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. Y Z (c) How does the gas labelled Y reach the inside of the blood capillary? (d) How does cigarette smoking lead to lung cancer?
ANSWERS
​.(a) Alveolus;
(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 |
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