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DP IB Biology: SL

Topic Questions

Home / IB / Biology: SL / DP / Topic Questions / 1. Cell Biology / 1.1 Cells: Theory / Structured Questions: Paper 2


1.1 Cells: Theory

Question 1a

Marks: 2
a)

Pseudonaja textilis (Eastern Brown Snake) has a group of specialised chemoreceptors located in the Jacobson’s organ, which is on the roof of the snake's mouth. It also has venom glands that produce a neurotoxin.

These are essential in allowing the snake to detect and paralyse its prey.

Explain the property described in this passage that allows multicellular organisms to function efficiently. 

[2 marks]

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    Key Concepts
    Emergent Properties

    Question 1b

    Marks: 2
    b)

    The Jacobson’s organ in Pseudonaja textilis (Eastern Brown Snake) is a pair of crescent-shaped chambers where odour molecules are deposited by the forked tongue when it retracts back into the mouth.

    1-1-h-1b-paper-2

    Suggest why Jacobson’s organ is crescent-shaped.

    [2 marks]

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      Question 1c

      Marks: 2
      c)

      Scientists studying the expression of olfactory receptor (OR) genes in four snake species found that fewer than 3% were non-functional genes compared to humans who have up to 67% non-functioning OR genes. These genes code for olfactory receptor proteins located in the cilia of the nostrils.

      Deduce why the expression of certain genes, like the OR gene in nostrils, is beneficial to multicellular organisms.

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        Question 2a

        Marks: 2
        a)

        Creutzfeldt-Jakob disease is a rare neurodegenerative disease caused by abnormally-folded proteins found in the brain. Proteins that trigger abnormal folding are called prions.

        Suggest why scientists have not classified prions as living.

        [2 marks]

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          Key Concepts
          Cell Theory

          Question 2b

          Marks: 2
          b)

          Viruses and viroids are two other particles that are not considered to be living entities. These are considered exceptions to the cell theory. 

          Discuss two other discrepancies to cell theory that scientists have discovered.

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            Key Concepts
            Cell Theory

            Question 2c

            Marks: 3
            c)

            Euglena gracilis is a unicellular eukaryotic organism that inhabits moist soils and stagnant fresh water, often forming green scum on the surface of ponds and lakes.

            E. gracilis are heterotrophic and autotrophic, and propel themselves using a flagellum. They have an eyespot which allows them to respond to sunlight and contractile vacuoles that regulate the composition of the cytoplasm.

            Compare the functions of life of E.gracilis and a Paramecium species.

            [3 marks]

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              Key Concepts
              Functions of Life

              Question 3a

              Marks: 3
              a)

              A plant palisade mesophyll cell is 4 μm in width and depth, and 25 μm in length.

              Its shape is approximately cuboid. 

              Calculate the surface area to volume ratio of this cell. Show your working.

              [3 marks]

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                Question 3b

                Marks: 3
                b)
                If the palisade cell in part (a) has a large central vacuole, so that the cytoplasm (not including the vacuole) extends inward 500 nm from the plasma membrane of the cell. 
                    
                Calculate the surface area to cytoplasmic volume ratio. Show your working.

                [3 marks]

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                  Question 3c

                  Marks: 2
                  c)

                  From part (b) comment on what the function of the plant vacuole is. 

                  [2 marks]

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                    Question 4a

                    Marks: 4
                    a)

                    The image below is a photomicrograph of a transverse section through part of a stem.

                    6Z9U726T_plant_stem_255_07_cross-section_of_stem_of_aristolochia

                    Doc. RNDr. Josef Reischig, CSc., CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons

                    Draw a large tissue plan diagram of this part of the stem.

                    [4 marks]

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                      Question 4b

                      Marks: 2
                      b)

                      A student used a light microscope to study the plant stem pictured in part (a). The diagram below shows the stage micrometer scale that was used to calibrate an eyepiece graticule. 

                      One division, on either the stage micrometer scale or the eyepiece graticule, is the distance between two adjacent lines. 

                      The length of one division on this stage micrometer is 0.01 mm.

                      1-1-h-4b-paper-21

                      Using this stage micrometer, calculate the actual length of one eyepiece graticule division. Show your working.

                      [2 marks]

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                        Question 4c

                        Marks: 1
                        c)
                        The photomicrograph below was taken using the same microscope with the same lenses as part (b).
                        The same eyepiece graticule was also used; a section of that graticule is shown under the image below.
                         
                        distance-graticule
                        Use the calibration of the eyepiece graticule unit from part (b) and the information in the photomicrograph to estimate the actual length in μm of the plant tissue from A to B

                        [1 mark]

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                          Question 5a

                          Marks: 3
                          One mark is available for clarity of communication throughout this question.



                          a)
                          Explain the importance of the surface area to volume ratio to a growing bacterial cell.

                          [3 marks]

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                            Question 5b

                            Marks: 7
                            b)
                            Evaluate two named therapeutic uses of stem cells.

                            [7 marks]

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                              Question 5c

                              Marks: 5
                              c)
                              Compare and contrast the functions of life in a Paramecium with a named photosynthesising organism.

                              [5 marks]

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