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CAIE A-Level Biology 3.1.2 Enzyme Mode of Action

Practise explaining complementary binding, induced fit, enzyme–substrate complex formation, reduced activation energy and product release with the enzyme unchanged.

Syllabus
2028–2030
Course
Biology 9700
Level
AS

Exam points

  • describe complementary substrate binding and temporary enzyme–substrate complex formation
  • explain induced fit as an active-site shape change that improves catalytic interactions
  • state that enzymes lower activation energy and are released unchanged after product formation

3.1.2—Enzyme mode of action question 1

[Maximum number: 3]

Prostaglandins are small lipids produced in many tissues of the body. One role of prostaglandins is to cause inflammation at the site of an injury or infection. Inflammation is the normal first response of the immune system to injury or infection.

Cyclooxygenase (COX) is an enzyme that catalyses one of the steps in the reaction pathway for the formation of prostaglandins from phospholipids. The reaction pathway occurs in the smooth endoplasmic reticulum (SER) of cells. Part of the reaction pathway is shown in Fig. 1.3.

Fig. 1.3

Fig. 1.3

Sometimes inflammation can have side-effects, such as pain. Aspirin is a drug that can be used to reduce these side-effects.

Aspirin reduces the catalytic activity of the COX enzyme by modifying the R-group of one of the amino acids.

Suggest how modifying the R-group of an amino acid in the COX enzyme can reduce the catalytic activity of the enzyme.

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