(a)[3]
Complete Table 4.1 by naming the transport mechanism shown in each example.
(b)[2]
Oxygen continually enters and leaves red blood cells. Fig. 4.1 presents an oxygen dissociation curve for adult human haemoglobin. The steepest part of the curve lies between $2.6\,\text{kPa}$ and $4.2\,\text{kPa}$. Explain the significance of this for respiring tissues.