Friday, October 16, 2009

[Biology SPM] Exam Pointers I

Source: Maths & Science Guide

  1. State the effect of an enzyme on an oil molecule.

  2. State two conditions that denatures an enzyme.

  3. State the conditions of the valves during atrial systole.

Frequent Mistakes

Student's answer
  1. It converts it to fatty acid and glycerol.

  2. Temperature and pH.

  3. The valves close and the wall of the atria contract.
Tutor's comments:
  1. The word "convert" does not convey the information that it is done with water being the reagent, and that it is a breakdown process. The correct terminology should have been "hydrolyses".

  2. The student stated temperature and pH but did not give an indication on whether both conditions should be high or low.

  3. The keyword here is "the conditions of the valves". Students should know that there are two types of valves - atrio-ventricular valves (bicuspid and tricuspid valves), and semilunar bases at the aorta and pulmonary artery.

Correct Answers
  1. It hydrolyses it to fatty acids and glycerol.

  2. Extreme temperature and extreme pH.

  3. a) The semilunar valves close.
    b) The bicuspid and tricuspid valves open.


  1. 1. Can hydrolyses be substituted with digests/breaks down ?

  2. Our diet consists of proteins, carbohydrates and fats that have to be digested and absorbed by the intestines in order to nourish the body. While some of these substances are macromolecules, most of them have complex structures that cannot be directly absorbed by intestinal cells. The digestive process consists of breaking down these food materials into smaller molecules that can be absorbed.

    Hydrolysis, the process by which chemical bonds are broken by the addition of a molecule of water, is the basic chemical reaction by which these molecules are split into their constituent, smaller molecules. Interestingly, although proteins, carbohydrates and fats are vastly different in their structures and make up, it is the same chemical reaction, hydrolysis, that is required for their break down during the chemical digestion process.


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