NEET Biology Digestion and Absorption MCQs Set 13

Answer: (c) HCl

Explanation:
1. Parietal cells secrete HCl and intrinsic factor. Mucin comes from mucous cells and pepsinogen from chief cells.

Teacher's Note:
1. Remember the three gastric cell types: mucous (mucus), chief (pepsinogen), parietal (HCl and intrinsic factor).

Answer: (a) Ameloblasts

Explanation:
1. Ameloblasts of the ectoderm form enamel, the hardest substance of the body. Odontoblasts form dentine.

Teacher's Note:
1. Enamel is ectodermal while dentine and pulp are mesodermal in origin.

Answer: (a) \( \frac{2122}{2122} \)

Explanation:
1. The formula is written I C PM M. Before the third molars (wisdom teeth) erupt, an adolescent has I 2, C 1, PM 2 and M 2 in each half jaw, giving 2122/2122.

Teacher's Note:
1. The full adult formula 2123/2123 is reached only after the wisdom teeth erupt.
2. The milk teeth formula is 2102/2102.

Answer: (a) Chief cells

Explanation:
1. Chief (peptic or zymogen) cells secrete the inactive pepsinogen. HCl then converts it to active pepsin.

Teacher's Note:
1. Chief cells = zymogen cells.
2. Oxyntic cells is another name for parietal cells.

Answer: (a) Oesophagus

Explanation:
1. The oesophagus is lined by stratified squamous epithelium that resists abrasion by food. The stomach and intestine have columnar epithelium.

Teacher's Note:
1. Different linings suit different jobs: protection in the oesophagus, secretion and absorption below.

Answer: (b) Incisors

Explanation:
1. Incisors are chisel shaped and cut food. Canines tear, while premolars and molars crush and grind.

Teacher's Note:
1. Link the shape to the job: incisors cut, canines tear, premolars and molars grind.

Answer: (a) Odontoblasts

Explanation:
1. The pulp cavity contains blood vessels and nerves and is lined by odontoblasts, which secrete dentine.

Teacher's Note:
1. Odontoblasts keep forming dentine throughout life, slowly narrowing the pulp cavity.

Answer: (b) Ampulla of Vater

Explanation:
1. The hepatopancreatic duct opens into the duodenum through the ampulla of Vater, guarded by the sphincter of Oddi.

Teacher's Note:
1. This sphincter controls the flow of bile and pancreatic juice into the duodenum.

Answer: (b) Almost neutral

Explanation:
1. Salivary amylase works at about pH 6.8 and is inactivated in the acidic stomach.

Teacher's Note:
1. Mixed saliva has a pH of 6.8, so ptyalin acts in a nearly neutral medium.

Answer: (b) Cells of acini and islets of Langerhans

Explanation:
1. Acinar cells form the exocrine pancreatic juice, while the islets of Langerhans secrete insulin and glucagon.

Teacher's Note:
1. The pancreas is a mixed gland: exocrine acini and endocrine islets.

Answer: (c) Duodenum

Explanation:
1. The duodenum is the C-shaped first part of the small intestine, and the head of the pancreas lies in its curve.

Teacher's Note:
1. Remember duodenum: about 25 cm, C-shaped, receives bile and pancreatic juice.

Answer: (c) HCl

Explanation:
1. HCl gives gastric juice a pH of about 1.8 and kills most microbes in food.

Teacher's Note:
1. HCl also activates pepsinogen and provides the acidic medium for pepsin.

Answer: (c) Glucose

Explanation:
1. Saliva contains electrolytes, bicarbonate, salivary amylase, lysozyme and antibodies, but no glucose.

Teacher's Note:
1. Lysozyme in saliva and tears is a non-specific defence against bacteria.

Answer: (c) It is important only for normal digestion of sugar

Explanation:
1. Bile salts emulsify fats and activate lipases. Bile has no role in sugar digestion.

Teacher's Note:
1. Bile contains no digestive enzymes, only salts and pigments.

Answer: (b) Succus entericus

Explanation:
1. The intestinal glands, called crypts of Lieberkuhn, secrete succus entericus (intestinal juice).

Teacher's Note:
1. Brunner's glands in the duodenum secrete alkaline mucus.

Answer: (b) Below the ears

Explanation:
1. Parotids are the largest salivary glands, lying near the ears, one on each side of the face.

Teacher's Note:
1. Remember the three pairs: parotid, sub-maxillary and sublingual.

Answer: (a) Liver

Explanation:
1. Sinusoids are wide, leaky capillaries lining the hepatic lobules.

Teacher's Note:
1. Kupffer cells in these sinusoids engulf bacteria and old cells.

Answer: (b) Kupffer's cells

Explanation:
1. Kupffer cells are macrophages in the walls of the hepatic sinusoids.

Teacher's Note:
1. Kupffer cells form part of the reticuloendothelial system.

Answer: (c) Protein

Explanation:
1. Casein is the main milk protein, which rennin converts to calcium paracaseinate in infants.

Teacher's Note:
1. Whey proteins and casein together form milk protein.

Answer: (a) Starch

Explanation:
1. Amylases hydrolyse starch and glycogen into maltose.

Teacher's Note:
1. Salivary amylase and pancreatic amylase (amylopsin) act on starch.

Answer: (d) Bile, which has no enzyme

Explanation:
1. Hepatocytes secrete bile. It contains salts and pigments but no digestive enzymes.

Teacher's Note:
1. Amylopsin, trypsin and lipase are pancreatic enzymes.

Answer: (b) Rennin

Explanation:
1. Rennin (chymosin) of infant gastric juice converts casein into paracasein, which forms a curd with calcium.

Teacher's Note:
1. Curdling slows the passage of milk so that pepsin can digest it.

Answer: (b) Sucrose into glucose and fructose

Explanation:
1. Invertase (sucrase) splits the disaccharide sucrose into glucose and fructose.

Teacher's Note:
1. Maltase gives 2 glucose, lactase gives glucose and galactose.

Answer: (a) Blood capillaries of villi

Explanation:
1. Amino acids and glucose enter the blood capillaries of the villi, while fats enter the lacteals.

Teacher's Note:
1. Water-soluble products go to blood; fat-soluble products go to lymph.

Answer: (a) Amylopsin

Explanation:
1. Amylopsin is the pancreatic amylase. Lipase acts on fat and erepsin and pepsin on proteins.

Teacher's Note:
1. Name the enzyme by the substrate: amylase starch, lipase fat, protease protein.