Moist sugar-beet pulp is decomposed by microorganisms in an aerated, insulated treatment vessel. Although the vessel has no heater, the pulp reaches 32 ∘C32\,^{\circ}\text{C}32∘C, which is below the optimum temperature of the decomposer enzymes. The pulp is then spread into shallow, uninsulated trays. Its moisture content and oxygen supply are kept the same.
Which explanation is correct?
Spreading the pulp reduces its surface area, so decomposer enzymes contact less material and decomposition decreases.
Keeping the pulp moist fills its air spaces, so aerobic respiration and decomposition decrease.
More heat from microbial respiration is transferred to the surroundings, so enzyme activity and decomposition decrease.
Less heat from microbial respiration is transferred to the surroundings, so enzyme activity and decomposition increase.
101 exam-style questions on Edexcel GCSE Biology 9.3 Material cycles and decomposition, covering 9.3.1 Cycling of materials through ecosystems, 9.3.2 The carbon cycle, 9.3.3 The water cycle, 9.3.4 The nitrogen cycle, 9.3.5 Indicator species and pollution, 9.3.6 Decomposition in preservation and composting, and 9.3.7 Rate changes in decay of biological material. Each one has a worked solution and a mark scheme showing where the marks go.