C1.1. Enzymes and metabolism

The graph shows the activity of an enzyme at different temperatures.

[Source: © International Baccalaureate Organization 2019]

What does the dashed line in the graph represent?

A. Increasing temperature increases substrate concentration.

B. Increasing temperature affects the active site.

C. Increasing temperature increases the rate of reaction.

D. Increasing temperature decreases the movement of particles.

The graph shows the activity of an enzyme at different temperatures.

[Source: © International Baccalaureate Organization 2019]

What does the dashed line in the graph represent?

A. Increasing temperature increases substrate concentration.

B. Increasing temperature affects the active site.

C. Increasing temperature increases the rate of reaction.

D. Increasing temperature decreases the movement of particles.

With reference to the diagram, identify one example of catabolism.

With reference to the diagram, identify one example of catabolism.

With reference to the diagram, identify one example of catabolism.

State a role of the active site of an enzyme.

State a role of the active site of an enzyme.

State a role of the active site of an enzyme.

State a role of the active site of an enzyme.

State a role of the active site of an enzyme.

State a role of the active site of an enzyme.

State a role of the active site of an enzyme.

State a role of the active site of an enzyme.

State a role of the active site of an enzyme.

State a role of the active site of an enzyme.

State a role of the active site of an enzyme.

State a role of the active site of an enzyme.

The graph of the effect of pH on immobilized lipase activity does not allow for the determination of optimum pH precisely. Explain how a more exact value for the optimum pH could be determined.

The graph shows the results of an investigation into the activity of turnip peroxidase. The accumulation of the product of the reaction catalysed by the enzyme is shown at different pH values.

[Source: © International Baccalaureate Organization 2019]

Based on the data in the graph, what is most probably the optimum pH for turnip peroxidase?

A. Between 3 and 5

B. Between 10 and 11

C. Between 7 and 8

D. Between 9 and 10

Explain the decrease in activity of the enzyme on either side of the optimum temperature.

Outline, using graphs, the effect of different factors that influence enzyme activity.

Outline one factor that could affect the activity of Rubisco.

The activity of amylase from two bacterial species and a fungus was measured at different pH levels and constant temperature. The results are shown in the graph.

[Source: Held, P., 2012. Enzymatic Digestion of Polysaccharides. Part II: Optimization of Polymer Digestion and Glucose Production in Microplates. Available at: https://www.agilent.com/cs/library/applications/enzymatic-digestion-of-polysaccharides-part-II-5994-3304EN-agilent.pdf.]

Which statement about the effect of pH on amylase can be concluded?

A.  A. oryzae amylase has the highest optimum pH.

B.  A change in pH affects amylase most in B. licheniformis.

C.  The optimum pH is 6 in B. subtilis.

D.  Amylase activity at pH 8 is the lowest in B. licheniformis.

Explain how temperature affects enzymes.

State the effect that immobilizing the enzyme had on the relative activity of the enzyme.

Using the information in the graph, describe how the experiment could be extended to determine the optimum temperature for immobilized HRP.

State the purpose of lime water in flask B.

Identify the independent variable.

In the grass plant Halopyrum mucronatum, the enzyme amylase breaks bonds in polysaccharides during germination. The graph shows how the activity of the enzyme varies with the concentration of polysaccharide.

_{[Source: Material from: Siddiqui, Z.S. and Khan, M.A., The role of enzyme amylase in two germinating seed morphs of
Halopyrum mucronatum (L.) Stapf. in saline and non-saline environment, published 2011, Acta Physiologiae
Plantarum, reproduced with permission of SNCSC.]}

What is the reason for the curve levelling off?

A.  There is insufficient substrate for the enzyme to act on.

B.  The product acts as an enzyme inhibitor.

C.  The enzymes have all been consumed in the reaction.

D.  All the enzyme active sites are occupied by substrate.

In the grass plant Halopyrum mucronatum, the enzyme amylase breaks bonds in polysaccharides during germination. The graph shows how the activity of the enzyme varies with the concentration of polysaccharide.

_{[Source: Material from: Siddiqui, Z.S. and Khan, M.A., The role of enzyme amylase in two germinating seed morphs of
Halopyrum mucronatum (L.) Stapf. in saline and non-saline environment, published 2011, Acta Physiologiae
Plantarum, reproduced with permission of SNCSC.]}

What is the reason for the curve levelling off?

A.  There is insufficient substrate for the enzyme to act on.

B.  The product acts as an enzyme inhibitor.

C.  The enzymes have all been consumed in the reaction.

D.  All the enzyme active sites are occupied by substrate.

The graph of the effect of pH on immobilized lipase activity does not allow for the determination of optimum pH precisely. Explain how a more exact value for the optimum pH could be determined.

The graph shows the results of an investigation into the activity of turnip peroxidase. The accumulation of the product of the reaction catalysed by the enzyme is shown at different pH values.

[Source: © International Baccalaureate Organization 2019]

Based on the data in the graph, what is most probably the optimum pH for turnip peroxidase?

A. Between 3 and 5

B. Between 10 and 11

C. Between 7 and 8

D. Between 9 and 10

Explain the decrease in activity of the enzyme on either side of the optimum temperature.

Explain the decrease in activity of the enzyme on either side of the optimum temperature.

Outline, using graphs, the effect of different factors that influence enzyme activity.

Outline, using graphs, the effect of different factors that influence enzyme activity.

Outline one factor that could affect the activity of Rubisco.

Outline one factor that could affect the activity of Rubisco.

The activity of amylase from two bacterial species and a fungus was measured at different pH levels and constant temperature. The results are shown in the graph.

[Source: Held, P., 2012. Enzymatic Digestion of Polysaccharides. Part II: Optimization of Polymer Digestion and Glucose Production in Microplates. Available at: https://www.agilent.com/cs/library/applications/enzymatic-digestion-of-polysaccharides-part-II-5994-3304EN-agilent.pdf.]

Which statement about the effect of pH on amylase can be concluded?

A.  A. oryzae amylase has the highest optimum pH.

B.  A change in pH affects amylase most in B. licheniformis.

C.  The optimum pH is 6 in B. subtilis.

D.  Amylase activity at pH 8 is the lowest in B. licheniformis.

Explain how temperature affects enzymes.

Explain how temperature affects enzymes.

State the effect that immobilizing the enzyme had on the relative activity of the enzyme.

Using the information in the graph, describe how the experiment could be extended to determine the optimum temperature for immobilized HRP.

State the purpose of lime water in flask B.

Identify the independent variable.

In the grass plant Halopyrum mucronatum, the enzyme amylase breaks bonds in polysaccharides during germination. The graph shows how the activity of the enzyme varies with the concentration of polysaccharide.

_{[Source: Material from: Siddiqui, Z.S. and Khan, M.A., The role of enzyme amylase in two germinating seed morphs of
Halopyrum mucronatum (L.) Stapf. in saline and non-saline environment, published 2011, Acta Physiologiae
Plantarum, reproduced with permission of SNCSC.]}

What is the reason for the curve levelling off?

A.  There is insufficient substrate for the enzyme to act on.

B.  The product acts as an enzyme inhibitor.

C.  The enzymes have all been consumed in the reaction.

D.  All the enzyme active sites are occupied by substrate.

In the grass plant Halopyrum mucronatum, the enzyme amylase breaks bonds in polysaccharides during germination. The graph shows how the activity of the enzyme varies with the concentration of polysaccharide.

_{[Source: Material from: Siddiqui, Z.S. and Khan, M.A., The role of enzyme amylase in two germinating seed morphs of
Halopyrum mucronatum (L.) Stapf. in saline and non-saline environment, published 2011, Acta Physiologiae
Plantarum, reproduced with permission of SNCSC.]}

What is the reason for the curve levelling off?

A.  There is insufficient substrate for the enzyme to act on.

B.  The product acts as an enzyme inhibitor.

C.  The enzymes have all been consumed in the reaction.

D.  All the enzyme active sites are occupied by substrate.

Predict what effect arginase has on the activation energy of this reaction.

Predict what effect arginase has on the activation energy of this reaction.

Predict what effect arginase has on the activation energy of this reaction.

The first enzyme in the metabolic pathway that produces isoleucine is threonine deaminase. Which graph illustrates the relationship between threonine deaminase activity and threonine concentration?

[Source: © International Baccalaureate Organization 2019]

The first enzyme in the metabolic pathway that produces isoleucine is threonine deaminase. Which graph illustrates the relationship between threonine deaminase activity and threonine concentration?

[Source: © International Baccalaureate Organization 2019]

Explain the role of lactose in the expression of the gene for lactase production.

Explain the role of lactose in the expression of the gene for lactase production.

Explain the role of lactose in the expression of the gene for lactase production.

The grey line in each of the graphs below represents the rate of reaction catalysed by an uninhibited enzyme as substrate concentration is increased.

Which graph shows expected results if a competitive inhibitor was added to the reaction?

[Source: © International Baccalaureate Organization 2019]

Distinguish between competitive and non-competitive enzyme inhibition.

The grey line in each of the graphs below represents the rate of reaction catalysed by an uninhibited enzyme as substrate concentration is increased.

Which graph shows expected results if a competitive inhibitor was added to the reaction?

[Source: © International Baccalaureate Organization 2019]

Distinguish between competitive and non-competitive enzyme inhibition.

Distinguish between competitive and non-competitive enzyme inhibition.

Some bacteria can synthesize the amino acid isoleucine from threonine, a process involving five enzymes (E₁ to E₅) and four intermediary products (P, Q, R and S). The production of isoleucine is controlled by end-product inhibition.

Which statement describes this end-product inhibition?

A. If isoleucine accumulates, it inhibits the production of P.

B. End-product inhibition causes a build-up of intermediary products.

C. Isoleucine inhibits E₅, so no more isoleucine is produced.

D. Isoleucine affects the structure of threonine.

Distinguish between competitive and non-competitive enzyme inhibition.

Explain the regulation of metabolic pathways by end-product inhibition.

Through a series of enzymatic reactions, the amino acid threonine is converted to isoleucine. The graph shows the rate of reaction of threonine deaminase according to the concentration of its substrate threonine, with and without the presence of isoleucine.

^{[Source: Calhoun, D.H., Rimernian, R.A. and Hatfield, G.W., 1973.
Threonine Deaminase from Escherichia coli.
I. Purification and Properties. The Journal Of Biological Chemistry,
248(10), pp. 3511–3516. Open Access.]}

What can be seen from these results?

A.  Threonine deaminase only works in the presence of isoleucine.

B.  Isoleucine inhibits threonine deaminase at low concentrations of threonine.

C.  Production of isoleucine is inhibited at high concentration of threonine.

D.  End-product inhibition controls the production of threonine deaminase.

Some bacteria can synthesize the amino acid isoleucine from threonine, a process involving five enzymes (E₁ to E₅) and four intermediary products (P, Q, R and S). The production of isoleucine is controlled by end-product inhibition.

Which statement describes this end-product inhibition?

A. If isoleucine accumulates, it inhibits the production of P.

B. End-product inhibition causes a build-up of intermediary products.

C. Isoleucine inhibits E₅, so no more isoleucine is produced.

D. Isoleucine affects the structure of threonine.

Distinguish between competitive and non-competitive enzyme inhibition.

Distinguish between competitive and non-competitive enzyme inhibition.

Explain the regulation of metabolic pathways by end-product inhibition.

Explain the regulation of metabolic pathways by end-product inhibition.

Through a series of enzymatic reactions, the amino acid threonine is converted to isoleucine. The graph shows the rate of reaction of threonine deaminase according to the concentration of its substrate threonine, with and without the presence of isoleucine.

^{[Source: Calhoun, D.H., Rimernian, R.A. and Hatfield, G.W., 1973.
Threonine Deaminase from Escherichia coli.
I. Purification and Properties. The Journal Of Biological Chemistry,
248(10), pp. 3511–3516. Open Access.]}

What can be seen from these results?

A.  Threonine deaminase only works in the presence of isoleucine.

B.  Isoleucine inhibits threonine deaminase at low concentrations of threonine.

C.  Production of isoleucine is inhibited at high concentration of threonine.

D.  End-product inhibition controls the production of threonine deaminase.

Distinguish between competitive and non-competitive enzyme inhibition.

Distinguish between competitive and non-competitive enzyme inhibition.

Distinguish between competitive and non-competitive enzyme inhibition.