Biology Paper 2, Nov/Dec 2015

Question 2


  1. Write a balanced chemical equation for the process of photosynthesis.      [4 marks]
  2. Make a drawing 8cm – 10cm long of the transverse section of a dicotyledonous leaf and label fully.   [11 marks]
  1. State five functions of a mammalian liver.  [5 marks]

Observation

Candidates could not write a well balanced chemical equation for photosynthesis and majority
could not also draw T.S of a dicotyledonous leaf but drew a dicotyledonous leaf. The few candidates that tried to draw wrongly labelled the parts or did not label the parts properly with spelling errors.
For question 2 (c), majority could not give up to three functions of the liver out of the five required.

 

The expected answer are:
(a) Chemical equation of photosynthesis                                   
6C02+6H2O    Chlorophyll    C6H12O6+6O2
Sunlight                                 

correct reactant (CR)                 x 1
correct product (CP)                  x 1
correct condition (CC)                 x 1
balancing       (BL)                x 1

[4 marks]

 

(b)  Diagram of the transverse section of a dicotyledonous leaf

 

Title (T)                                        x1
Quality (Q)
Size (Sz) (8 – 10cm)                               x1
Clarity of lines (CL)                               x1
Neatness of labels (NL)                            x1

 

Details (D)
Upper epidermis with cuticle layer shown (EC)               x 1
Spongy mesophyll with irregular cells     (SI)             x 1
Palisade mesophyll longitudinally packed cells (PP) x 1                  

Labels (L)
Cuticle; upper epidermis/epidermal cell; palisade mesophyll; spongy mesophyll; vein/vascular bundle/tissue; xylem vessel; phloem vessel; intercellular airspace; stoma; guard cell; chloroplast; lower epidermis/epidermal cell.


(c)       Functions of the mammalian liver

  • carbohydrate/protein/fat metabolism; - deamination of excess amino acids;
  • production of bile;  - manufacture of foetal red blood cells;
  • protein synthesis;   - manufactures fibrinogen for blood clotting;
  • iron storage/potassium/copper/minerals; - heat production;
  • detoxification;  - storage of vitamins B12, A, D;
  • conversion of blood glucose to glycogen
  • and vice versa/regulation of blood sugar; - removal of cholesterol  from the blood;
  • blood storage;  - elimination of sex hormones after functioning;
  • elimination of haemoglobin from used RBC; - Any other correctly named functions.