Biology Paper 3 Questions and Answers - MECS Cluster Joint Mock Examinations 2022

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QUESTIONS

  1. You are provided with solution W ,Solid Q, Iodine solution ,Benedict’s solution, Hydrochloric acid  and Water bath.
    1. Using reagents provided carry out tests to determine the food substance present in solution W
      Record the procedure ,observation and conclusion in the table below
      Food test Procedure Observation Conclusion
             
    2. Label three test tubes as A, B and C. Place 3ml of Solution W into each test tube. Divide solid Q into three equal portions.
      To the test tube A add one portion of solid Q and shake thoroughly 
      To the test tube B add the second portion of Solid Q shake thoroughly and heat to boil.
      To the test tube C add the third portion of solid Q, followed by 8 drops of 2M hydrochloric acid and shake to mix.
      Place the three set ups into a water bath maintained at 37oc for 40 minutes.
      Add equal amounts of Benedict’s solution to each of three test tubes and heat to boil. Record your observation.
      Set up A ………………………………………………………………………1mk
      B ………………………………………………………………………1mk
      C ……………………………………………………………………...1mk
      Account for your observations above (3mks)
    3. Name any other factor that affects the reaction above.   (1mk) 
    4. Give a reason why temperature of the water bath was maintained at 37oc (1mk)
  2.      
    1. You are provided with Flower specimen K. Use it to answer the questions that follow
      1
      1. Name the type of gynoecium in the flower.(1mk)
      2. With a reason state the agent of pollination.
        Agent of pollination………………………………………………………….……………1mk
        Reason ………………………………………………………………………………….. 1mk
    2. The photographs labelled Q, R,and S are sections of some plant parts.
      2
      1. Name the type of placentation in the specimens shown in photographs Q, R and S .With
        Reasons (6 marks) 
        Fruit Placentation Reason
      2. Giving a reason in each case, name the mode of dispersal of the specimen in photograph Q and S (4marks)
        Q
        Mode………………………………………………
        Reason……………………………………………
        S
        Mode………………………………..……………
        Reason……………………………………………
      3. What type of fruit is R .Give a reason.(2mks)
  3. The diagram below represents a section of human skeleton and muscles.
    3
    1.      
      1. Name the parts labelled : W, S, R, Q 1mk
      2. What is the significance of part A (1mk)
      3. Describe the role of Q during inhalation. (2mks)
      4. Name the type of muscle on the diagram above.(1mk)
      5. What type of joint is at P  (1mk)
    2. Name the bone that articulate with R at:
      1. Proximal end  (1mk)
      2. Distal end (1mk)

CONFIDENTIAL
REQUIREMENTS

  • Each candidate will require;
  • 50ml of Solution W- Starch solution, prepared with warm water.
  • Solid Q -5g of Diastase  in a stoppered container
  • 4 test tubes in a rack
  • 4 Droppers
  • 100ml plastic beaker
  • 10ml measuring cylinder
  • Test tube holder
  • Spatula
  • Three labels
  • Means of timing(Wall clock/stop watch)

Access  to

  • Benedict’s solution placed in a test tube with a dropper
  • 1M Hydrochloric acid with dropper.
  • Iodine solution with a dropper
  • Source of heat
  • Hot water bath maintained at 37ºC

NB/Question 2 and 3 Photos should be coloured



MARKING SCHEME


    1.        
      Food test Procedure Observation Conclusion
      Reducing sugar(s); 
      Reject: Specific sugars e.g. Glucose/ Simple sugars/ Monosaccharide(s) 


      To 1ml/ 2ml or drops of the solution W (in a test tube) add 1ml/ 2ml\drops of  Benedict’s solution; [food substance and Benedict’s solution used must be the Equal proportion] Heat to boil/  Accept Place in a hot water bath
      √Reject: Benedict ^/ benedict’s/  Benedict’s only
      Note: √Procedure must  be correct, all the way√ Quantities used- ratio of 1:1
      Blue colour persist



      Reducing sugars Absent


       
      Starch



      To the( drops /2ml/1ml )of solution W  in a testtube ,Add drops iodine solution
      Reject ,iodine only



      Blue black colour
      Reject any other colour,
      Accept black
      Starch present




    2. Set up
      A - Orange colour  1mk
      B  - Blue colour/ Green  1mk
      C - Blue colour/ Green  1mk
      Account for your observations  above 3mks
      Solid Q was an enzyme Hydrolysed/breakdown Starch into sugars/Glucose in A
      In testtube B Boiling denatured the enzyme hence starch was not hydrolysed.
      In testtube C Starch was not hydrolysed ,Acidic pH denatured the enzyme
    3. Substrate concentration; Inhibition ; Coenzyme and co-Factor
    4. To provide Optimum/suitable temperature for enzyme reaction.
  1.      
    1.      
      1. Syncarpous
      2. Agent of pollination……Insect  Accept correct example of an insect eg Bee1mk
        Reason   1mk
        Brightly coloured petals 
    2.      
      1. Q Marginal placentation - Placenta running longitudinally with seeds in a single line
        R Axile/ central placentation –Placenta centrally placed/ presence of loculi/chambers
        S Parietal placentation.-Ovary wall divided by placenta which is on ridges with many seeds attached 
      2. Q Mode Self - dispersal
        Reason - The pods contains lines of weakness/sutures.
        S Mode - Animal 
        Reason - Succulent /fleshy /brightly coloured. Any 1mk
      3. Berry
        Reason:
        • Has a centrally placed placenta 
        • Has many seeds 
        • Presence of loculi(with juicy sacs) 
  2.     
    1.      
      1. W - Ilium
        S - Rib
        R - Humerus
        Q - External intercoastal muscles
      2. Allow passage of nerves and blood vessels(1mk)
        Make pelvic girdle less denser/lighter to reduce the weight load supported by hind limb
      3. It Contract moving Ribcage upward and outward,This increase volume of thoracic cavity reducing pressure in the thoracic cavity.
      4. Skeletal Muscle;
      5. Ball and socket 
    2.      
      1. Scapula (1mk)
      2. Ulna (1mk)

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