Answer to Q 3

The structure of red blood cells relates to their function of carrying respiratory gases.

(i)         Name the gases that are carried by red blood cells

carbon dioxide & oxygen / CO₂ & O₂                                                                                                                [ 1 ]

(ii)        State TWO characteristics if red blood cells that are related to their function

2 of:

large surface area / large sa / concave shape gives large surface area or sa; no nucleus to give more space / volume for [containing] haemoglobin; thin membrane for rapid diffusion [of gases]; do not allow ‘many red blood cells' or similar

[ 2 ]

(iii)       Carbon monoxide poisoning can occur from the inhalation of fumes from faulty gas boilers and vehicle exhausts.  Persons affected by carbon monoxide poisoning typically present a bright red skin colour.  Explain this statement.

haemoglobin has greater affinity for CO / carbon monoxide than O₂ / oxygen; CO / carbon monoxide attaches to haemoglobin more readily than oxygen / O₂; bright red colour due to CO loading of iron / bright red colour characteristic of carbon monoxide loading / poisoning [ 2 ]

[ Total: 5 ]