Quick questions on Biological reactions and enzymes - WJEC A-Level Biology

A useful rule is that the rate roughly doubles for each $10\,^\circ\text{C}$ rise up to the optimum (the temperature coefficient $Q_{10} \approx 2$). Beyond the optimum (around $40\,^\circ\text{C}$ for many human enzymes) the increasing vibration of atoms breaks the weak bonds holding the tertiary structure, the active site loses its complementary shape, and the enzyme is denatured permanently.

Most human enzymes have an optimum near pH 7, but pepsin in the stomach works best near pH 2. Moving away from the optimum changes the charge on amino acid side chains, breaking ionic bonds and hydrogen bonds in the active site.

At low substrate concentration the rate is limited by how often substrate meets an active site, so adding substrate increases the rate. Once every active site is constantly occupied the enzyme is saturated and the rate plateaus. Raising enzyme concentration raises the plateau, provided substrate is not limiting.

State what is meant by the active site of an enzyme. [1 mark]

Explain why adding more substrate reverses the effect of a competitive inhibitor but not a non-competitive inhibitor. [2 marks]

A reaction reaches an initial rate of $1.8$ cm cubed per second. Suggest two changes to the conditions that would increase this initial rate, and explain each. [4 marks]