Catalase is an enzyme that breaks down hydrogen peroxide into water and oxygen.
Catalase was added to a solution of hydrogen peroxide and the oxygen produced was collected in a gas syringe.
The total volume of oxygen produced from the start of the reaction was recorded every 10 seconds for 1 minute.
The results are shown in the table.
| time / s | total volume of oxygen produced / |
|---|---|
| 0 | 0 |
| 10 | 22 |
| 20 | 40 |
| 30 | 50 |
| 40 | 55 |
| 50 | 57 |
| 60 | 58 |
What can be concluded from these results?
Options
A The reaction stopped after 60 seconds and no more oxygen was produced.
B The highest rate of oxygen production occurred 10 seconds after the start of the reaction.
C It took more than 20 seconds from the start of the reaction for half of the substrate to be converted to water and oxygen.
D The mean rate of reaction between 20 and 30 seconds was twice the mean rate of reaction between 30 and 40 seconds.
Succinic dehydrogenase is an enzyme that catalyses the conversion of succinate to fumarate in aerobic respiration.
Malonate is a reversible inhibitor of succinic dehydrogenase. Malonate reduces the enzyme’s activity by binding to its active site. Malonate and succinate cannot bind to the active site at the same time.
Which statement describes the effect of malonate on the activity of succinic dehydrogenase?
Options
A In the presence of malonate, can still be reached if the concentration of succinate is increased.
B Malonate has no effect on the .
C In the presence of malonate, can still be reached if the concentration of fumarate is increased.
D Malonate decreases the .
The iodine test and the Benedict’s test were carried out on samples of a starch solution. Amylase was added to another sample of the starch solution and incubated for 10 minutes. The Benedict’s test was then carried out on this sample.
What were the results of the tests?
Options
| iodine test before adding amylase | Benedict’s test before adding amylase | Benedict’s test after adding amylase | |
|---|---|---|---|
| A | ✗ | ✓ | ✓ |
| B | ✓ | ✓ | ✗ |
| C | ✓ | ✗ | ✓ |
| D | ✗ | ✗ | ✗ |
key
✓ = positive result
✗ = negative result
Which statements about the mode of action of an enzyme are correct?
1 Some enzymes have a region on their surface to which the substrate has a complementary shape.
2 Some enzymes and their substrates can change shape slightly as the substrate enters the active site.
3 Enzymes permanently change shape when they react with their substrates to form an enzyme–substrate complex.
Options
A 1, 2 and 3
B 1 and 2 only
C 1 and 3 only
D 2 and 3 only
The graph shows the effect of increasing substrate concentration on the rate of reaction of two enzymes that catalyse reactions with the same substrate.
Which statement is correct?
Options
A Enzyme Q has a higher and a higher affinity for the substrate than enzyme P.
B Enzyme Q has a higher and a lower affinity for the substrate than enzyme P.
C Enzyme Q has a lower and a higher affinity for the substrate than enzyme P.
D Enzyme Q has a lower and a lower affinity for the substrate than enzyme P.
Prokaryotes and eukaryotes use extracellular enzymes.
Extracellular digestive enzymes are found in the external environments of some prokaryotes.
Some prokaryotes are digested by hydrolytic enzymes during phagocytosis by eukaryotic cells.
Which row shows the locations where extracellular enzymes are produced?
Options
| site of production of digestive enzymes used by prokaryotes | site of production of hydrolytic enzymes used by eukaryotic phagocytes | |
|---|---|---|
| A | inside cells | inside cells |
| B | inside cells | outside cells |
| C | outside cells | inside cells |
| D | outside cells | outside cells |
Amylase breaks down starch molecules.
Which substance will have the same number of molecules for the duration of this reaction?
Options
A amylase
B water
C maltose
D amylose
Which graphs could show the effect of pH on the rate of enzyme-catalysed reactions?
Options
A 1 and 2
B 1 and 3
C 2 and 4
D 3 and 4
After a heart attack, the enzyme lactate dehydrogenase leaks into the blood plasma from damaged heart muscle.
What is required to measure the activity of lactate dehydrogenase activity in a sample of blood plasma?
| sterilisation of blood plasma by heating | incubation of sample with substrate for lactate dehydrogenase | incubation of sample with lactate dehydrogenase inhibitor | |
|---|---|---|---|
| A | ✓ | ✓ | ✓ |
| B | ✗ | ✓ | ✓ |
| C | ✗ | ✓ | ✗ |
| D | ✗ | ✗ | ✓ |
key
✓ = required
✗ = not required
Options
A row A
B row B
C row C
D row D