Gastro intestinal hormones/Digestive enzymes Questions in English

(A) Enterogastrone is a hormone secreted by the duodenal mucosa.
It acts to inhibit gastric secretion (including $HCl$ from parietal cells) and reduces gastric motility (contractions) when chyme enters the duodenum.
Therefore,the correct option is $A$.

(C) $Enterogastrone$ is a hormone secreted by the duodenal mucosa that inhibits gastric secretion and gastric motility.
It acts as a negative feedback mechanism to slow down the emptying of the stomach when chyme enters the small intestine.

(B) $Enterogastrone$ is a hormone secreted by the duodenal mucosa when fats are present in the intestine.
Its primary function is to inhibit the secretion of gastric juice and reduce gastric motility.
This allows more time for the digestion and absorption of fats in the small intestine.
Therefore,the correct option is $B$.

(D) Enterokinase (also known as enteropeptidase) is an enzyme secreted by the intestinal mucosa. Its primary function is to convert the inactive pancreatic enzyme trypsinogen into its active form,trypsin. Once trypsin is activated,it further activates other pancreatic enzymes like chymotrypsinogen and procarboxypeptidase,which are essential for protein digestion. Therefore,the process activated by enterokinase is the conversion of trypsinogen to trypsin.

(B) Rennin (also known as chymosin) is a proteolytic enzyme found in the gastric juice of infants.
It acts on the milk protein casein (a soluble protein) and converts it into insoluble calcium paracaseinate (paracasein).
This process is essential for the digestion of milk in infants,as it prevents the milk from passing too quickly through the digestive tract,allowing other enzymes to act on it effectively.

(B) In the human digestive system,$HCl$ (Hydrochloric acid) acts as an activator that converts the inactive zymogen $Pepsinogen$ into the active enzyme $Pepsin$.
Similarly,$Enterokinase$ (also known as $Enteropeptidase$) is an enzyme secreted by the intestinal mucosa that activates the inactive pancreatic zymogen $Trypsinogen$ into the active enzyme $Trypsin$.

(A) In an adult human,$Rennin$ (also known as chymosin) is typically absent or present in negligible amounts. $Rennin$ is a proteolytic enzyme found in the gastric juice of infants that helps in the digestion of milk proteins $(casein)$.
$Renin$ is a hormone/enzyme produced by the kidneys that regulates blood pressure.
$Trypsin$ and $Pepsin$ are major digestive enzymes found in the digestive tract of adults.
Therefore,$Rennin$ is the odd one out as it is primarily associated with infants,not adults.

(D) $1$. $Enterokinase$ is an enzyme secreted by the intestinal mucosa that activates trypsinogen into trypsin.
$2$. $Amylase$ is a digestive enzyme that breaks down starch into sugars.
$3$. $Trypsin$ is a proteolytic enzyme secreted by the pancreas in its inactive form,trypsinogen.
$4$. $Enterogastrone$ is a hormone,not an enzyme. It is secreted by the duodenal mucosa and inhibits gastric secretion and motility.

(B) The hormone $Gastrin$ is produced by the $G$-cells in the stomach lining.
It acts on the gastric glands to stimulate the secretion of $HCl$ (hydrochloric acid) and pepsinogen.
$Renin$ is an enzyme involved in blood pressure regulation.
$Secretin$ stimulates the pancreas to secrete water and bicarbonate ions.
$Somatomedin$ (also known as $IGF-1$) is involved in growth regulation.
Therefore,the correct option is $B$.

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

(A) $Pepsin$ is a proteolytic enzyme secreted by the chief cells of the stomach in the form of an inactive precursor called $pepsinogen$.
In the presence of $HCl$ (hydrochloric acid),$pepsinogen$ is converted into its active form,$Pepsin$.
$Pepsin$ is highly specific to an acidic environment and shows maximum catalytic activity within the $pH$ range of $1.20$ to $1.80$.
If the $pH$ increases significantly above this range,the enzyme becomes inactive.

(C) Trypsinogen is an inactive enzyme (zymogen) secreted by the pancreas into the small intestine.
It is activated into its active form,trypsin,by an enzyme called enterokinase (also known as enteropeptidase).
Enterokinase is secreted by the intestinal mucosa.
Once formed,trypsin further activates other pancreatic zymogens like chymotrypsinogen and procarboxypeptidase.

(B) Enterogastrone is a hormone secreted by the duodenal mucosa that inhibits the secretion of gastric acid $(HCl)$ and reduces gastric motility.
It acts as a feedback mechanism to slow down the emptying of the stomach when the duodenum is full or when the acidity is high.
Secretin primarily stimulates the pancreas to release bicarbonate ions.
Enterocrinin stimulates the secretion of intestinal juice.
Gastrin stimulates the secretion of $HCl$ and pepsinogen in the stomach.
Therefore,the correct option is $B$.

(A) Digestive enzymes are biological catalysts that break down complex food molecules into simpler forms.
Most digestive enzymes belong to the class of $Hydrolases$,as they catalyze the hydrolysis of chemical bonds (e.g.,proteins,carbohydrates,and fats).
$Oxidoreductases$ are involved in redox reactions,not primarily in digestion.
$Enterogastrone$ is a hormone,not an enzyme.
Therefore,$Hydrolase$ is the correct classification for digestive enzymes.

(A) Chymotrypsin is a digestive enzyme that belongs to the class of proteases.
It is secreted by the pancreas in an inactive form called chymotrypsinogen.
In the small intestine,it is activated by trypsin and functions to break down proteins into smaller peptides by hydrolyzing peptide bonds.
Therefore,it is classified as a proteolytic enzyme.

(C) In mammals,the secretion of pancreatic juice is primarily regulated by two hormones: $Secretin$ and $Cholecystokinin$ $(CCK)$.
$Secretin$ acts on the exocrine pancreas to stimulate the secretion of water and bicarbonate ions.
$Cholecystokinin$ $(CCK)$ stimulates the acinar cells of the pancreas to secrete digestive enzymes.
Therefore,both hormones are involved in the regulation of pancreatic juice secretion.

(D) The hormone $Enterogastrone$ (also known as $Gastric$ $Inhibitory$ $Peptide$ or $GIP$) is released by the duodenal mucosa.
Its primary function is to inhibit gastric secretion and gastric motility, thereby slowing down the emptying of the stomach into the small intestine.
$Gastrin$ stimulates gastric acid secretion, while $Secretin$ and $CCK$ primarily stimulate pancreatic and biliary secretions.

(A) Proteolytic enzymes are enzymes that break down proteins into smaller polypeptides or amino acids.
$1$. $Pepsin$ is a gastric enzyme that breaks down proteins into peptides.
$2$. $Trypsin$ and $Chymotrypsin$ are pancreatic enzymes that further break down peptides into smaller fragments in the small intestine.
Therefore,the correct group of proteolytic enzymes is $Trypsin, Chymotrypsin, Pepsin$.

(C) The contraction of the gallbladder is primarily stimulated by the hormone $Cholecystokinin$ $(CCK)$.
$CCK$ is secreted by the $I$-cells in the mucosal epithelium of the small intestine (duodenum and jejunum) in response to the presence of fats and proteins in the chyme.
Once released into the bloodstream, $CCK$ acts on the gallbladder to cause its contraction, which forces bile into the common bile duct and eventually into the duodenum to aid in the digestion and absorption of fats.

(A) Enterogastrone is a hormone secreted by the duodenal mucosa.
It acts to inhibit gastric secretion and motility.
It is released in response to the presence of fat in the duodenum.
Therefore,it is a hormone secreted by the mucosa of the digestive tract.

(C) The enzyme maltase is present in the small intestine and is responsible for the hydrolysis of maltose into two molecules of glucose.
This enzymatic reaction occurs in the intestinal juice (succus entericus),which is slightly alkaline in nature.
Therefore,the optimal $pH$ for the activity of maltase is slightly greater than $7$ (typically around $7.5$ to $8.0$).

(D) Aminopeptidase is a brush border enzyme found in the small intestine.
It acts on the $N$-terminal end of peptides.
It specifically hydrolyzes the peptide bonds at the $N$-terminal end of polypeptides or oligopeptides to release free amino acids.
Therefore,the final product of the action of aminopeptidase is amino acids.

(B) Enterokinase (also known as enteropeptidase) is an enzyme secreted by the intestinal mucosa. Its primary function is to activate trypsinogen,an inactive zymogen secreted by the pancreas,into its active form,trypsin. This activation is a critical step in the protein digestion process because trypsin subsequently activates other pancreatic zymogens like chymotrypsinogen and procarboxypeptidase.

(A) Gastrin is a peptide hormone that primarily stimulates the secretion of gastric juice (hydrochloric acid and pepsinogen) from the gastric glands in the stomach.
$Enterogastrone$ inhibits gastric secretion.
$Secretin$ stimulates the pancreas to secrete water and bicarbonate ions.
$Hepatocrinin$ stimulates the liver to secrete bile.

(B) The secretion of bile from the liver is primarily stimulated by the hormone $Secretin$.
$Secretin$ is produced by the $S$-cells of the duodenum in response to the acidic chyme entering from the stomach.
It acts on the liver to increase the production and secretion of bile into the bile ducts.
$Gastrin$ stimulates gastric acid secretion,$Enterogastrone$ inhibits gastric secretion,and $Enterokinase$ is an enzyme that activates trypsinogen.

(D) The brush border cells of the intestinal mucosa secrete enzymes that form the intestinal juice or succus entericus. These enzymes include disaccharidases (e.g.,maltase,lactase,sucrase),dipeptidases,nucleotidases,and nucleosidases. Lipases and steapsin (a pancreatic lipase) are primarily produced by the pancreas and are secreted into the small intestine,not by the brush border cells of the intestinal mucosa. Therefore,both $C$ and $D$ are not produced by the brush border cells,but in the context of standard biology questions,$D$ (Steapsin) is the specific pancreatic enzyme often highlighted as not being a brush border enzyme.

(A) Amylase is a digestive enzyme that breaks down complex carbohydrates into simpler sugars. Specifically,it acts on starch (a polysaccharide) to hydrolyze it into maltose and other smaller glucose units. Protein is acted upon by proteases (like pepsin or trypsin),and fats are acted upon by lipases.

(C) The hormone $Cholecystokinin$ $(CCK)$ is secreted by the duodenal mucosa.
It acts on both the pancreas and the gallbladder.
It stimulates the pancreas to secrete digestive enzymes and the gallbladder to contract,thereby releasing bile into the duodenum to aid in the digestion of fats.

(D) Rennin (also known as chymosin) is a proteolytic enzyme found in the gastric juice of infants. It plays a crucial role in the digestion of milk proteins (casein) by converting soluble casein into insoluble calcium paracaseinate,which allows for better digestion by pepsin. Therefore,it is secreted by the gastric glands located in the stomach.

(B) Secretin is a peptide hormone produced by the $S$-cells of the duodenum (part of the small intestine) in response to the acidic chyme entering from the stomach.
Its primary function is to stimulate the pancreas to secrete a bicarbonate-rich fluid,which neutralizes the acidity of the chyme in the duodenum,creating an optimal $pH$ for the activity of pancreatic enzymes.

(C) Secretin is a hormone produced by the $S$-cells of the duodenum in response to acidic chyme entering the small intestine.
Its primary function is to stimulate the pancreas to secrete water and bicarbonate ions into the duodenum to neutralize the acidity of the chyme.
Additionally,it also stimulates the liver to produce bile.
Among the given options,the most direct and primary target for secretin's stimulation regarding digestive secretions is the production of bile by the liver and pancreatic juice by the pancreas. However,in the context of standard biology curriculum,secretin is famously known for stimulating the production of pancreatic juice (bicarbonate-rich) and bile. Given the options,$C$ (Bile) is a correct physiological response,but $D$ (Pancreatic juice) is the most significant regulatory function. Since both are technically stimulated,we select $C$ as it is a classic textbook association for secretin's effect on the liver.

(D) The secretion of digestive juices is regulated by both neural and hormonal mechanisms.
$1$. $Gastrin$ stimulates the secretion of $HCl$ and pepsinogen in the stomach.
$2$. $Cholecystokinin$ $(CCK)$ stimulates the secretion of pancreatic enzymes and bile juice from the gallbladder.
$3$. $Enterogastrone$ (also known as $GIP$ or gastric inhibitory peptide) inhibits gastric secretion and motility.
Since all these hormones play a significant role in the regulation of digestive secretions, the correct answer is $All \text{ of the above}$.

(D) The gastrointestinal hormone $GIP$ stands for Gastric Inhibitory Peptide,also known as Glucose-dependent Insulinotropic Peptide.
It is secreted by the $K$-cells of the duodenum and jejunum.
Its primary function is to stimulate the release of insulin from the beta cells of the pancreas in response to the presence of glucose in the digestive tract.
Therefore,the correct option is $D$.

(A) The secretion of gastric juice is primarily stimulated by the hormone $Gastrin$.
$Gastrin$ is produced by the $G-cells$ in the stomach lining.
When food enters the stomach,$Gastrin$ is released into the bloodstream,which then stimulates the parietal cells to secrete $HCl$ and the chief cells to secrete pepsinogen,thereby promoting gastric juice secretion.
$Secretin$ and $Enterogastrone$ generally inhibit gastric secretion,while $Enterokinase$ is an enzyme involved in the activation of trypsinogen in the small intestine.

(B) $Secretin$ is a peptide hormone produced by the $S-cells$ of the duodenum in the small intestine.
It is released in response to the acidic $pH$ of the chyme entering the duodenum from the stomach.
Its primary function is to stimulate the exocrine portion of the pancreas to secrete water and bicarbonate ions $(HCO_3^-)$ into the duodenum to neutralize the acidity of the chyme.
Therefore,the correct option is $B$.

(B) The correct answer is $B$ (Ptyalin).
Gastrin,Glucagon,and Secretin are all hormones.
Gastrin is a hormone that stimulates gastric acid secretion.
Glucagon is a hormone that increases blood glucose levels.
Secretin is a hormone that stimulates the pancreas to release bicarbonate.
Ptyalin (also known as salivary amylase) is an enzyme,not a hormone.
Therefore,Ptyalin is the odd one out.

(C) Secretin and cholecystokinin $(CCK)$ are peptide hormones produced by the enteroendocrine cells located in the mucosa of the duodenum.
Secretin is released in response to low $pH$ (acidic chyme) in the duodenum and stimulates the pancreas to secrete bicarbonate ions.
Cholecystokinin $(CCK)$ is released in response to the presence of fats and proteins in the duodenum,stimulating the gallbladder to release bile and the pancreas to secrete digestive enzymes.

(C) Secretin is a hormone produced by the $S$-cells of the duodenum in the small intestine.
It is released in response to the presence of acidic chyme (partially digested food mixed with gastric acid) entering the duodenum from the stomach.
The primary function of secretin is to stimulate the pancreas to release bicarbonate-rich fluid,which helps neutralize the acidity of the chyme,creating an optimal $pH$ for the activity of pancreatic enzymes.

(D) The secretion of intestinal juice (succus entericus) is regulated by two main hormones:
$1$. $Enterocrinin$: This hormone stimulates the crypts of Lieberkühn to secrete intestinal juice.
$2$. $Duocrinin$: This hormone stimulates the Brunner's glands to secrete mucus and enzymes into the intestinal juice.
Therefore,both $Enterocrinin$ and $Duocrinin$ are involved in the regulation of intestinal juice secretion.

(A) Omnivores consume a wide variety of food sources,including both plant and animal matter. Because they need to digest diverse types of complex macromolecules such as cellulose,starch,proteins,and fats,they require a broader and more concentrated array of digestive enzymes compared to herbivores (which primarily digest plant matter) or carnivores (which primarily digest animal proteins and fats). Therefore,omnivores possess the highest concentration and diversity of digestive enzymes.

(D) Enterokinase (also known as enteropeptidase) is an enzyme secreted by the intestinal mucosa.
Its primary function is to convert the inactive proenzyme $Trypsinogen$ into its active form,$Trypsin$.
This activation is a critical step in the protein digestion process within the small intestine,as $Trypsin$ subsequently activates other pancreatic zymogens like chymotrypsinogen and procarboxypeptidase.

(A) Cholecystokinin $(CCK)$ is a peptide hormone produced by the $I$-cells in the mucosal epithelium of the small intestine (specifically the duodenum and jejunum).
Its primary function is to stimulate the contraction of the gallbladder to release bile into the duodenum.
Additionally,it stimulates the pancreas to release digestive enzymes.
Therefore,option $A$ is the correct description.

(C) Secretin is a peptide hormone produced by the $S$-cells of the duodenum in the gastrointestinal tract.
It is released in response to low $pH$ (acidic chyme) in the duodenum.
Its primary function is to stimulate the exocrine pancreas to secrete water and bicarbonate ions $(HCO_3^-)$ into the duodenum to neutralize the acidic chyme.
Therefore,the correct answer is $C$ (Pancreas).

(B) Lipids are complex molecules that require specific enzymes for their breakdown into simpler components like fatty acids and glycerol. The enzyme $Lipase$ is specifically responsible for the hydrolysis of lipids (fats) into fatty acids and monoglycerides. Sucrase breaks down sucrose,protease breaks down proteins,and ligase is involved in joining $DNA$ fragments.

(B) Sucrose is a disaccharide composed of glucose and fructose.
In the human digestive system,the enzyme responsible for the hydrolysis of sucrose into its constituent monosaccharides (glucose and fructose) is known as invertase (also called sucrase).
Therefore,the correct option is $B$.

(C) The correct answer is $C$.
$1$. Cholecystokinin $(CCK)$ is a hormone secreted by the $I$-cells of the duodenum and jejunum. It stimulates the pancreas to secrete and release digestive enzymes into the pancreatic juice and also causes the contraction of the gall bladder to release bile.
$2$. Secretin is a hormone secreted by the $S$-cells of the duodenum in response to low $pH$ (acidic chyme). It primarily stimulates the pancreatic ducts to secrete a fluid rich in bicarbonate ions $(HCO_3^-)$,which helps neutralize the acidic chyme in the duodenum.

(D) Enterokinase (also known as enteropeptidase) is an enzyme secreted by the intestinal mucosa. Its primary function is to activate trypsinogen into trypsin. Trypsin is a crucial protease that further activates other pancreatic zymogens like chymotrypsinogen and procarboxypeptidase. If enterokinase is not produced,trypsinogen will not be converted into active trypsin. Consequently,the entire cascade of protein digestion in the small intestine will be severely impaired,leading to incomplete protein digestion.

(B) In humans,the digestion of milk protein (casein) begins in the stomach. The enzyme $Rennin$ (also known as $Chymosin$) is a proteolytic enzyme that is secreted in the stomach of infants. It converts the soluble milk protein $Casein$ into insoluble $Paracasein$ (calcium paracaseinate),which is then further digested by $Pepsin$. While $Rennin$ is highly active in infants,its production decreases significantly in adults. Therefore,$Rennin$ is responsible for the initial step of milk protein digestion.

(A) Chymotrypsin is a digestive enzyme that belongs to the class of serine proteases.
It is secreted by the pancreas in an inactive form called chymotrypsinogen.
In the small intestine,it is activated by trypsin and functions to break down proteins into smaller peptides by hydrolyzing peptide bonds.
Therefore,it is classified as a proteolytic enzyme.

(B) In infant mammals,the stomach secretes a proteolytic enzyme called $Rennin$ (also known as $Chymosin$).
This enzyme is specifically responsible for the digestion of milk proteins,primarily $Casein$.
$Rennin$ converts the soluble milk protein $Casein$ into insoluble $Paracasein$ (calcium paracaseinate),which allows the milk to remain in the stomach for a longer duration for further digestion by $Pepsin$.
Therefore,$Rennin$ plays a crucial role in milk digestion in infants.