Which one of the following pairs of food components in humans reaches the stomach totally undigested?
(a) Protein and starch
(b) Starch and fat
(c) Fat and cellulose
(d) Starch and cellulose
(c) In humans, starch is digested in buccopharyngeal cavity. Cellulose is not digested in the humans because cellulose contains β-1,4-linkage and vertebrates themselves do not possess any enzyme capable of hydrolysing B-1,4-linkages. Protein is digested in stomach and fat in small intestine. Thus, in the given options, fat and cellulose reach totally undigested in the stomach of humans.