Which of the following statements apply to enzymes?
I, III and IV
I, II and III
I and IV
II and III
The following diagram shows the three stages involved in enzyme catalysis.
Which of the following provides the most accurate description of the events occurring at each stage?
| 1 | 2 | 3 | |
| A. | The substrate collides with the enzyme | New bonds are forming within the substrate molecule | Chemical substances are released from the enzyme |
| B. | The substrate collides with the active site of the enzyme | The substrate is bound to the active site of the enzyme | The products are released from the active site |
| C. | The substrate binds to the enzyme | New chemical substances are formed while attached to the enzyme | These substances are released from the enzyme |
| D. | The substate collides with the active site of the enzyme | The substrate changes into different chemical substances | The products are released from the active site |
An enzyme catalysed reaction is heated to a temperature of 65 °C.
Which of the following best explains the effect this temperature increase would have on the enzymes?
The enzyme and substrate molecules will gain kinetic energy and collide more frequently
The bonds in the enzyme will vibrate more and break, which will cause a permanent change in the shape of the active site
The bonds in the enzyme will vibrate more and break, causing a temporary change in the shape of the active site
The active site of the enzyme will permanently change shape due to the increased speed of collisions between the substrate molecule and the active site
Lactase is an enzyme that is often immobilised and used in the food industry to produce lactose-free milk.
Which of the following would not be an advantage of using lactase?
Increases the sweetness of many dairy products, such as yoghurt and milk shakes
It may increase the rate of crystallisation of frozen dairy products, such as ice cream
It may increase the fermentation rate of products such as yoghurt and cheese
Lactase is able to function closer to its optimum conditions in a controlled factory environment
Students investigated the effect of pH on catalase activity. Each experiment was repeated at a different pH value (pH = 2, 4, 7, 9, 11) and was set up as follows:
Which of the rows in the following table correctly identifies the variables in this experiment?
| Independent variable | Dependent variable | Control variable | |
| A. | pH | Initial reaction rate | Volume of oxygen released |
| B. | Initial reaction rate | pH | Volume of hydrogen peroxide |
| C. | pH | Initial reaction rate | Volume of hydrogen peroxide |
| D. | Volume of oxygen released | pH | Initial reaction rate |
