Biology Paper 3 Questions and Answers with Confidentials - KCSE 2022 Mock Exams Set 2

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  • You are required to spend the first 15 minutes of the 1¾ hours allowed for this paper reading the whole paper carefully before commencing your work.
  • Answer ALL the questions in this paper in the spaces provided.
  • Candidates should answer the questions in English.


  1. You are provided with Specimen A, Solution X and Solution Y.
    1. Cut out a cylindrical portion of the petiole from Specimen A measuring 5cm long (reserve the leaves for part b of the question). Make a longitudinal section through the petiole so as to divide it into two identical straight halves as shown below;
      Place one straight half of the petiole into the boiling tube containing solution X, and label the tube as Set up I. Place the other straight half of the petiole into the boiling tube containing solution Y, and label the tube as Set up II. Leave the two set ups to stand for 30 minutes.
      Remove the two halves of the petiole from the solutions and examine them.
      1. Account for the curvature of half of the petiole in set up I. (5marks)
      2. Based on your observation of the curvature of half of the petiole in set up II, state the nature of solution Y in relation to plant cells. (1mark)
    2. Cut the leaves of specimen A into small pieces and place them into a mortar. Add 10ml of distilled water, then grind them using a pestle so as to obtain an extract called solution R. Using the reagents provided, carry out various tests using the procedures in the table below to determine the food substances in the solution R. In each case, state the observation and conclusion made. (6 marks)
       Food substance  Procedure  Observation  Conclusion
       Proteins  -Place 2ml of solution R into a test tube.
      - Add equal amount of NaOH solution.
      -Add CuSO4 solution dropwise and shake
       Reducing sugars  -Place 2ml of solution R into a test tube.
      -Add equal amount of Benedict’s solution.
      -Boil the mixture.
       Vitamin C  -Place 2ml of DCPIP into a test tube.
      -Add solution R dropwise as you shake.
    3. The photograph I below shows the internal structure of Specimen A. Study it carefully and answer the questions that follow.
      1. Identify the structures labelled A and B. (2marks)
      2. State one structural difference between cells C and D. (1mark)
      3. What is the function of the part labelled E ? (1mark)
  2. You are provided with Specimens X, Y and Z.
    1. State the type of dry, indehiscent fruit represented by specimen X. (1mark)
    2. With a reason, state the method of dispersal of specimen Y. (2marks)
      1. Method of dispersal.............................................................................................
      2. Reason.................................................................................................................
    3. Cut specimen Z transversely so as to obtain two identical halves. Draw and label the cut surface of one half. (3marks)
    4. Below is a photograph of the internal longitudinal section of Specimen X.
      1. Name the parts labelled P and S. (2marks)
      2. State the function of the part labelled T. (1mark)
      3. Identify the region that would stain blue black with iodine solution. (1mark)
    5. The magnification of the internal longitudinal section in the above photomicrograph was X30,000. Measure the distance of the dark horizontal line between V and W in millimetres. Calculate the actual width of the section between V and W in micrometres. (2marks)
  3. Below are photographs II and III of the mammalian kidney and skin respectively. 
    1. Identify the layers labelled F, J and K. (3marks)
    2. State the function of each of the parts labelled L and M. (2marks)
    3. Explain how the structure labelled N is adapted to its function. (1mark)
    4. Identify part in photograph II that contains glomeruli. (1mark)
    5. The cells in the layer labelled J can be examined using the light microscope shown below.
      1. Identify on the above photograph the structure that would be adjusted to improve on the clarity of blurred images of the cells in layer J. (1mark)
      2. State the significance of using a sharp razor or scalpel to cut through layer J to obtain the cells for examination in the above microscope. (1mark)
      3. Name the part labelled S in the above microscope. (1mark)
      4. State two functions of the light microscope during examination of the cells in layer J. (2marks)


Each candidate should have the following;

  • Transparent ruler
  • 20mls of distilled water in a boiling tube labelled solution X.
  • 20mls of saturated NaCl solution in a boiling tube labelled solution Y.
  • DCPIP solution
  • A large sized maize grain labelled specimen X
  • Scalpel
  • NaOH solution (about 5ml)
  • Bunsen burner
  • Labels (2 pieces)
  • Medium sized passion fruit labelled Specimen Z.
  • Test tube holder
  • Test tubes (3 pieces)
  • Complete leaf ( medium sized) of Sukuma wiki ( kales) labelled Specimen A.
  • Boiling tubes (2 pieces)
  • Mortar and pestle
  • Distilled water (about 15ml) in a small beaker
  • Benedict’s solution (about 5mls)
  • CuSO4 solution (about 2mls) with a dropper
  • Measuring cylinder (50ml capacity)
  • Test tube holder
  • Bean pod (any type of bean) or Crotalaria pod labelled Specimen Y.

Marking Scheme

      1. Solution X is hypotonic to/ less concentrated than cells/ cell sap of specimen A/ Petiole; hence water molecules move from solution X to the (cells of) petiole by osmosis; leading to increase in size of the cells/ petiole; The inner cortical cells lack cuticle; hence absorb more water/ absorb water faster than the outer epidermal cells; that are covered by cuticle ; The cortical tissue expands/ increases in size more than the epidermal tissue; leading to curvature of the petiole outwards;
      2. Hypertonic/ More conc. / Has more solute molecules/ Has less water molecules;
         Observation   Conclusion
       Proteins   No colour change/ (Green) colour  Of solution R persists;  Proteins absent;
       Reducing sugars   1. Colour changes to green/ Green Colour of solution R persists; 
      2. Acc. No colour change 
      Note: rj No change alone
      Response 1. are matched
      Response 2. are matched
       1. Traces/ little reducing sugar present;
      2. Reducing sugar Absent
      Vitamin C  DCPIP solution is decolourised/   Becomes colourless; Vitamin C Present;
      1. A Cuticle;
        B Upper epidermis/ Upper epidermal cell/ layer;
         Cylindrical/ regular  Irregular
         Closely packed  Loosely packed
         Contain chloroplast  Contain fewer chloroplast
        Note: Mark first one only
      3.  Allows for free diffusion/ circulation of respiratory gases/ water vapour;
    1. Caryopsis;
      1. Self dispersal/ Explosive mechanism;
      2. Presence of lines of weakness/ sutures; Rj weak lines
      1. P Coleorhiza;
        S Plumule;
      2. Protects S/ plumule from damage by soil particles;
      3. Q/ Endosperm;
    5. Distance between V and W = 3.5 – 13.7mm
      Actual width = 13.5 x 1000 ; OR Actual width = 13.7 x1000
                                   X30,000                                   X30,000
                           = 0.45micrometers;                = 0.46micrometers
      Actual width =    13.6 x 1000    ;
      = 0.45micrometers;
    1. F Cortex;
      J Cornified layer;
      K Granular layer;
    2. L Secrete sebum which keeps hair and epidermis supple/ waterproof/ contain antiseptic substances/ kill micro-organisms;
      M Conduct sweat to the skin surface;
    3. Coiled to increase surface area for absorption of excess water/ mineral salts/ urea/ lactic acid/ sweat from the surrounding blood vessels/ tissues;
      Made up of numerous secretory cells that absorb excess water / mineral salts/ urea/ lactic acid/ sweat;
    4. F/ Cortex;
      1. Q/ Fine adjustment knob;
      2. To avoid destruction/ distortion/ of the cells/ tissues/ layer;
        To obtain thin sections;
        Note: Any one
      3. Hinge/ Hinge screw;
      4. Magnifies the cell;
        Increases the resolution/ resolving power of the eye;

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