Many animals have a heart and circulation. The table shows the time taken for a molecule to diffuse over different diffusion distances. (i) Complete the table to show the missing values. (2) (ii) Explain why it is important for body cells to be close to capillaries to meet the demands of respiration. Use the information in the question and the table to support your answer. (3)

Answer:

An explanation that makes reference to three of the following points:
- to supply the \{cells / tissues\} with \{oxygen / glucose\} (for respiration) (1)
- to remove the carbon dioxide (produced) (1)
- a small (diffusion) distance results in a faster the rate of \{diffusion / exchange\} (1)
- credit use of data (with at least one comparable unit) to support mp 3 (1)

Knowledge points:

Solution: