Why Correct: Pancreatic juice contains high concentrations of pancreatic amylase, which digests starch into maltose and dextrins in the small intestine.
Distractor Analysis: Brain tissue produces neurotransmitters but not digestive enzymes. Blood contains hormones and plasma proteins but minimal amylase. Thyroid gland secretes thyroxine and calcitonin hormones, not digestive enzymes.
Takeaway: Salivary glands also produce salivary amylase (ptyalin), but pancreatic amylase is more significant for complete starch digestion.

Why Correct: Gastric glands secrete pepsinogen, which hydrochloric acid converts to pepsin in the stomach, breaking proteins into peptides.
Distractor Analysis: Insulin is a pancreatic hormone regulating blood glucose. Ptyalin is salivary amylase breaking starch in the mouth. Trypsin is a pancreatic protease acting in the small intestine.
Takeaway: Gastric juice contains HCl, pepsin, and mucus; HCl activates pepsinogen to pepsin and kills microbes.

Why Correct: Ruminants are herbivorous mammals with a specialized four-chambered stomach (rumen, reticulum, omasum, abomasum) that allows them to ferment plant material through microbial digestion and regurgitate cud for re-chewing.
Distractor Analysis: Dogs are carnivores with a simple monogastric stomach adapted for digesting meat. Pigeons are birds with a two-part stomach (proventriculus and gizzard) for grinding seeds. Chameleons are reptiles with a simple stomach for digesting insects.
Takeaway: Other common ruminants include goats, sheep, deer, buffalo, and giraffes, while horses and rabbits are non-ruminant herbivores that use hindgut fermentation.

Why Correct: Salivary amylase (ptyalin), secreted by the salivary glands, begins starch digestion in the mouth—the first enzyme to mix with food in the digestive tract. It acts on cooked starch, breaking it into maltose and dextrins.
Distractor Analysis: Pepsin is secreted in the stomach by chief cells and acts on proteins in acidic pH. Cellulase is not produced by humans; it is found in ruminants and some microbes. Trypsin is a pancreatic enzyme that acts in the small intestine on proteins and peptides.
Takeaway: The sequence of digestive enzymes: mouth (salivary amylase) → stomach (pepsin) → small intestine (pancreatic amylase, trypsin, lipase). Remember that amylase appears first at pH ~7 in the mouth.

Why Correct: Salivary glands secrete ptyalin (salivary amylase), which begins the digestion of starch into maltose in the mouth.
Distractor Analysis: Erepsin (peptidase) is in the small intestine and digests peptides. Chymotrypsin and trypsin are pancreatic proteases that act in the duodenum on proteins.
Takeaway: Only ptyalin is present in saliva; all other options are secreted by the pancreas or intestinal glands.

Why Correct: Rabbits are hindgut fermenters; cellulose digestion occurs in the caecum through microbial action.
Distractor Analysis: The rectum stores feces; ileum is part of the small intestine for nutrient absorption; colon absorbs water and electrolytes. None of these sites digest cellulose.
Takeaway: Herbivores like rabbits and horses have an enlarged caecum for cellulose digestion; ruminants use the rumen.