BIOLOGY 5090 · STRUCTURED PRACTICE
1
Enzymes are essential biological catalysts present in all living organisms.
(a)
[2]Define the term biological catalyst.
(b)
[5](i)
[3]Describe how an enzyme catalyses the breakdown of a specific substrate molecule with reference to the lock-and-key hypothesis.
(ii)
[2]Explain why a high temperature above 60 °C prevents the lock-and-key mechanism from functioning.
(c)
[2]Figure 5.1 shows energy profile curves and for a metabolic reaction. Identify which curve represents the enzyme-catalysed pathway and explain how the enzyme alters the activation energy of the reaction.
Total: 9 marks