1 markMost human biological reactions require a catalyst.
Which of the following are functions of enzymes?
Enzymes cannot act on more than one substrate
Enzymes can catalyse chemical reactions
Enzymes can increase the activation energy
Enzymes can only catalyse one chemical reaction
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1 markWhich of the following factors can denature an enzyme?
Enzyme concentration
Inhibitors
Substrate concentration
Temperature and pH
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1 markWhich of the following statements is true regarding enzyme specificity?
Enzymes are not affected by the shape of the substrate
Enzymes can bind to any molecule they encounter
Enzymes can catalyse a wide range of different reactions
Enzymes can only bind to one specific substrate
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1 markWhat is the role of coenzymes in enzyme-catalysed reactions?
Act as substrates for the enzyme
Carry electrons or chemical groups between enzymes
Facilitate the binding of the enzyme to another enzyme
Inhibit enzyme activity
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1 markWhich of the following statements is true regarding competitive inhibition?
| 1 | It cannot be reversed |
| 2 | Inhibitor does not need to resemble substrate |
| 3 | The rate of the reaction is slowed down |
1, 2 and 3
Only 1 and 2
Only 2 and 3
Only 3
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1 markWhich of the following options is an intracellular process controlled by enzymes?
Digestion of a pathogen inside a phagolysosome
Hydrolysis of starch into simple sugars
Digestion of wood by hyphae of fungi
Conversion of fibrinogen to fibrin during blood clotting.
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1 markAn investigation into the activity of catalase on liver tissue at different temperatures was completed with the volume of oxygen collected measured at different time intervals as an indication of catalase activity.
The table below shows the results with the mean rate of reaction at each temperature calculated:
| Temperature (oC) | Mean rate of reaction (cm3s-1) |
| 0 | 0 |
| 10 | 0.21 |
| 20 | 0.44 |
| 30 | 0.86 |
| 40 | 1.69 |
| 50 | 1.32 |
What is the correct calculated temperature coefficient (Q10) for the reaction between 20 oC and 30 oC.
0.38
0.51
1.95
2.02
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1 markIngestion of methanol can lead to irreversible visual impairment or blindness. Poisoning is caused by the products produced when methanol is broken down by alcohol dehydrogenase, which include formaldehyde.
Ethanol is also oxidised by alcohol dehydrogenase.
Which of the following statements explains why ethanol is often used as a treatment for methanol poisoning?
Ethanol acts as a competitive inhibitor and binds to the active site of alcohol dehydrogenase.
Ethanol acts as a non-competitive inhibitor and changes the tertiary structure of alcohol dehydrogenase.
Ethanol breaks methanol down into safe products.
The products of the breakdown of ethanol by alcohol dehydrogenase act as end-product inhibitors.
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1 markVitamins B2 and B3 are fundamental in the production of NAD and FAD which have an important role in some of the stages of respiration.
Which of the following statements explain why it is recommended that patients suffering from fatigue take these vitamins as supplements?
NAD and FAD are coenzymes that carry electrons to the electron transport chain.
NAD and FAD are cofactors that stabilise the structure of ATP synthase.
NAD and FAD are inhibitors that reduce the activity of the Kreb’s cycle.
NAD and FAD are prosthetic groups that help to form the structure of ATP synthase.
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1 markThe following graph shows a mammalian enzyme reaction taking place at different temperatures.
Which of the following statements does not explain the differences in the shapes of the curves at different temperatures?
At 65oC there were more successful collisions.
The curve at 37oC levels off as the enzyme denatures.
At 20oC the reaction was not completed in 60 minutes.
The initial rate of reaction at 37oC was slower to begin with than at 65oC.
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1 markWhich of the following, A to D, is true of a competitive enzyme inhibitor?
binds to a site other than the active site
can bind irreversibly to the active site
changes the shape of the active site
effects can be overcome by adding more substrate
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1 markThe image below shows a diagram of an enzyme.
Which of the following could be a competitive inhibitor of this enzyme?
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1 markThe following graph shows the rate of reaction of an enzyme in different substrate concentrations.
Which letter, A to D, shows the rate of reaction with a fixed quantity of competitive inhibitor?
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1 markWhich of the following is the prosthetic group for carbonic anhydrase?
Cl-
Zn2+
Vitamin B3
Fe2+
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1 markThe graph below shows how the rate of reaction of the enzyme trypsin changes with temperature.
What is the temperature coefficient, Q10, of this reaction before the enzyme denatures?
0.05
0.39
1.19
1.76
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1 markWhat is the correct definition of the term coenzyme?
A non-protein organic molecule, not permanently attached to an enzyme, but needed to allow the enzyme to function.
A molecule that binds to the enzyme, changing the shape of the active site, preventing an enzyme-substrate complex from forming.
An inorganic ion that forms the centre of a globular protein.
A metal ion that attaches to the enzyme, changing the shape of the active site, increasing the likelihood of a reaction.
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1 markWhich of the graphs, A to D, represents the energy changes involved during an enzyme-controlled catabolic reaction?
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1 markWhich of the following, A to D, is an incorrect statement about enzymes?
Trypsin catalyses intracellular reactions
Catalase catalyses intracellular reactions
Extracellular enzymes are produced inside the cell
Extracellular enzymes work outside the cell
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1 markA student investigated the effect of pH on the rate of an enzyme controlled reaction. The student measured the rate of product formation from the reaction.
What would be a suitable control for this investigation?
An identical tube set up with:
No buffer
No buffer and no enzyme
No enzyme
No substrate
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1 markA student wished to use a starch solution of 0.01% for an enzyme experiment. A stock solution of 1.0% starch solution was provided.
Which of the following dilutions would be the best method to achieve the desired concentration with greatest precision, using standard laboratory equipment?
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