Gastro intestinal hormones/Digestive enzymes Questions in English

(C) The correct answer is $C$ (Secretin).
Secretin is a hormone produced by the $S$-cells of the duodenum in the gastrointestinal tract.
It primarily stimulates the pancreas to secrete water and bicarbonate ions into the small intestine to neutralize acidic chyme.
Additionally,it also acts on the liver to stimulate the secretion of bile.
Thus,it stimulates two organs: the pancreas and the liver.

(B) Cholecystokinin $(CCK)$ is a peptide hormone primarily secreted by the $I$-cells in the mucosal epithelium of the small intestine,specifically in the duodenum and jejunum.
Its primary functions include stimulating the release of digestive enzymes from the pancreas and the contraction of the gallbladder to release bile into the small intestine,which aids in the digestion of fats and proteins.

(D) Assertion $(A)$ is incorrect because Secretin acts on the exocrine pancreas to stimulate the secretion of water and bicarbonate ions,not the gall bladder.
Reason $(R)$ is correct because Cholecystokinin $(CCK)$ acts on the pancreas to stimulate the secretion of pancreatic enzymes and on the gall bladder to stimulate the contraction and release of bile juice.
Therefore,$A$ is incorrect and $R$ is correct.

(C) Enzymes are biocatalysts that exhibit optimal activity at specific $pH$ levels.
Proteases,such as pepsin found in the stomach,are specifically adapted to function optimally in highly acidic environments (low $pH$ range of $1.5$ to $2.5$).
Lipases and most carbohydrases typically function optimally at neutral or slightly alkaline $pH$ levels found in the small intestine.
Therefore,among the given options,proteases are the enzymes that are optimally active at an acidic $pH$.

(D) The secretion of pancreatic juice is primarily regulated by gastrointestinal hormones.
$1$. $Secretin$ acts on the exocrine pancreas to stimulate the secretion of water and bicarbonate ions.
$2$. $Cholecystokinin$ $(CCK)$ stimulates the pancreas to secrete digestive enzymes.
Since both hormones are involved,and $Secretin$ is the primary hormone known for stimulating the watery component of pancreatic juice,in many contexts,both are considered correct. However,$Secretin$ is the classic answer for the stimulation of pancreatic juice secretion (specifically the bicarbonate-rich fluid).
Therefore,the most appropriate answer is $Secretin$.

(D) The secretion of gastric juice is primarily regulated by both neural and hormonal mechanisms.
$1$. Gastrin is a hormone that stimulates the secretion of gastric juice.
$2$. Enterogastrone (also known as Gastric Inhibitory Peptide or $GIP$) is a hormone secreted by the duodenal mucosa when fatty acids and acidic chyme enter the duodenum.
$3$. This hormone acts to inhibit the secretion of gastric juice and reduces gastric motility,allowing more time for digestion in the small intestine.
Therefore,the correct answer is $D$.

(C) The regulation of the digestive system is mediated by gastrointestinal hormones:
$1$. Gastrin stimulates the secretion of $HCl$ and pepsinogen in the stomach.
$2$. Enterogastrone (also known as Gastric Inhibitory Peptide or $GIP$) inhibits gastric secretion and motility.
$3$. Cholecystokinin $(CCK)$ stimulates the release of bile from the gallbladder and pancreatic enzymes from the pancreas.
$4$. Pancreozymin stimulates the secretion of pancreatic enzymes.
Therefore,the correct sequence of hormones involved in the inhibition of gastric secretion and the regulation of gastric,pancreatic,and bile secretions is Gastrin,Enterogastrone,Cholecystokinin,and Pancreozymin.

(B) The enzyme $Enterokinase$ (also known as $Enteropeptidase$) is secreted by the intestinal mucosa.
It acts on the inactive enzyme $Trypsinogen$,which is secreted by the pancreas into the duodenum.
$Enterokinase$ converts $Trypsinogen$ into its active form,$Trypsin$.
$Trypsin$ then activates other pancreatic enzymes like $Chymotrypsinogen$ and $Procarboxypeptidase$ to facilitate protein digestion.

(A) The correct match is $Maltose - Maltase$.
$Maltase$ is a specific enzyme that hydrolyzes the disaccharide $Maltose$ into two molecules of $Glucose$.
$Lactose$ is broken down by $Lactase$,not $Renin$.
$Starch$ is primarily broken down by $Amylase$ (Steapsin is another name for pancreatic lipase,which acts on fats).
$Casein$ is a milk protein primarily acted upon by $Renin$ in infants or $Pepsin$ in adults,not $Chymotrypsin$.

(C) The contraction of the gallbladder and the relaxation of the sphincter of Oddi are primarily stimulated by the hormone $Cholecystokinin$ $(CCK)$.
$CCK$ is secreted by the $I$-cells in the mucosal epithelium of the small intestine in response to the presence of fats and proteins in the chyme.
Once released into the bloodstream, it travels to the gallbladder, triggering its contraction to release bile into the duodenum to aid in fat digestion.

(A) The hormone $Gastrin$ is secreted by the $G-cells$ located in the pyloric antrum of the stomach.
It acts on the gastric glands to stimulate the secretion of gastric juice,which includes $HCl$ and pepsinogen.
$Renin$ is a proteolytic enzyme found in the gastric juice of infants.
$Enterokinase$ is an enzyme secreted by the intestinal mucosa that activates trypsinogen.
$Enterogastrone$ is a hormone that inhibits gastric secretion and motility.

(D) Cholecystokinin $(CCK)$ and duocrinin are gastrointestinal hormones.
$CCK$ is secreted by the $I$-cells of the duodenal and jejunal mucosa.
Duocrinin is secreted by the mucosa of the duodenum.
Both of these hormones are produced by the endocrine cells located in the wall of the small intestine.
Therefore,the correct option is $D$.

(D) Boiled potatoes are a rich source of starch.
In the human digestive system,starch is broken down into simpler sugars (like maltose) by the action of salivary amylase in the mouth and pancreatic amylase in the small intestine.
Therefore,starch is a digestible component of food.
However,cellulose is a structural polysaccharide found in plant cell walls that humans cannot digest because we lack the enzyme cellulase.
$DNA$ is present in all plant cells,and it is broken down by pancreatic $DNAase$ into nucleotides in the small intestine.
Among the given options,$DNA$ is a component that is specifically digested by pancreatic $DNAase$.

(B) The duodenum secretes two primary hormones,$Secretin$ and $Cholecystokinin$ $(CCK)$,which play a crucial role in the digestive process.
$Secretin$ stimulates the pancreas to release bicarbonate-rich pancreatic juice and also stimulates the Brunner's glands (located in the submucosa of the duodenum) to secrete mucus and enzymes.
$Cholecystokinin$ $(CCK)$ stimulates the gallbladder to release bile and the pancreas to release digestive enzymes.
Therefore,the correct option is $B$.

(B) Secretin and cholecystokinin $(CCK)$ are gastrointestinal hormones.
These hormones are secreted by the endocrine cells present in the mucosa of the duodenum.
Secretin stimulates the exocrine pancreas to secrete bicarbonate ions,while $CCK$ stimulates the gallbladder to release bile and the pancreas to secrete digestive enzymes.
Therefore,the correct site of secretion is the duodenum.

(C) In humans,specifically in infants,the stomach secretes an enzyme called $Rennin$ (also known as $Chymosin$).
This enzyme is responsible for the digestion of milk proteins,specifically $Casein$.
$Rennin$ converts soluble milk protein $Casein$ into insoluble $Paracasein$ (calcium paracaseinate),which is then further digested by $Pepsin$.

(A) The secretion of pancreatic juice and bicarbonate is regulated by hormones produced in the duodenum.
$1$. $Secretin$ acts on the exocrine pancreas to stimulate the secretion of water and bicarbonate ions.
$2$. $Cholecystokinin$ $(CCK)$ acts on the pancreas to stimulate the secretion of pancreatic enzymes.
Therefore,both $Cholecystokinin$ and $Secretin$ are responsible for the stimulation of pancreatic secretions.

(B) Lipases are enzymes that catalyze the hydrolysis of fats (lipids) into fatty acids and glycerol. Amylase breaks down starch into sugars. Protease breaks down proteins into amino acids. Disaccharidase breaks down disaccharides into monosaccharides. Therefore,the pairing of Lipase with starch is incorrect.

(D) Sugarcane and sugarbeet are the richest sources of sucrose,which is a disaccharide.
In the human digestive system,the enzyme invertase (also known as sucrase) is present in the duodenum of the small intestine.
This enzyme hydrolyzes sucrose into one molecule of glucose and one molecule of fructose.
Option $A$ is incorrect because pepsin acts on proteins.
Option $B$ is incorrect because salivary amylase acts on starch to produce maltose,not glucose.
Option $C$ is incorrect because lipases act on triglycerides to produce fatty acids and monoglycerides.
Therefore,option $D$ correctly describes the enzymatic breakdown of sucrose.

(D) Milk protein (casein) can be digested by both pepsin and chymotrypsin. Pepsin is a proteolytic enzyme found in the stomach that acts on proteins,including casein. Chymotrypsin is a pancreatic enzyme that also breaks down proteins,including casein. Therefore,the statement that chymotrypsin can digest casein is correct.

(C) Pancreatic amylase is a carbohydrate-digesting enzyme (amylolytic enzyme) that hydrolyzes starch and glycogen into maltose,isomaltose,and limit dextrins.
Proteins are digested by proteolytic enzymes such as trypsin,chymotrypsin,and carboxypeptidase,not by amylase.
Therefore,the Assertion is correct,but the Reason is incorrect.

(A) Trypsin is a protein-digesting enzyme present in the intestine of animals.
In predator animals that consume the blood of their prey,trypsin hydrolyzes the $fibrinogen$ present in the blood into $fibrin$.
This process leads to blood coagulation,which facilitates the digestion of blood proteins.
Therefore,both the Assertion and the Reason are correct,and the Reason is the correct explanation of the Assertion.

(C) The Assertion is correct because $ptyalin$ (salivary amylase) acts on starch and converts it into maltose.
The Reason is incorrect because $sucrase$ (invertase) hydrolyses sucrose into glucose and fructose,not lactose. Lactose is hydrolysed by the enzyme $lactase$ into glucose and galactose.

(N/A) The enzyme trypsin (present in the pancreatic juice) activates the inactive enzyme chymotrypsinogen into chymotrypsin.
$\text{Chymotrypsinogen (Inactive)} \xrightarrow{\text{Trypsin}} \text{Chymotrypsin (Active)}$
The activated chymotrypsin plays an important role in the further breakdown of partially-hydrolysed proteins into peptides.
$\text{Proteins} \xrightarrow{\text{Chymotrypsin}} \text{Peptides}$
The other digestive enzymes of the same category (proteases) secreted by the pancreas are trypsinogen and carboxypeptidase.
Trypsinogen is present in an inactive form in the pancreatic juice. The enzyme enterokinase,secreted by the intestinal mucosa,activates trypsinogen into trypsin.
$\text{Trypsinogen} \xrightarrow{\text{Enterokinase}} \text{Trypsin} + \text{Inactive peptide}$
The activated trypsin then further hydrolyses the remaining trypsinogen and activates other pancreatic enzymes such as chymotrypsinogen and carboxypeptidase. Trypsin also helps in breaking down proteins into peptides.
$\text{Proteins} \xrightarrow{\text{Trypsin}} \text{Peptides}$
Carboxypeptidases act on the carboxyl end of the peptide chain and help in releasing the last amino acids.
$\text{Peptides} \xrightarrow{\text{Carboxypeptidase}} \text{Small peptide chain} + \text{Amino acids}$

(N/A) The activities of the gastrointestinal tract are under neural and hormonal control for the proper coordination of different parts.
The sight,smell,and/or the presence of food in the oral cavity can stimulate the secretion of saliva.
Gastric and intestinal secretions are also similarly stimulated by neural signals. The muscular activities of different parts of the alimentary canal are moderated by neural mechanisms,both local and through the $CNS$.
Hormonal control of the secretion of digestive juices is carried out by local hormones produced by the gastric and intestinal mucosa.

$1$. Hormone	$2$. Function
Gastrin	Induces secretion of gastric juice.
Pancreozymin	Induces secretion of pancreatic enzymes.
Secretin	Induces secretion of water and bicarbonate ions in pancreatic juice.
Cholecystokinin $(CCK)$	Induces secretion of bile juice and pancreatic enzymes.
Enterogastrone/Gastric Inhibitory Peptide $(GIP)$	Inhibits gastric secretion and motility.

(N/A) The activities of the gastrointestinal tract are under neural and hormonal control for proper coordination of different parts.
Hormonal control of the secretion of digestive juices is carried out by local hormones produced by the gastric and intestinal mucosa.

$1$. Hormone	$2$. Function
Gastrin	Acts on the gastric glands and stimulates the secretion of hydrochloric acid and pepsinogen.
Secretin	Acts on the exocrine pancreas and stimulates the secretion of water and bicarbonate ions.
Cholecystokinin $(CCK)$	Acts on both the pancreas and the gallbladder and stimulates the secretion of pancreatic enzymes and bile juice,respectively.
Gastric Inhibitory Peptide $(GIP)$	Inhibits gastric secretion and motility.

(C) The activities of the gastrointestinal tract are under neural and hormonal control for proper coordination of different parts.
The endocrine cells present in different parts of the gastrointestinal tract secrete four major peptide hormones: Gastrin,Secretin,Cholecystokinin $(CCK)$,and Gastric Inhibitory Peptide $(GIP)$.
Gastrin acts on the gastric glands and stimulates the secretion of $HCl$ and pepsinogen. Secretin acts on the exocrine pancreas and stimulates the secretion of water and bicarbonate ions. $CCK$ stimulates the secretion of pancreatic enzymes and bile juice.

(N/A)

Pepsinogen	Trypsinogen
$(1)$ It is produced by the gastric glands in the stomach.	$(1)$ It is produced by the pancreas.
$(2)$ It is an inactive proteolytic enzyme present in gastric juice.	$(2)$ It is an inactive proteolytic enzyme present in pancreatic juice.
$(3)$ It is activated into pepsin by dilute $HCl$.	$(3)$ It is activated into trypsin by the enzyme enterokinase.
$(4)$ It helps in the conversion of proteins into proteoses and peptones.	$(4)$ It helps in the conversion of proteins,proteoses,and peptones into dipeptides.

(N/A) $(1)$ Ptyalin (Salivary Amylase) is an enzyme present in saliva. It initiates the chemical digestion of carbohydrates by partially breaking down starch into maltose.
$(2)$ Renin is a proteolytic enzyme found in the gastric juice of infants. It plays a crucial role in the digestion of milk proteins by converting the soluble milk protein caseinogen into insoluble casein (curd),which is then further digested by pepsin.

(N/A) $(1)$ Enterokinase is an enzyme secreted by the intestinal mucosa (specifically the duodenum). It plays a crucial role in the activation of pancreatic enzymes by converting inactive trypsinogen into active trypsin.
$(2)$ Gastric Inhibitory Peptide $(GIP)$ is a hormone secreted by the duodenal mucosa. Its primary function is to inhibit gastric secretion and motility,thereby regulating the digestive process.

(C) The activities of the gastrointestinal tract are regulated by both neural and hormonal control to ensure the proper coordination of different parts.
Neural control is mediated by the local enteric nervous system and the autonomic nervous system.
Hormonal control is mediated by various gastrointestinal hormones (such as gastrin,secretin,and cholecystokinin) secreted by the endocrine cells of the gastrointestinal mucosa.

(C) The enzyme enterokinase is secreted by the intestinal mucosa. It acts on the inactive enzyme trypsinogen,which is secreted by the pancreas,and converts it into its active form,trypsin. This activation is a crucial step in the protein digestion process in the small intestine.

(B) Rennin is a proteolytic enzyme found in the gastric juice of infants. It specifically hydrolyses the milk protein casein into paracasein,which then reacts with calcium ions to form calcium paracaseinate (curd),facilitating the digestion of milk.

(A) Amylase is an enzyme that acts on starch (a polysaccharide) and hydrolyzes it into simpler sugars like glucose or maltose. In the context of complete hydrolysis,amylase facilitates the breakdown of starch into glucose units.

(A) The secretion of gastric juice is primarily regulated by the hormone $Gastrin$.
$Gastrin$ is secreted by the $G$-cells located in the pyloric antrum of the stomach and the duodenal mucosa in response to the presence of proteins,peptides,and alcohol.
Once released into the bloodstream,$Gastrin$ acts on the gastric glands to stimulate the secretion of large amounts of gastric juice,which contains $HCl$ and pepsinogen.
Therefore,$Gastrin$ is the key hormonal regulator of gastric secretion.

(D) Cholecystokinin-pancreozymin $(CCK-PZ)$ is a hormone secreted by the epithelium of the small intestine.
It stimulates the gall bladder to contract and release bile into the duodenum.
Simultaneously,it stimulates the pancreas to secrete and release digestive enzymes into the pancreatic juice.

(C) Pepsin is inactivated at $pH$ above $5$.
Pepsin is a proteolytic or protein-splitting enzyme.
The optimum $pH$ for pepsin activity is approximately $2$,allowing it to function effectively in the highly acidic environment of the gastric juice.
Conversely,it becomes inactivated in a near-basic medium.

(A) Digestive enzymes are classified as hydrolases because they catalyze the hydrolysis of chemical bonds. Hydrolysis is a reaction where a water molecule is added to break down complex molecules like proteins,carbohydrates,and fats into their simpler,absorbable forms.

(C) Bile salts are essential for the emulsification of fats,which increases the surface area for the action of enzymes.
Lipase is the enzyme responsible for the digestion of fats into di- and monoglycerides.
Bile salts act as an activator or co-factor for lipase,significantly enhancing its catalytic activity in the small intestine.
Therefore,bile salts facilitate the action of lipase on emulsified fats.

(B) Enterogastrone is a gastrointestinal hormone that regulates digestive secretions along with other hormones like gastrin,secretin,and cholecystokinin.
Enterogastrone functions by slowing down gastric contractions and inhibiting gastric acid secretion.
Due to this inhibitory effect on the stomach,it is also known as Gastric Inhibitory Peptide $(GIP)$.

(C) Secretin and cholecystokinin $(CCK)$ are two main gastrointestinal $(GI)$ hormones secreted in the duodenum of the 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 neutralizes stomach acid as it enters the intestine.

(D) Secretin is a peptide hormone produced by the $S$-cells of the duodenum mucosa. It is released in response to the acidic chyme entering the small intestine from the stomach. Its primary function is to stimulate the pancreas to secrete bicarbonate-rich pancreatic juice,which helps neutralize the acidity of the chyme. It also stimulates the liver to increase bile production.

(D) The functions described are as follows:
$I.$ Enterokinin stimulates the crypts of Lieberkuhn to secrete intestinal juice (succus entericus).
$II.$ Somatostatin is a hormone that inhibits the secretion of both insulin and glucagon from the pancreas (specifically from alpha and beta cells).
$III.$ Duocrinin stimulates the Brunner's glands (located in the duodenum) to release mucus and bicarbonate-rich fluid to protect the duodenal wall from acidic chyme.
Therefore,the correct matching is $I$-Enterokinin,$II$-Somatostatin,and $III$-Duocrinin.

(D) Gastric juice contains pepsinogen (which is converted to pepsin),gastric lipase,and in infants,rennin (chymosin).
$1$. Amylase is found in saliva (mouth) and pancreatic juice.
$2$. Trypsin and carboxypeptidase are enzymes found in pancreatic juice,not in gastric juice.

(C) Ptyalin,also known as salivary amylase,is an enzyme present in saliva that breaks down starch into simpler sugars.
It requires the presence of chloride ions $(Cl^-)$ as an essential cofactor for its catalytic activity.
The reaction in the mouth is as follows:
$\text{Starch} \xrightarrow[pH = 6.8]{\text{Ptyalin}, Cl^-} \text{Maltose} + \text{Isomaltose} + \text{Dextrins}$

(B) $Trypsin$ is a digestive enzyme,whereas $Gastrin$,$Secretin$,and $Enterocrinin$ are gastrointestinal hormones. Therefore,$Trypsin$ is the odd one out.

(A) Cholagogues are substances that promote the flow of bile into the duodenum.
They stimulate the contraction of the gall bladder and the relaxation of the sphincter of Oddi.
This process is mediated by the hormone Cholecystokinin-Pancreozymin $(CCK-PZ)$,which is released from the mucosal cells of the duodenum in response to the presence of fats and proteins.
Therefore,the release of $CCK-PZ$ is the mechanism by which cholagogues induce gall bladder contraction.
Thus,both the Assertion and the Reason are correct,and the Reason is the correct explanation of the Assertion.

(A) Trypsin is a proteolytic enzyme secreted by the pancreas in an inactive form called trypsinogen.
It is classified as an endopeptidase because it specifically cleaves peptide bonds within the interior of a polypeptide chain,rather than at the terminal ends.
Since the enzyme's function as an endopeptidase is defined by its ability to act on interior peptide bonds,the Reason correctly explains the Assertion.

(D) Gastrin is a peptide hormone primarily secreted by the $G$-cells located in the pyloric antrum of the stomach.
It stimulates the parietal cells to secrete hydrochloric acid $(HCl)$ and also promotes the secretion of pepsinogen,which together constitute the gastric juice.
Therefore,it plays a crucial role in the regulation of gastric acid secretion.