Gastro intestinal hormones/Digestive enzymes Questions in English

(C) $Cholecystokinin$ $(CCK)$ is a peptide hormone of the gastrointestinal system responsible for stimulating the digestion of fat and protein.
$CCK$ is synthesized by $I$-cells in the mucosal epithelium of the small intestine and secreted in the duodenum.
It stimulates the pancreas to release digestive enzymes and the gall bladder to release bile.
Therefore,it acts on both the pancreas and the gall bladder.

(C) Secretin is a hormone produced by the $S$-cells of the duodenum. It acts on the exocrine pancreas to stimulate the secretion of water and bicarbonate ions into the pancreatic juice,which helps in neutralizing the acidic chyme entering the small intestine from the stomach.

(A) $CCK$ (Cholecystokinin) is secreted by the duodenal mucosa.
It stimulates the secretion of pancreatic enzymes and the contraction of the gall bladder.

(A) Gastrin is a peptide hormone primarily secreted by $G$-cells located in the pyloric antrum of the stomach.
When food enters the stomach,the presence of peptides and amino acids,along with stomach distension,triggers the release of Gastrin into the bloodstream.
Gastrin then travels to the gastric glands and stimulates the parietal cells to secrete hydrochloric acid $(HCl)$ and the chief cells to secrete pepsinogen.
This process is essential for the initiation of protein digestion in the stomach.

(N/A) Trypsinogen is an inactive precursor (zymogen) secreted by the pancreas.
It is converted into its active form,Trypsin,by the enzyme Enterokinase.
Enterokinase is secreted by the intestinal mucosa (specifically the brush border cells of the small intestine).
This activation is a crucial step in protein digestion,as active Trypsin then activates other pancreatic enzymes like chymotrypsinogen and procarboxypeptidase.

(C) The breakdown of nucleotides into sugars and bases occurs in two steps.
First,$Nucleotidase$ breaks down nucleotides into nucleosides and inorganic phosphate.
Second,$Nucleosidase$ breaks down nucleosides into sugars and nitrogenous bases.
Therefore,both enzymes are involved in the complete breakdown process.

(B) The process of digestion in the $GI$ Tract is regulated by both neural and hormonal mechanisms.
Endocrine cells are present in different parts of the Gastrointestinal Tract ($GI$ Tract).
These cells secrete four major peptide hormones: gastrin,secretin,cholecystokinin $(CCK)$,and gastric inhibitory peptide $(GIP)$.
These hormones regulate the secretion of digestive juices and the motility of the digestive tract.

(B) $CCK$ stands for Cholecystokinin.
It is a gastrointestinal hormone secreted by the mucosa of the duodenum.
$CCK$ acts on the pancreas to stimulate the secretion of pancreatic enzymes.
It also acts on the gall bladder to stimulate the contraction of the gall bladder,which leads to the release of bile juice into the duodenum.

(B) $Carboxypeptidase$ is a proteolytic enzyme (protease) that acts on the carboxyl-terminal end of a protein or peptide chain. It cleaves the peptide bond at the $C$-terminus,releasing the terminal amino acid. Therefore,it is an enzyme involved in protein digestion.

(C) $1$. Pepsinogen is an inactive proenzyme secreted by the stomach,which is activated into active pepsin by $HCl$.
$2$. Trypsinogen is an inactive enzyme secreted by the pancreas,which is activated into active trypsin by the enzyme enterokinase (secreted by the intestinal mucosa).
$3$. Once trypsin is formed,it acts as an autocatalyst and activates other pancreatic zymogens like chymotrypsinogen into chymotrypsin and procarboxypeptidase into carboxypeptidase.
$4$. Therefore,the correct sequence of activators is $HCl$,Enterokinase,Trypsin,Trypsin.

(C) Proteolytic enzymes are those that break down proteins into smaller peptides or amino acids.
$1$. Amylase: Breaks down carbohydrates (not proteolytic).
$2$. Lipase: Breaks down fats (not proteolytic).
$3$. Pepsin: Proteolytic enzyme found in the stomach.
$4$. Trypsin: Proteolytic enzyme found in the small intestine.
$5$. Chymotrypsin: Proteolytic enzyme found in the small intestine.
$6$. Carboxypeptidase: Proteolytic enzyme found in the small intestine.
$7$. Maltase: Breaks down maltose (not proteolytic).
$8$. Erepsin: Proteolytic enzyme (mixture of peptidases) found in the small intestine.
The proteolytic enzymes are Pepsin,Trypsin,Chymotrypsin,Carboxypeptidase,and Erepsin.
Total count = $5$.

(D) The activities of the gastrointestinal tract are under neural and hormonal control for proper coordination of different parts.
$1$. Neural control: The muscular activities of different parts of the alimentary canal can be moderated by neural mechanisms,both local and through the Central Nervous System $(CNS)$.
$2$. Hormonal control: Hormonal control of the secretion of digestive juices is carried out by local hormones produced by the gastric and intestinal mucosa.
Therefore,both the neural and endocrine systems regulate the gastrointestinal tract.

(D) The hormone $CCK$ (Cholecystokinin) 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.

(C) The correct matching is as follows:
$P$. Gastrin: Acts on the gastric glands and stimulates the secretion of $HCl$ and pepsinogen $(P-II)$.
$Q$. Secretin: Acts on the exocrine pancreas and stimulates the secretion of water and bicarbonate ions $(Q-I)$.
$R$. $CCK$ (Cholecystokinin): Acts on both the pancreas and the gallbladder to stimulate the secretion of pancreatic enzymes and bile juice,respectively $(R-IV)$.
$S$. $GIP$ (Gastric Inhibitory Peptide): Inhibits gastric secretion and motility $(S-III)$.
Therefore,the correct sequence is $(P-II), (Q-I), (R-IV), (S-III)$.

(A) The enzyme Maltase acts on Maltose to break it down into two molecules of Glucose.
Option $A$ states that Maltose breaks down into Glucose + Galactose,which is incorrect.
Sucrose is broken down by Sucrase into Glucose and Fructose.
Lactose is broken down by Lactase into Glucose and Galactose.
Dipeptides are broken down by Dipeptidases into Amino acids.
Therefore,the reaction in option $A$ is incorrect.

(D) The endocrine cells present in different parts of the gastrointestinal tract secrete four major peptide hormones: $Gastrin$,$Secretin$,$Cholecystokinin$ $(CCK)$,and $Gastric$ $Inhibitory$ $Peptide$ $(GIP)$.
$Erythropoietin$ is a peptide hormone produced by the juxtaglomerular cells of the kidney,which stimulates the formation of red blood cells $(erythropoiesis)$.
Therefore,$Erythropoietin$ is not a gastrointestinal hormone.

(D) Succus entericus,also known as intestinal juice,is secreted by the glands of the small intestine. It contains a variety of enzymes that complete the process of digestion. These enzymes include $enterokinase$,$maltase$,$sucrase$,$lactase$,$dipeptidase$,and $lipase$. Among the given options,$sucrase$,$maltase$,and $dipeptidase$ are all components of the intestinal juice. Trypsin,pepsin,and chymotrypsin are pancreatic or gastric enzymes,not intestinal.