Page 70 - Biology_F5

Cytology

Enzymes are complex, three dimensional
globular proteins that are produced in the
cells of organisms. They are biological
catalysts, since they alter the rate of
different physiological processes in living
organisms. They are also found in natural
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secretions, such as plant juices, milk and
(a) (b) (c) (d) the digestive juices where they catalyse
Figure 1.41: Test tubes with sample several metabolic reactions or processes
solutions in different concentration taking place in the living cells. A compound
with which the enzyme combines is called
(a) Based on the observations, which test a substrate. The substrate fixes itself in an
tube had a food item with maximum
protein content? active site of the enzyme whose shape is
ideal for accommodating it. The active
(b) Classify the proteins based on their site is a group of amino acids comprising
structure and function the region of the enzyme into which

1.4.4 Enzymes the substrate fits in order to catalyse the
reaction. By acting as catalysts, enzymes
Task 1.7 lower the activation energy. Activation
Search from internet sources the energy is the minimum amount of energy
simulations for activation energy in that is required to activate a substrate
enzymic reaction. Note down the molecule to a condition in which it can
activation energy of the reactants with undergo biological transformation (Figure
an enzyme and without enzyme. 1.42).

Activation energy (EA)
without enzymes

Activation energy (EA)
with enzymes
Free energy (G) Energy of Change in

reactants
free energy
(AG)

Energy of products
Progress of reaction

Figure 1.42: Activation energy for an enzyme-catalysed reaction and an un-catalysed reaction

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