K.C.S.E Biology Q & A - MODEL 2015PP2QN01
The diagram below illustrates a blood capillary surrounding a structure for gaseous exchange in human beings.
(a) Name the gaseous exchange structure.
(b) Identify the gases labelled Y and Z.
(c) How does the gas labelled Y reach the inside of the blood capillary?
(d) How does cigarette smoking lead to lung cancer?
(b) Y - oxygen/O2;
Z - Carbon (IV) Oxide/CO2;
(c) Oxygen concentration is lower in the blood capillary than in the alveolus; oxygen diffuses; through the epithelium and endothelium of capillary wall, plasma into the red blood cells where it combines with haemoglobin.
(d) Cigarettes/tobacco contains tar; tar contains carcinogenic substances; which trigger cancer