IBBiologySLExam QuestionsForm & FunctionProteins

Syllabus Edition

First teaching 2023

First exams 2025

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Proteins (SL IB Biology)

Exam Questions

1 hour26 questions

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Proteins

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Proteins

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1
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Which of the following is not a function of proteins?

  • Involved in the formation of the cytoskeleton within a cell that facilitates chromosome movement

  • Act as a store of chemical potential energy in cells

  • Act as chemical messengers that are secreted by glands and act on different parts of the body

  • They may speed up chemical reactions within a cell

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2
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A simple tetrapeptide consists of four amino acids.

How many different combinations of amino acids would be possible for this peptide?

  • 16 000

  • 160 000

  • 1 600 000

  • 16 000 000

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3
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Which of the following are ALL examples of proteins?

  • Rubisco, collagen, amylopectin

  • Amylopectin, collagen, guanine

  • Insulin, amylose, spider silk

  • Rhodopsin, immunoglobulins, rubisco

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4
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Which of the following would represent all the elements that are present in proteins?

2-3easyq5

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    11 mark

    Amino acids consist of oxygen, hydrogen, carbon and nitrogen atoms. The diameter of each atom when bonded to another atom is shown in the table below.

    atom single bond / nm double bond / nm
    O 0.13 -
    H 0.06 0.110
    C 0.154 0.120
    N 0.14 0.134

    Using the figures in the table, the approximate length of one amino acid is 0.7 nm, as shown below.q1-2-3-proteins-medium-ib-hl-biology

    What would be the approximate length of a dipeptide of this amino acid after a condensation reaction has occurred?

    • 1.0 nm 

    • 1.2 nm

    • 1.4 nm

    • 1.6 nm 

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    21 mark

    Which of the following chemical groups does not bond directly with the central carbon of an amino acid?

    • ‒OH

    • ‒NH2

    • ‒COOH

    • ‒H

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    31 mark

    Which of the following causes fibrous polypeptides to be insoluble?

    • They are very long.

    • Their surface has nonpolar amino acids.

    • They are usually structural.

    • They have more than one polypeptide chain.

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    41 mark

    Which row of the table best classifies common proteins with differing numbers of polypeptide chains?

      One polypeptide chain Two polypeptide chains Three polypeptide chains
    A Collagen Insulin Haemoglobin 
    B Lysozyme Insulin Collagen
    C Lysozyme Haemoglobin Insulin
    D Haemoglobin Lysozyme Collagen

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      51 mark

      Which of the following diagrams correctly shows the structure of a dipeptide?

      q8-2-3-proteins-medium-ib-hl-biology

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        1
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        Trypsin is a digestive enzyme found in pancreatic juices that breaks down proteins into polypeptides in the small intestine. The image below represents the three dimensional structure of trypsin.

        2-3hardq2

        Image courtesy of 0fb1d8. Licensed under Creative Commons Attribution-Share Alike 4.0 International license. Reused and distributed under conditions found at: https://creativecommons.org/licenses/by-sa/4.0/deed.en

        Which of the following would be the most accurate description of the conformation of trypsin?

        • It is a functional protein that is folded into a specific shape which is held in position by bonds between the R-groups of neighbouring amino acids, with hydrophilic R-groups facing towards the outside of the molecule

        • It is a functional protein that is folded into a specific shape which is held in position by bonds between the R-groups of neighbouring amino acids, with hydrophobic R-groups facing towards the outside of the molecule

        • It is a structural protein that is folded into a specific shape which is held in position by bonds between the R-groups of repeating amino acids

        • It is a functional protein that is folded into a specific shape which is held in position by bonds between the R-groups of neighbouring amino acids, with hydrophilic R-groups facing towards the inside of the molecule

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        2
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        Rituximab is an example of a therapeutic protein that is used to treat certain types of cancers and autoimmune diseases. It is very sensitive to temperature and pH changes and is typically injected into the bloodstream of patients.

        Which of the following statements would explain why therapeutic proteins, such as rituximab, cannot be taken orally?

        I. The molecule would vibrate so fast once in the stomach that the intermolecular bonds would break

        II. The conformation of the protein will change once in the stomach and it may become non-functional

        III. The protein may become insoluble once in the stomach and form a precipitate due to the breakage of ionic bonds

        IV. Conditions in the stomach will cause the hydrophobic R-groups of the protein to be exposed to the outside of the molecule

        • I and IV

        • I, II and III

        • II and III

        • II, III and IV

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        3
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        The denaturation of three different proteins (P, Q and R) at different temperatures were investigated. The more denatured a protein is, the less stable the molecule becomes. The following graph shows the results of this investigation.

        h-4

        Which of the following would be the most valid conclusion that the scientists can draw from these results?

        • Protein R would be less stable and had a lower rate of denaturation above 70°C compared to protein Q, while protein P was fully denatured by 80°C

        • Protein R would be more stable and had a lower rate of denaturation above 70°C compared to protein Q, while protein P was the least heat tolerant of all the proteins

        • Protein Q would be more stable and had a lower rate of denaturation below 70°C compared to protein R, while protein P was fully denatured by 80°C

        • Protein Q would be less stable and had a higher rate of denaturation below 70°C compared to protein R, while protein P was the least heat tolerant of all the proteins

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