Question

2. (a) Describe briefly the role of the stomach in digestion. [8 marks]
(b)(i) Name three parts of plants in which food can be stored. (ii) Give one example in each case. [6 marks]
(c) Explain briefly how the level of sugar in the mammalian blood can be regulated. [6 marks]

Accepted Answer

(a) The role of the stomach in digestion is mainly as a result of the presence of the gastric juice. The gastric juice contains pepsin, rennin and HCl. Pepsin converts protein to peptones. Rennin curdles/coagulates milk — it does this by converting soluble caseinogens to insoluble casein. HCl helps to neutralize the base in the saliva and also activates pepsin (it converts inactive pepsinogen to active pepsin).

(b)(i)/(ii) Roots: cassava and sweet potatoes. Stems: sugarcane and ginger. Leaves: onions and garlic.

(c) The regulation of blood sugar is done by the liver, using the hormones (insulin and glucagon) secreted by the pancreas. When the blood sugar level is high, the pancreas stimulates the... conversion of glucose into glycogen. When the blood sugar level is low, the pancreas secretes glucagon which stimulates the conversion of glycogen back to glucose.

WAEC Biology 2012 Theory — Question 2

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