A small photosynthesising organism takes in carbon dioxide by diffusion across its permeable outer surface. Damage reduces the area exposed to the surroundings from 48 cm2 to 20 cm2.
For this exchange surface, the diffusion rate is directly proportional to the exposed area. The concentration difference and surface thickness do not change.
How does the damage affect the rate of carbon dioxide diffusion into the organism?
It becomes (48−20)÷20(48-20)\div20(48−20)÷20 of the rate before the damage.
It becomes (48−20)÷48(48-20)\div48(48−20)÷48 of the rate before the damage.
It becomes 48÷2048\div2048÷20 of the rate before the damage.
It becomes 20÷4820\div4820÷48 of the rate before the damage.
102 exam-style questions on Edexcel GCSE Biology 8.1 Exchange surfaces and diffusion, covering 8.1.1 Introduction to exchange and transport, 8.1.2 Alveoli adapted for gas exchange, 8.1.3 Factors affecting rate of diffusion, and 8.1.4 Rate of diffusion using Fick's law. Each one has a worked solution and a mark scheme showing where the marks go.