Competitive Exams: Enzymes

Enzymes are biological catalysts. A catalyst enhances the speed of a chemical reaction. Thus, enzymes are catalysts, which enhance the speed of the chemical reactions taking place in the body.

Properties of Enzymes

Enzymes are proteins, therefore, they become denatured by heat, which means that when heated above 40oC, they change shape and do not work anymore. When the temperature is lower than normal, enzymes become inactive. Enzymes are specific, which means that every enzyme catalysis only one type of food substance, for example, the enzyme amylase catalysis only starch, and does not take part in any other chemical reaction involving another food substance.

Enzymes do not take part in the proper chemical reactions (they do not react), they just enhance the speed, and this property makes them used over and over again.

An enzyme catalysis a reaction involving a substrate; the particular nutrient the enzyme acts on. When the reaction is complete, a product is produced. An example is amylase acting on starch. Amylase, which is an enzyme, acts on its substrate

(starch), to produce a product (maltose), which is a simpler type of carbohydrate. The rate of productivity by enzymes is very affected by temperature and by pH. The graph shows the rate of the activity by the enzymes in relation to temperature. The rate increases slowly when the temperature rises between 10oC to 40oC, but when the temperature rises further, activity decrease drastically, because enzymes are being denatured.

The graph here below shows the sensitivity of enzymes to pH. It is a bell-shaped graph, showing that the enzymes work best that at their optimum pH, which in this case is pH 2.

An example: The Lock and Key Theory: The lock and key theory is how scientists believe enzymes catalyze their substrate. It is shown in this diagram. The substrate approaches the enzyme, then the substrate docks into the active site, where the reaction takes place. After the reaction, the enzyme releases the products.

Economic Important of Enzymes

Enzymes can be artificially made and used in Biological washing powders. These washing powders contain enzymes that work at a suitable temperature (e. g. 40oC) and dissolve food stains from fabrics. They are specific to particular stains. Protease is used for tenderising meat and removing hair from hides. Amylase is used to covert starch to sugars to make syrups and juices.

Enzyme Inhibitors There are some poisons, such as cyanide and arsenic that block the enzymes ‘active site, therefore the substrate cannot enter the active site and the reaction doesn't take place. Certain pesticides block the active site of pests’ enzymes so that its respiratory system stops working and the pest dies.

Dentition: The teeth are made of hardest substance found in the body. Humans have 4 types of


Incisors: Adapted for cutting food.

Canines: For holing and tearing.

Premolars: For chewing and grinding food.

Molars: For chewing and grinding food.

Humans aged 6 months begin to grow 20 milk teeth (baby) teeth. Once he or she is an adult, 32 permanent teeth will be developed.

The tooth is made up of 2 sections, an exposed Crown and the Root which is embedded in the gum. The enamel (calcium phosphate: CaPO3) is the upper part of the crown. It is very hard. Then beneath it there is the dentin. The tooth is primary made of dentin, which is a substance, similar to bone but harder. The central region of the tooth is the pulp cavity. It contains the pulp, which is composed of connective tissue with blood vessels, nerves etc. The pulp is connected to the blood capillaries, which give nutrients and oxygen to the dental cells.

Tooth decay (dental caries) is caused by bacteria in the mouth which produce acids to digest food stuck in and between the teeth.

To prevent tooth decay, varies activities must be regularly done:

  • Brushing teeth with a fluoride toothpaste
  • Regular visits to the dentist
  • X-rays of the jaw to ensure that no cavity is being developed where the dentist cannot see
  • Use tooth floss
  • Wash mouth with a suitable mouth wash

Herbivores have different a dental system since they eat only vegetable matter. In herbivores, there is a gap called diastema between the incisors and the molars. Instead of the upper incisors, herbivores have a hard pad to pull leaves and grass out of the branches or soil. They have no canines and molars have a flat surface. Their teeth have an open root, which means that they grow continuously. Carnivores molars have cusps, to ensure that food is better chewed. They have canines, and upper incisors, while teeth have a closed root unlike herbivores.