Question
Succus entericus is referred to as [NEET 2021]
(a) pancreatic juice
(b) intestinal juice
(c) gastric juice
(d) chyme
Answer/Explanation
Ans. (b)
Succus entericus also known as intestinal juice. It is a fluid secreted in small intestine in small quantity. The secretion of the brush border cells of the mucosa along with the secretions of goblet cells constitute succus entericus. It consist of various enzymes like lipases, disaccharides, nucleosidases etc. and mucus.
Question
Intrinsic factor that helps in the absorption of vitamin- $\mathrm{B}_{12}$ is secreted by [NEET (Oct.) 2020]
(a) goblet cells
(b) hepatic cells
(c) oxyntic cells
(d) chief cells
Answer/Explanation
Ans. (c)
Parietal cells or oxyntic cells secrete $\mathrm{HCl}$ and intrinsic factor. These intrinsic factors are essential for absorption of vitamin- $\mathrm{B}_{12}$. Goblet cells secrete mucus. Peptic or chief-cells secrete the proenzyme pepsinogen. Hepatic cells secrete bile.
Question
The proteolytic enzyme renin is found in [NEET (Oct.) 2020]
(a) intestinal juice
(b) bile juice
(c) gastric juice
(d) pancreatic juice
Answer/Explanation
Ans. (c)
The proteolytic enzyme rennin is found in gastric juice of infants which helps in the digestion of milk proteins, casein into paracasein.
Question
The enzyme enterokinase helps in conversion of [NEET (Sep.) 2020]
(a) trypsinogen into trypsin
(b) caseinogen into casein
(c) pepsinogen into pepsin
(d) protein into polypeptides
Answer/Explanation
Ans. (a)
The correct option is (a) because the enzyme enterokinase helps in conversion of trypsinogen into trypsin. Trypsinogen is activated by an enzyme, enterokinase, secreted by the intestinal mucosa into active trypsin. Trypsinogen is a zymogen released from pancreas.
Question
26 Match the items given in Column I with those in Column II and choose the correct option. [NEET (Odisha) 2019]
1 2 3 4
(a) (iii) (iv) (ii) (i)
(b) (iv) (iii) (i) (ii)
(c) (iv) (iii) (ii) (i)
(d) (iii) (iv) (i) (ii)
Answer/Explanation
Ans. (d)
The correct matches are
1. Rennin is a proteolytic enzyme that causes coagulation of milk.
2. Enterokinase converts trypsinogen into its active form trypsin.
3. Oxyntic cells (also called parietal cells) during digestion release stomach acid to allow release of vitamin- $B_{12}$ from food.
4. Fructose is absorbed by facilitated transport into the blood capillaries.
Question
Identify the cells whose secretion protects the lining of gastrointestinal tract from various enzymes. [NEET (National) 2019]
(a) Goblet cells
(b) 0xyntic cells
(c) Duodenal cells
(d)Chief cells
Answer/Explanation
Ans. (a)
Secretions of goblet cells protect the lining of gastrointestinal tract from various enzymes. These cells secrete mucus which along with bicarbonate ions helps in the lubrication and protection of the mucosal epithelium from the excoriation by the highly concentrated $\mathrm{HCl}$. On the other hand, axyntic or parietal cells secrete hydrochloric acid. Chief cells or peptic cells secrete proenzymes-pepsinogen and prorenin.
Question
Which of the following options best represents enzyme composition of pancreatic juice? [NEET 2017]
(a) Amylase, peptidase, trypsinogen, rennin
(b) Amylase, pepsin, trypsinogen, maltase
(c) Peptidase, amylase, pepsin, rennin
(d) Lipase, amylase, trypsinogen, procarboxypeptidase
Answer/Explanation
Ans. (d)
Pancreas consist of exocrine and endocrine part. Exocrine part secrets alkaline pancreatic juice. This juice contains trypsinogen,chymotrypsinogen, procarboxypeptidase, lipase, amylase, elastase.Concept Enhancer Renin and pepsin enzymes are present in gastric juice. Maltase is present in the intestinal juice.
Question
In the stomach, gastric acid is secreted by the [NEET 2016, Phase I]
(a) parietal cells
(b) peptic cells
(c) acidic cells
(d) gastrin secreting cells
Answer/Explanation
Ans. (a)
In stomach, gastric acid (HCl) is secreted by parietal cells of gastric gland. It makes the medium of food in stomach acidic for stimulation of proteolytic enzymes of stomach.
Question
Which hormones do stimulate the production of pancreatic juice and bicarbonate? [NEET 2016, Phase II]
(a) Angiotensin and epinephrine
(b) Gastrin and insulin
(c) Cholecystokinin and secretin
(d) Insulin and glucagon
Answer/Explanation
Ans. (c)
Cholecystokinin (CCK) and secretin are the peptide hormones that stimulate the production of pancreatic juice and bicarbonates within the alimentary canal. Secretin acts on the exocrine pancreas and stimulates the secretion of water and bicarbonate ions. CCK acts on both pancreas and gall bladder and stimulates the secretion of pancreatic enzymes and bile juice respectively. Hence, option (c) is correct.
Question
The enzyme that is not present in succus entericus is [CBSE AIPMT 2015]
(a) maltase
(b) nucleases
(c) nucleosidase
(d) lipase
Answer/Explanation
Ans. (b)
Succus entericus or intestinal digestive juice contains a variety of enzymes like disaccharidases (e.g. maltase), dipeptidases, lipases, nucleosidases. Nucleases are enzymes present in pancreatic juice that break nucleic acids into nucleotides.
Question
The initial step in the digestion of milk in humans is carried out by? [CBSE AIPMT 2014, 11]
(a) Lipase
(b) Trypsin
(c) Rennin
(d) Pepsin
Answer/Explanation
Ans. (d)
In humans, the milk protein digesting enzyme in stomach is pepsin. In calves it is rennin. It is also present in small amounts in human infants but not adults. Pepsin acts on water soluble ‘caseinogen (milk protein) to form soluble ‘casein’. This combines with calcium salts to form insoluble calcium paracaseinate, which gets readily digested enzymatically.
Question
Fructose is absorbed into the blood through mucosa cells of intestine by the process called [CBSE AIPMT 2014]
(a) active transport
(b) facilitated transport
(c) simple diffusion
(d) co-transport mechanism
Answer/Explanation
Ans. (b)
Fructose is absorbed into the blood through mucosa cells of intestine by the process called facilitated transport thus, facilitated transport is the process of spontaneous passive transport of the molecules or ions across a biological membrane via specific transmembrane integral protein.
Question
Select the correct match of the digested products in humans given in column I with their absorption site and mechanism in column II. [NEET 2013]
Answer/Explanation
Ans. (a)
Amino acids, monosaccharides like glucose, electrolytes like $\mathrm{Na}^{+}$are absorbed into the blood by active transport. Fructose and some amino acids are absorbed with the help of the carrier ions like $\mathrm{Na}^{+}$by facilitated transport. Fatty acid and glycerol cannot be absorbed into the blood. They are first incorporated into small droplets called micelles, which move into the intestinal mucosa.
Question
If for some reason our goblet cells are non-functional, this will adversely affect [CBSE AIPMT 2010]
(a) production of somatostatin
(b) secretion of sebum from the sebaceous glands
(c) maturation of sperms
(d) smooth movement of food down the intestine
Answer/Explanation
Ans. (d)
Goblet cells are something like a wineglass that present in the columnar epithelium of the mammalian intestine and secrete mucin, a mucoprotein that forms mucus when in solution. If Goblet cells become non-functional, this will adversely affect smooth movement of food down the intestine due to the absence of mucin.
Question
Carrier ions like $\mathrm{Na}^{+}$facilitate the absorption of substance like [CBSE AIPMT 2010]
(a) amino acids and glucose
(b) glucose and fatty acids
(c) fatty acids and glycerol
(d) fructose and some amino acids
Answer/Explanation
Ans. (d)
Active transport occurs with the help of energy, usually against concentration gradient. For this, cell membrane possesses carriers and gated channels. Active transport of one substance is often accompanied by permeation of other substances.
The phenomenon is called secondary active transport. It is of two main types, i.e. Co-transport, (e.g. glucose and some amino acids along with inward pushing of excess $\mathrm{Na}^{+}$) and counter transport ( $\mathrm{Ca}^{2+}$ and $\mathrm{H}^{+}$movement outwardly as excess $\mathrm{Na}^{+}$passe inwardly).
Question
A young infant may be feeding entirely on mother’s milk, which is white in colour but the stools, which the infant passes out is quite yellowish. What is this yellow colour due to? [CBSE AIPMT 2009]
(a) Intestinal juice
(b) Bile pigments passed through bile juice
(c) Undigested milk protein casein
(d) Pancreatic juice poured into duodenum
Answer/Explanation
Ans. (b)
The stools, which the infant passes out is quite yellowish due to the bile pigments. These bile pigments are released in the bile juice.
Question
Which one of the following pairs of food components in humans reaches the stomach totally undigested? [CBSE AIPMT 2009]
(a) Protein and starch
(b) Starch and fat
(c) Fat and cellulose
(d)Starch and cellulose
Answer/Explanation
Ans. (c)
In humans, starch is digested in buccopharyngeal cavity. Cellulose is not digested in the humans because cellulose contains $\beta-1,4$-linkage and vertebrates themselves do not possess any enzyme capable of hydrolysing $\beta-1$, 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.
Question
Which one of the following statement is true regarding digestion and absorption of food in humans? [CBSE AIPMT 2009]
(a) Oxyntic cells in our stomach secrete the proenzyme pepsinogen
(b) Fructose and amino acids are absorbed through intestinal mucosa with the help of carrier ions like $\mathrm{Na}^*$
(c) Chylomicrons are small lipoprotein particles that are transported from intestine into blood capillaries
(d) About $60 \%$ of starch is hydrolysed by salivary amylase in our mouth
Answer/Explanation
Ans. (c)
Chylomicrons are lipoprotein particles synthesised by intestinal epithelial cells and consisting mainly of triglycerides. Chylomicrons are the form, in which dietary fat is transported in the circulatory system.
Question
Which one of the following is the correct matching of the site of action on the given substrate, the enzyme acting upon it and the end product? [CBSE AIPMT 2008]
(a) Duodenum: Triglycerides trypsin monoglycerides
(b) Small intestine: Starch $\alpha$-amylase disaccharide (maltose)
(c) Small intestine: Proteins pepsin amino acids
(d) Stomach: Fats, Lipase micelles
Answer/Explanation
Ans. (b)
In small intestine food meats with the pancreatic juice containing $\alpha$-amylase, which converts starch into maltose, isomaltose and $\alpha$-dextrins in small intestine.
Starch $\stackrel{\text { Pancreatic } a \text {-amylase }}{\longrightarrow}$ Maltose (disaccharide)
The pancreatic juice also contains proenzymes trypsinogen, chymotrypsinogen and procarboxypeptidase. The trypsinogen is converted to active trypsin in intestine by enterokinase of intestinal juice. The trypsin converts proteins into large peptides and the large peptides are converted to dipeptide and amino acids by carboxypeptidase.
Question
What will happen if the secretion of parietal cells of gastric glands is blocked with an inhibitor? [CBSE AIPMT 2008]
(a) Gastric juice will be deficient in chymosin
(b) Gastric juice will be deficient in pepsinogen
(c) In the absence of $\mathrm{HCl}$ secretion, inactive pepsinogen is not converted into the active enzyme pepsin
(d) Enterokinase will not be released from the duodenal mucosa and so trypsinogen is not converted to trypsin
Answer/Explanation
Ans. (c)
The parietal cells (oxyntic cells) are large and most numerous on the side walls of gastric glands. These secrete hydrochloric acid and castle intrinsic factor. The peptic cells(zymogen) of gastric glands secrete gastric digestive enzymes as proenzymes-pepsinogen and prorennin and small amount of gastric amylase and gastric lipase. The hydrochloric acid maintains a strongly acidic $\mathrm{pH}$ of about 1.5-2.5 in the stomach. $\mathrm{HCl}$ converts pepsinogen and prorennin to pepsin and rennin respectively.
Question
Secretin and cholecystokinin are digestive hormones. They are secreted in[CBSE AIPMT 2005]
(a) oesophagus
(b) ileum
(c) duodenum
(d) pyloric stomach
Answer/Explanation
Ans. (c)
Secretin and cholecystokinin (CCK) are two main gastrointestinal (GI) hormones secreted in duodenum of alimentary canal. CCK stimulates gall bladder contraction and thus increases the flow of bile salts into the intestine. Secretin stimulates the release of an alkaline pancreatic fluid that neutralises stomach acid as it enters the intestine.
Question
Duodenum has characteristic Brunner’s glands which secrete two hormones called [CBSE AIPMT 2004]
(a) kinase, oestrogen
(b) secretin, cholecystokinin
(c) prolactin, parathormone
(d) estradion, progesterone
Answer/Explanation
Ans. (b)
Brunner’s gland secrete large amount of mucus and bicarbonates to protect duodenal mucosa and to neutralise the acidic chyme. It also secretes two hormones :
(a) Secretin
(b) Cholecystokinin (CCK) These stimulate:
(i) Secretion of pancreatic juice by pancreas.
(ii) Release of bile from gall bladder.
(iii) Formation of bile by liver and pancreatic juice.
Question
During prolonged fasting, in what sequence are the following organic compounds used up by the body? [CBSE AIPMT 2003]
(a) First carbohydrates, next proteins and lastly lipids
(b) First proteins, next lipids and lastly Icarbohydrates
(c) First carbohydrates, next fats and lastly proteins
(d) First fats, next carbohydrates and lastly proteins
Answer/Explanation
Ans. (c)
During prolonged fasting, first of all carbohydrates are utilised which include glycogen stored in liver. This is followed by the breakdown of adipose tissue, thus providing lipids and lastly the body utilises proteins.
Question
A certain person eats boiled potato; one of the food component in it is [CBSE AIPMT 2000]
(a) lactose which is indigestible
(b) starch which does not get digested
(c) cellulase which is digested by intestinal cellulase
(d) DNA which gets digested by pancreatic DNAase
Answer/Explanation
Ans. (d)
Anything which cannot be digested cannot serve as ‘food’. Therefore, starch and lactose in the present case have been automatically deleted. Cellulose cannot be digested by human beings, thus option (c) also stands rejected. Pancreatic juice can digest DNA which is the component of every cell.
Question
Cholecystokinin and duocrinin are secreted by [CBSE AIPMT 1999]
(a) adrenal cortex
(b) thyroid gland
(c) pancreas
(d) intestine
Answer/Explanation
Ans. (d)
Both cholecystokinin and duocrinin are hormones secreted by the intestine, while the former stimulates the gall bladder to release bile and pancreas to release enzyme mixture, the latter regulates the release of mucus from Brunner’s glands.
Question
Which part of body secretes the hormone secretin? [CBSE AIPMT 1999]
(a) Desophagus
(b) Duodenum
(c) Stomach
(d) lleum
Answer/Explanation
Ans. (b)
Secretin is a polypeptide hormone secreted by the mucosa of duodenum and jejunum. It perform two functions :
(a) It stimulates sodium bicarbonate from the pancreas which neutralises the acid in the chyme so that it will not damage the wall of the small intestine.
(b) It increases the rate of bile secretion in the liver.
Question
The hormone that stimulates the stomach to secrete gastric juice is [CBSE AIPMT 1998]
(a) gastrin
(b) renin
(c) enterokinase
(d) enterogasterone
Answer/Explanation
Ans. (a)
The stomach controls the production of gastric juice by means of a digestive homone called gastrin. It is produced by endocrine (hormone secreting) cells that are scattered throughout the epithelium of the stomach.
Question
Lactose is composed of [CBSE AIPMT 1998]
(a)glucose + fructose
(b)glucose + glucose
(c)glucose + galactose
(d) fructose + galactose
Answer/Explanation
Ans. (c)
Lactose $\left(\mathrm{C}_{\mathrm{ta}} \mathrm{H}_2 \mathrm{O}_{\mathrm{n}}\right)$ is a disaccharide found in mammalian milk. It comprises galactose and glucose units which are linked together by $\beta, 1-4$ glycosidic bonds. It is a reducing sugar.
Question
In vertebrates lacteals are found in [CBSE AIPMT 1998]
(a) ileum
(b) ischium
(c) oesophagous
(d) ear
Answer/Explanation
Ans. (a)
Lacteals are found in ileum they are Iymph vessels draining villi of vertebrate small intestine. After digestion, reconstituted fats are released into lacteals as chylomicrons.
Question
The contraction of gall bladder is due to [CBSE AIPMT 1998]
(a) gastrin
(b) secretin
(c) cholecystokinin
(d) enterogasterone
Answer/Explanation
Ans. (c)
Cholecystokinin (also called pancreozymin) is a hormone of mucosa of small intestine. It is released in response to chyme. It causes pancreas to release pancreatic enzymes and gall bladder to eject bile.
Question
If pancreas is removed, the compound which remain undigested is [CBSE AIPMT 1997]
(a) carbohydrates
(b) fats
(c) proteins
(d) All of these
Answer/Explanation
Ans. (d)
Pancreas secretes pancreatic juice which contain enzymes that acts on proteins, carbohydrates and fats. Enzymes of pancreatic juice are
(a) Pancreatic amylase which acts on starch and glycogen (polysaccharides).
(b) Trypsin, chymotrypsin and carboxypeptidases, which act on proteins and lipase which acts on triglycerides and converts it into fatty acids and glycerol.
If pancreas is removed from the body. the digestion of all these wauld nat occur.
Question
Which one of the following vitamin can be synthesised by bacteria inside the gut? [CBSE AIPMT 1997]
(a) $B_1$
(b) $\mathrm{C}$
(c) 0
(d) $K$
Answer/Explanation
Ans. (d)
Vitamin-K $K_2$ (menaquinone) It is formed by bacteria in the gut, while vitamin $K_T$ (phylloquinone) is found in green plant leaves.
Vitamin- $\mathbf{B}_1$ (thiamine) It acts as TPP-coenzyme for decarboxylases. Vitamin-C (ascorbic acid). It helps in development of teeth gums and maintenance of capillary wall.
Vitamin-D (calciferol). It helps in maintenance of calcium and phosphorus balance within the body.
Question
Which one of the following is a matching pair of a substrate and its particular digestive enzyme? [CBSE AIPMT 1996]
(a)Maltose – Maltase
(b) Lactose – Rennin
(c) Starch – Steapsin
(d) Casein – Chymotrypsin
Answer/Explanation
Ans. (a)
Intestinal juices contain a number of oligasaccharidase which hydrolyse the specific oligosaccharides into their monosaccharides. Maltase is one of them, which hydrolyses maltose into two glucose molecules.
Question
The enzyme enterokinase helps in the conversion of [CBSE AIPMT 1995]
(a) pepsinogen into pepsin
(b) trypsinogen into trypsin
(c) caseinogen into casein
(d) proteins into polypeptides
Answer/Explanation
Ans. (b)
Enterokinase helps in conversion of trypsinogen into trypsin in small intestine, which is an endoproteolytic enzyme and hydrolyses the peptones and proteoses into peptides.
Question
Rennin acts on [CBSE AIPMT 1994, 2000]
(a) milk changing casein into calcium paracaseinate at $7.2-8.2 \mathrm{pH}$
(b) protein in stomach
(c) fat in intestine
(d) milk changing casein into calcium paracaseinate at 1-3 $\mathrm{pH}$
Answer/Explanation
Ans. (d)
Stomach secretes gastric juice $\mathrm{pH}$ [1-3.5] which contains prorennin secreted by the zymogen cells. Inactive prorennin is converted into rennin by HCl. Rennin acts on casein, a protein milk changing it into calcium paracaseinate, it is known as curdling of. milk
Question
Inhibition of gastric and stimulation of gastric, pancreatic and bile secretions are controlled by hormones [CBSE AIPMT 1994]
(a) gastrin, secretin, enterokinin and chalecystokinin
(b) enterogasterone, gastrin, pancreozymin and cholecystokinin
(c) gastrin, enterogasterone, chalecystokinin and pancreozymin
(d) secretin, enterogasterone, gastrin and enterokinin
Answer/Explanation
Ans. (b)
Enterogasterone harmane secreted by mucosa of duodenum inhibits secretion of gastric juices and slows down the gastric movements. Gastrin is the hormone secreted by G-cells/argentaffin cells of pyloric region of stomach and stimulates the gastric glands to secrete gastric juices. Pancreozymin is secreted by mucosa of duodenum and stimulates the acinal cells of pancreas to secrete pancreatic enzymes. Cholecystokinin is secreted by cells of mucosa of duodenum and stimulates contraction of gall bladder to release bile.
Question
Most of the fat digestion occurs in [CBSE AIPMT 1993]
(a) rectum
(b) stomach
(c) duodenum
(d) small intestine
Answer/Explanation
Ans. (d)
Fats are emulsified in small intestine by the detergent action of bile salts. Emulsification of fat converts large fat droplets into large number of small droplets, which provide larger surface area to lipases. Then pancreatic lipase (steapsin) which is principal fat digesting enzyme, digest about $2 / 3^{\text {rd }}$ af fats in these stages.
Then intestinal lipase hydrolyses some tri, di and monoglycerides to fatty acids and glycerol molecules. So, the most of fat digestion occurs in small intestine.
Question
Secretion of gastric juice is stopped by [CBSE AIPMT 1993]
(a) gastrin
(b) pancreozymin
(c) cholecystokinin
(d) enterogasterone
Answer/Explanation
Ans. (d)
Enteragasterone is produced by small intestine and slows down the secretion of gastric juice and decreases the gastric movements.
Question
Where is protein digestion accomplished? [CBSE AIPMT 1991]
(a) Stomach
(b) lleum
(c) Rectum
(d) Duodenum
Answer/Explanation
Ans. (b)
The cells that line the ileum contain the protease and carbohydrase enzymes responsible for the final stages of protein and carbohydrate digestion. These enzymes are present in the cytoplasm of the epithelial cells.
Question
Release of pancreatic juice is stimulated by [CBSE AIPMT 1990, 89]
(a)enterokinase
(b)cholecystokinin
(c) trypsinogen
(d) secretin
Answer/Explanation
Ans. (d)
Secretin is secreted by $\delta$-cells of mucasa of duodenum which stimulates pancreas and controls the volume of pancreatic juice including water and electrolytes.
Question
Pancreas produces [CBSE AIPMT 1991]
(a) three digestive enzymes and one hormane
(b) three digestive enzymes and two hormanes
(c) two digestive enzymes and one hormone
(d) three digestive enzymes and no hormone
Answer/Explanation
Ans. (b)
Pancreas produces pancreatic juice which contains trypsinogen, chymotrypsin, carboxypeptidases, lipase, pancreatic $\alpha$-amylase, elastage, nucleases. Dut of these enzymes, the first three are concerned with protein digestion which finally converts protein into small peptides. Pancreas also secretes insulin and glucagon hormones which acts antagonastically in controlling the blood sugar level.
Question
Emulsification of fat will not occur in the absence of [CBSE AIPMT 1990]
(a) lipase
(b) bile pigments
(c) bile salts
(d) pancreatic juice
Answer/Explanation
Ans. (c)
Bile is a watery greenish fluid containing bile salts, bile pigments, cholesterol and phospholipid. Bile salts play an important role in digestion of fats. Therefore in their absence emulsification of fat cannot take place.