Syllabus Edition
First teaching 2023
First exams 2025
Which of the options below refers to the features of catabolism?
E xergonic, condensation reaction, an example is polypeptide synthesis
Endergonic, hydrolysis reaction, an example is respiration
Endergonic, condensation reaction, an example is photosynthesis
Exergonic, hydrolysis reaction, an example is deamination
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1 markWhich of the following statements apply to enzymes?
I, III and IV
I, II and III
I and IV
II and III
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1 markAn 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
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1 markWhich of the following statements is not true about enzymes in metabolic pathways?
All metabolic reactions are catalysed by an enzyme.
All proteins are enzymes.
All enzymes are proteins.
All enzymes reduce activation energy of metabolic reactions in living organisms.
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1 markThe following statements are about enzymes:
Which of these statements are correct for all enzymes?
1 and 3 only
1, 2 and 3 only
2, 3 and 4 only
All of them are correct
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1 markWhich of the following sketch graphs best shows the effect of an enzyme on a biochemical reaction profile?
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1 markEnzymes alter the activation energy required for a biochemical reaction to take place. Which of the following gives the best definition of activation energy?
The energy input required to break bonds in order for a reaction to take place.
The energy is released as bonds breaks in a reaction.
The energy required to allow substrates and enzymes to be closely aligned at the active site.
The energy given off when an enzyme-substrate complex forms.
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1 markThe activity of two types of protease enzymes was measured in two different species of fish; species X and species Y. Protease enzymes are responsible for breaking down proteins into amino acids. The results of the research are shown in the graph.
The unit U denotes the enzyme required for the production of 1 μmol of product per minute. The bars represent the standard deviation.
Which statement about protease enzymes is correct?
The activity of the stomach protease of species Y is 2.5 times greater than that of species X.
The activity of the intestinal protease of species X is significantly higher than the stomach protease of species X.
The activity of the stomach protease of species X is 3.5 times less than that of species Y.
The activity of the intestinal proteases of both species X and Y are significantly higher than the stomach proteases.
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1 markThe following graph shows the change in energy that occurs during an enzyme catalysed reaction.
Which of the following would be the most accurate description of this graph?
This is an anabolic reaction that releases energy. Large, complex molecules are broken down into smaller, simpler ones during hydrolysis reactions.
This is a catabolic reaction that releases energy. Large, complex molecules are broken down into smaller, simpler ones during hydrolysis reactions.
This is an anabolic reaction that requires an input of energy. Large, complex molecules are formed from smaller, simpler ones during condensation reactions.
This is an catabolic reaction that requires an input of energy. Large, complex molecules are formed from smaller, simpler ones during condensation reactions.
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1 markBeetroot (Beta vulgaris) is a root vegetable with a characteristic red colour that is due to the pigment betanin found within the vacuoles of beetroot cells.
Scientists investigated the effect of temperature on the release of betanin from the beetroot cells. This was recorded as the mean absorbance when using a colorimeter, with a higher absorbance indicating more pigment released. The scientists deduced that the pigment is released when the membrane proteins of the tonoplast surrounding the vacuole denature.
The graph below shows their results.
Which of the following descriptions would best explain the point where enzymes start to denature inside the beetroot cells?
Enzymes would denature at 30°C. At this point, the amount of pigment released from the beetroot cells is increasing and this indicates denaturing of the membrane proteins of the vacuole
Enzymes would denature when the temperature inside the beetroot cells increase to above 40°C. This is the point when membrane proteins begin to denature and release more pigment
The enzymes inside the beetroot cells would start to denature at 50°C. The greatest amount of pigment is released from the cells at this point which indicates that the membrane proteins of the vacuole are fully denatured
At temperatures above 60°C, the enzymes inside the beetroot cells will be denatured. Most of the pigment has been released at this point, indicating that the membrane proteins of the vacuole are denatured
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1 markScientists extracted enzymes from different parts of the digestive tract of a mammal. The containers of enzyme samples got mixed up with each other before the scientists could label them. In order to identify the enzymes, they monitored the enzyme activity of each sample at different pH levels to determine the optimum pH for each.
The graph below shows the results for two of the samples (X and Y).
Which of the following would be the most valid conclusion that the scientists can draw from these results?
Enzyme X is from the stomach of the mammal since it performs at an optimum when conditions are acidic, while enzyme Y is most likely from the mouth of the mammal where conditions are more neutral
Enzyme X is from the stomach of the mammal since it performs at an optimum when conditions are acidic, while enzyme Y is most likely from the small intestine of the mammal where conditions are more alkaline
Enzyme Y is from the stomach of the mammal since it performs at an optimum when conditions are acidic, while enzyme X is most likely from the small intestine of the mammal where conditions are more alkaline
Enzyme Y is from the mouth of the mammal since it performs at an optimum when conditions are neutral, while enzyme X is most likely from the small intestine of the mammal where conditions are more alkaline
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1 markThe graphs in A - D show the progress of an enzyme-catalysed reaction, measured by the volume of product released from the reaction mixture over time.
Which graph best depicts how a scientist would establish the average rate of reaction over the first minute of the reaction?
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1 markThe enzyme catalase was added to a large volume of hydrogen peroxide solution. The volume of oxygen produced in the first five seconds was measured at 250 cm3.
What is the initial rate of reaction in dm3 min-1 ?
50 dm3 min-1
3 dm3 min-1
0.05 dm3 min-1
3 000 dm3 min-1
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The four statements below are examples of the two types of metabolism, anabolism and catabolism.
Which one of the statements represents a type of metabolism which is different to the other three options?
Deamination of polypeptides to form urea.
Formation of glycosidic bonds between glucose and fructose.
Depletion of fat stores during a period of starvation.
Anaerobic respiration.
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The graph shows the effect of enzyme concentration on the rate of an enzyme-controlled reaction. The substrate concentration is constant.
Which statement about the graph is correct?
Between X and Z, the number of enzyme molecules is limiting.
Between Y and Z, the number of enzyme molecules is limiting.
Between X and Z, the number of substrate molecules is limiting.
Between Y and Z, the number of substrate molecules is limiting.
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The following statements apply to enzyme-catalysed reactions. Which row of the table best describes the sequence of events in an anabolic reaction?
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The graph shows the course of an enzyme-catalysed reaction at 25 °C.
Which statement about the graph is incorrect?
At X the number of available substrate molecules is high.
At X the number of enzyme/substrate complexes is the same as Y.
At Z the number of available substrate molecules is low.
At Y the number of enzyme/substrate complexes is the same as Z.
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When investigating the rate of reaction of the enzyme lipase on the hydrolysis of triglycerides, the pH must be maintained to prevent the lipase denaturing.
Why might fluctuations in pH occur?
The products of hydrolysis will decrease the pH.
Lipase has a very low optimum pH.
The products of hydrolysis will increase the pH.
The water molecules produced as a byproduct of hydrolysis decreases pH.
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The breakdown of hydrogen peroxide to water and oxygen is catalysed by the enzyme catalase. In an investigation into the effect of temperature on the rate of reaction of catalase, mashed liver (which contains catalase) was added to hydrogen peroxide.
What would the independent variable be in this experiment?
The change in mass of the liver after a given time.
The temperature of the solution.
The mass of liver added at the start.
The volume of oxygen produced.
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Which of the following statements about enzymes is not correct?
They can have multiple active sites.
They are composed of one (or more) polypeptide chain(s).
Ester bonds play an important role in maintaining shape.
They catalyse both anabolic and catabolic reactions.
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A 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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Which of the following statements about metabolism are correct?
I and IV only
II and III
All of the statements
I, II and III
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The graph below shows the energy changes during a reaction.
What effect would adding an enzyme have on the energy changes of the reaction?
Reduction in energy at A
Reduction in energy at B
Reduction in energy at C
Reduction in energy at D
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The table below gives information on the rates of several enzyme-catalysed reactions.
|
Rate of reaction / product formed sec⁻¹ |
Enzyme |
|
1.0 x 10⁶ |
Citrate synthase |
|
5.2 x 10³ |
Aconitase |
|
9.2 x 10⁴ |
Fumarase |
|
3.7 x 10⁷ |
Malate dehydrogenase |
Which enzyme catalyses the reaction with the fastest rate of product formation?
Citrate synthase
Aconitase
Fumarase
Malate dehydrogenase
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Which statement best describes how to calculate the initial rate of a reaction from a graph such as the one below?
Draw a tangent that crosses the origin and that corresponds to the first part of the curve, calculate the rate by dividing change in volume by change in time.
Draw a tangent that corresponds to an area part way along the curve, calculate the rate by dividing change in volume by change in time.
Draw a tangent that crosses the origin and that corresponds to the first part of the curve, calculate the rate by dividing change in time by change in volume.
Draw a tangent that corresponds to an area part way along the curve, calculate the rate by dividing change in time by change in volume
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