Syllabus Edition

First teaching 2014

Last exams 2024

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Metabolism (DP IB Biology: HL)

Exam Questions

3 hours35 questions
1
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1 mark

Which 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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2
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1 mark

The following statements are about enzymes:

  1. The speed that they function at can be reduced by competitive inhibitors.
  2. Their primary structure is translated from mRNA.
  3. They can be embedded in the plasma membrane of a cell.
  4. They all have quaternary structures.

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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3
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1 mark

Which of the following sketch graphs best shows the effect of an enzyme on a biochemical reaction profile?

  • gxd3xaCX_8-1_q3_ae

  • KOoPh84M_8-1_q3_be

  • hUYQH2fc_8-1_q3_ce

  • WMB3Gxz8_8-1_q3_de

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4
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1 mark

Which one of the following phenomena is not a consequence of end-product inhibition in biochemical pathways?

  • Regulation of the pathway.

  • Prevention of a build-up of biochemical intermediate compounds.

  • Shutdown of the pathway once product levels reach zero. 

  • Allosteric changes to an enzyme involved in the pathway.

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5
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1 mark

Enzymes 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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11 mark

Which of the following statements about metabolism are correct?

  1. Metabolism involves chemicals called metabolites.
  2. Metabolism involves reactions in a linear chain.
  3. Metabolism involves reactions in a cycle.
  4. Metabolism involves only the breakdown of molecules.
  • I and IV only

  • II and III

  • All of the statements

  • I, II and III 

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21 mark

Which of the following is not a correct description of the “transition state” in enzyme-controlled reactions?

  • The enzyme-substrate complex, prior to the products being formed, can be said to be in the transition state.

  • The enzyme-product complex, prior to the products being released, can be said to be in the transition state.

  • The transition state occurs when a substrate binds to the enzyme’s active site.

  • Transition state is a temporary state 

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31 mark

The graph below shows the energy changes during a reaction.q3_8-1_metabolism_ib_biology_hl_mcq

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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41 mark

What is the difference between a competitive and non-competitive inhibitor?

 

Competitive inhibitor

Non-competitive inhibitor

A

Interferes with active site

Interferes with an alternative site

B

Interferes with an alternative site

Interferes with the active site

C

Changes the active site

Changes the substrate

D

Changes the substrate

Changes the active site

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    51 mark

    Cyanide ions are an example of an allosteric inhibitor that targets the enzyme cytochrome c oxidase in aerobic respiration.

    Which row best describes the action of cyanide ions?

     

    Can bind to an alternative site

    Can bind to the active site

    A

    Yes

    Yes

    B

    Yes

    No

    C

    No

    Yes

    D

    No

    No

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      61 mark

      Isoleucine can be described as an end-product inhibitor.

      Which statement best describes the action of isoleucine?

      • It acts as a competitive inhibitor to threonine and it binds to an allosteric site on threonine deaminase.  

      • It acts as a competitive inhibitor to threonine and it binds to the active site on threonine deaminase.

      • It acts as a non-competitive inhibitor to threonine and it binds to an active site on threonine deaminase.

      • It acts as a non-competitive inhibitor to threonine and it binds to an allosteric site on threonine deaminase.

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      71 mark

      The protein sequence of an enzyme involved in the Plasmodium parasite’s metabolism has been identified in order to support research into anti-malarial drugs.

      Which terms best fill the gaps in the sentence about Plasmodium parasite research below?         

      Bioinformatics can be used to screen ………I……….. against a database of chemicals to identify potential ………II………..

       

      I

      II

      A

      Enzymes

      Enzyme inhibitors

      B

      Proteomes

      Products

      C

      Enzymes

      Active sites

      D

      Proteomes

      Substrates

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        81 mark

        Which graph shows the rate of a reaction taking place in the presence of a competitive inhibitor compared to the rate of a reaction in the absence of an inhibitor?q8_8-1_metabolism_ib_biology_hl_mcq

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          91 mark

          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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          101 mark

          Which statement best describes how to calculate the initial rate of a reaction from a graph such as the one below?ma10_8-1_metabolism_ib_biology_hl_mcq

          • 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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          1
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          1 mark

          This diagram shows a metabolic pathway occurring in an organelle. The speed of this metabolic pathway is self-regulating as the end product acts as a competitive inhibitor to enzyme 2. 

            enzyme 1   enzyme 2   enzyme 3  
          reactant intermediate X intermediate Y end product

          What would you expect not to occur when adding an additional end product to the organelle?

          • Enzyme 2's activity will decrease

          • The amount of intermediate Y would decrease

          • The amount of reactant would increase

          • The amount of intermediate X would increase

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          2
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          1 mark

          In the graph, Z represents the relationship between the initial rate of an enzyme-catalysed reaction and the concentration of its substrate under optimal conditions and without an inhibitor.8-1_q2h

          Which curve would represent the same experiment carried out in the presence of a low concentration of a non-competitive inhibitor?

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            3
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            1 mark

            The 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?

            • 8-1_q3_ah

            • 8-1_q3_bh

            • 8-1_q3_ch

            • 8-1_q3_dh

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            4
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            1 mark

            The following six statements are steps in using bioinformatics to find potential cures for malaria, one of the most serious infectious diseases that humans face. The steps are not listed in the correct order below. 

            1. Computer modelling of candidate molecules to identify strong candidates

            2. Determining the malaria parasite's proteome

            3. Identifying candidate molecules that could inhibit malaria parasite enzymes

            4. Sequencing the malaria parasite's genome

            5. Drug trials to establish safety and efficacy 

            6. Identification of malaria parasite enzymes that could be targets

            Which of A - D places the statements into chronological order?

            • 4 → 2 → 6 → 3 → 1 → 5

            • 2 → 4 → 3 → 5 → 6 → 1

            • 4 → 2 → 3 → 5 → 1 → 6

            • 2 → 6 → 4 → 5 → 3 → 1

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            5
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            1 mark

            The 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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