Biology Paper 2, WASSCE (PC), 2016

Question 2

  1. (i) Define enzymes. [2 marks]
    (ii) State five characteristics of enzymes. [5 marks]
  2. Describe briefly the role of the pancreatic juice in the digestion of carbohydrates and proteins in mammals. [4 marks]
  3. (c) A student fractured a leg, the leg was put in a cast and the student was advised to drink plenty of milk and spend some time under the sun. Explain briefly the reason for the instructions. [4 marks]
  4. (d) State five ways in which photosynthesis is of importance to humans. [5 marks]


This question was one of the popular questions answered by candidates and was fairly answered by the candidates that attempted it. While some candidates scored fairly good arks, others did not. Some candidates were able to define the term Enzymes very well although some could not express themselves very clearly but some stated the functions of enzymes instead of the characteristics requested. Many candidates had the idea of the answers to 2(c) but could not express themselves in clear words and terms. Some candidates could not answer question 2(d) properly.


The expected answer are:

(a) (i) Enzymes

- Enzymes are organic catalysts/substances;

- they are made up of proteins/protein in nature;

- that speed up/regulate the rate of biochemical reactions in cells.

(ii) Characteristics of enzymes

- are protein in nature;

- remain chemically unchanged at the end of a reaction;

- are specific in action/one or a group of enzymes will act on specific substrates;

- enzymes are required in small quantities;

- act over a specific range of temperature/optimum temperature;

- they are denatured/destroyed at high temperature/inactivated at very cold temperatures;

- act best at specific pH (either acidic/alkaline);

- most actions are reversible;

- enzyme action is retarded by poison or inhibitors;

- some are inactive and require a coenzyme/agents to activate them;

- enzymes are soluble;

- can function outside the body of the organism that produces them;

- speed up rate of biochemical reactions in cells


(b) Role of pancreatic juice in carbohydrate and protein digestion

- pancreatic juice provides alkaline medium for the action of the enzymes involved;

- which operates in the small intestine/duodenum;

- pancreatic juice contains amylase/amylopsin;

- which converts starch/carbohydrate to maltose sugar;

- it also contains trypsin;

- which converts proteins to peptone/polypeptide/peptide.


(c) Reason for the instruction

- Milk is a source of calcium/phosphorus;

- Milk is also a source of vitamins (A, B6, B12, C, D, E, K) necessary for growth and repair;

- Milk is also a source of casein (protein) for growth and repair;

- Milk is also a source of lactose (milk sugar for energy);

- which is needed for bone ossification/formational healing;

- sunlight is needed for the formation of vitamin D in the skin;

- vitamin D is required for the absorption of calcium and phospholipids;

- which is needed for the hardening of bones.


(d) Importance of photosynthesis to humans

- Food produced by photosynthesis is consumed by all humans;

- oxygen produced during photosynthesis is taken in by man;

- photosynthesis reduces carbon dioxide from the atmosphere which would have become a pollutant/brings about purification of air;

- provides raw materials for industries e.g. (wood, sugar, pharmaceuticals/medicinal herbs);

- provides humans with fossil fuel.