe the effect of temperature on the rate
6. explain
Explain why the rate of an enzyme reaction falls when the temperature rises above the optimum. Use the ideas of shape, fit and denaturation.
7. suggest
In the amylase investigation, the end point at 40 °C was recorded as 60 s, because the drop at 30 s was still purple. Suggest two ways to make the result for 40 °C more precise and more reliable.
8. explain
A protease from the stomach breaks down protein quickly at pH 2, but hardly at all at pH 7. Explain this, using the ideas of shape, fit and denaturation.
9. calculate / identify
Amylase at 40 °C with buffers. Time of the first orange-brown drop with each buffer: pH 5: 150 s; pH 6: 90 s; pH 7: 60 s; pH 8: 120 s. (a) Calculate the relative rate at pH 6, to one decimal place. (b) State the best tested pH.
(a) Relative rate at pH 6 (no unit): ______________ unit ________
(b) Best tested pH: ______________ unit ________