1.(a) (i) What are enzymes? [ 2 marks]
(ii) State five characteristics of enzymes[ 5 marks]
(iii) Name two enzymes involved in carbohydrate digestion in the body [ 2 marks]
(b) Name the end-product of digestion of
(i) carbohydrates;
(ii) proteins;
(iii) fats. [3 marks]
(c)State two uses each of the following classes of food:
(i) proteins;
(ii) vitamins.[ 4 marks]
(d)State two ways each in which the following substances are important
in the diet of humans:
(i)Roughage;
(ii)Water. [ 4 marks]

This question was attempted by many candidates and their performance was good. In part (a)(i) candidates were able to define enzyme correctly, however, in part (a)(ii) candidates stated characteristics of enzymes, in part (a)(iii) candidates named enzymes involved in carbohydrate digestion in the body. In part (c) candidates stated uses of proteins and vitamins. In part (d) candidates stated ways in which roughage and water are important in the diet of humans.
The-expected answers were as follows:
l(a)(i) Enzymes
Enzymes are biological/organic catalysts protein in nature, produced in minute quantities in living cells.
(ii) Characteristics of enzymes
they are made up of protein/protein in nature
over heating/excessive heating destroys enzymes
they work best within a certain specific range of temperature
they work best within a certain range of PH
they are specific in action/particular reaction/act on specific substrate
they remain unchanged at the end of the reaction
they are activated by co-enzymes/co-factors
they increase the rate of chemical reactions
they are required in small amounts.
(iii) Enzymes involved in carbohydrate digestion
salivary amylase/ptyalin
maltase
sucrose
pancreatic amylase
lactase
(b) End product of digestion of classes of food
(i) Carbohydrates
glucose/simple sugar/fructose/galactose
(ii)Proteins
amino acids e.g. peptones and peptides
(iii)Fats
fatty acid/glycerol.
(c) Uses of the following classes of food
(i)Proteins
formation of enzymes, hormones, antibodies and hairs
growth/formation of new cells.
repair of body tissues
release of energy.
(ii)Vitamins
required in the absorption of calcium or phosphorus
important in the formation of bones
prevents rickets/Aids healthy growth
prevents deficiency diseases/named diseases.
(d) Importance of the following substances in the diet human
(i) roughage
aids digestion and adds to the food bulk
it helps the food to pass through the digestive system easily/easy movement of the
bowel/prevent constipation
it reduces the risk of bowel cancer
(ii) Water
serves as a solvent for digestion
softens the food
medium for enzyme/chemical activity
transport of digested food
forms 70% of body fluid