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DP IB Biology: SL

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Home / IB / Biology: SL / DP / Topic Questions / 2. Molecular Biology / 2.2 Carbohydrates & Lipids / Structured Questions: Paper 2


2.2 Carbohydrates & Lipids

Question 1a

Marks: 2
a)

The following diagram shows the structure of a polysaccharide found in plant cells.

gj15wkVE_h-1a

i)

Identify the polysaccharide pictured in the diagram.

[1 mark]

ii)
Explain your answer at part i).

[1 mark]

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    Key Concepts
    Formation of Sugars

    Question 1b

    Marks: 2
    b)

    Molecular visualisation software such as Jmol can be used to depict biological molecules. h-1b

    Identify the molecule in this Jmol visualisation. 

    [2 marks]

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      Question 1c

      Marks: 2
      c)

      Three molecules of the same monosaccharide are joined into a trisaccharide. 

      The molecular formula of the monosaccharide is C5H10O5.

      Deduce the formula of the resulting trisaccharide. 

      [2 marks]

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        Key Concepts
        Formation of Sugars

        Question 1d

        Marks: 2
        d)

        The tetrasaccharide stachyose has the molecular formula C24H42O21.

        Describe two aspects of its molecular formula that identifies stachyose as a carbohydrate.

        [2 marks]

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          Key Concepts
          Formation of Sugars

          Question 1e

          Marks: 2
          e)

          A disaccharide has the formula C12H22O11

          It is made up of two identical monosaccharides. 

          Deduce the formula of the monosaccharides that form the disaccharide.

          [2 marks]

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            Key Concepts
            Formation of Sugars

            Question 2a

            Marks: 2
            a)

            Draw a molecular diagram of a 10-carbon saturated fatty acid.

            [2 marks]

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              Question 2b

              Marks: 2
              b)

              Explain why unsaturated fatty acids form different shaped-triglycerides whereas saturated fatty acids do not. 

              [2 marks]

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                Question 2c

                Marks: 2
                c)

                Below is a typical label printed on a piece of food packaging.

                Q2ymu_rG_h-2c

                The product in question is a cookie-style snack food, sold in small packets with see-through plastic packaging. 

                Suggest and explain one aesthetic reason why a food company might wish to market such a food product despite its high saturated fat content. 

                [2 marks]

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                  Question 2d

                  Marks: 2
                  d)

                  Doctors recommend that the majority of dietary fat intake should come from monounsaturated and polyunsaturated fats. 

                  Explain why. 

                  [2 marks]

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                    Question 3a

                    Marks: 2
                    a)

                    Typical energy content values of various food group molecules are given in the table below. 

                    Food Group Typical energy content / kJg-1
                    Protein 15
                    Carbohydrate 17
                    Fat 38


                    State the molecular feature of fats that allows them to contain more energy per gram than carbohydrates or proteins.

                    [2 marks]

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                      Key Concepts
                      Long Term Storage

                      Question 3b

                      Marks: 4
                      b)

                      The diagram shows a cell with a role in storage.

                      h-3b

                      i)

                      Identify structures X, Y and Z in this diagram.

                      [3 marks]

                      ii)

                      Suggest which tissue this cell forms part of.

                      [1 mark]

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                        Key Concepts
                        Long Term Storage

                        Question 3c

                        Marks: 2
                        c)

                        A person's body mass index is 26.4 and their mass is 78.3kg.

                        Calculate the person's height in metres, to 2 decimal places. The formula for BMI is shown below:

                        h-3c-1

                        [2 marks]

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                          Question 3d

                          Marks: 4
                          d)

                          A newspaper heading states that "High fat diets lead to weight loss!" based on the following study and data. 

                          Scientists carried out a study across five years in which 8254 participants followed one of three diets:

                            • a Mediterranean diet with added extra virgin olive oil
                            • a Mediterranean diet with added nuts
                            • a low fat diet 

                          None of the diets involved reducing calories or increasing physical activity.

                          The graph below shows the results of weight loss in participants after five years.

                          weight-loss-per-cent-

                          Use the data and information provided to evaluate the newspaper's claim. 

                          [4 marks]

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                            Key Concepts
                            Lipids: Health Claims

                            Question 4a

                            Marks: 2
                            a)

                            Explain why cholesterol forms associations with proteins called lipoproteins eg. LDL (low density lipoproteins) and HDL (high density lipoproteins).

                            [2 marks]

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                              Question 4b

                              Marks: 4
                              b)

                              Outline the series of events by which low density lipoproteins (LDLs) raise the risk of a person suffering from coronary heart disease. 

                              [4 marks]

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                                Question 4c

                                Marks: 3
                                c)

                                Many claims about the health benefits and drawbacks of food are made. One such is the claim that a high consumption of trans- fats causes coronary heart disease. 

                                Evaluate this claim. 

                                [3 marks]

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                                  Key Concepts
                                  Lipids: Health Claims

                                  Question 5a

                                  Marks: 8

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

                                  a)

                                  Compare and contrast the compounds glycogen and starch. 

                                  [8 marks]

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                                    Question 5b

                                    Marks: 3
                                    b)

                                    Sketch a labelled diagram of the part of a trans-fatty acid that identifies its chemical structure as trans-.

                                    [3 marks]

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                                      Key Concepts
                                      Fatty Acids: Types

                                      Question 5c

                                      Marks: 4
                                      c)

                                      A healthy 35 year-old man of height 1.75m has a mass of 95kg. 

                                      He calculated correctly that his Body Mass Index was 31, which places him in the 'obese' category. Online sources he read gave him cause for concern about his future health prospects. 

                                      Evaluate the claim that a BMI of 31 is detrimental to his health. 

                                      [4 marks]

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