Bile and pancreatic juice change the pH of the chyme in the small intestine. what change occurs in the pH? can you explain the requirement of changing the pH from the perspective of enzyme requirements?
Bile and pancreatic juice change the pH of the chyme in the small intestine. what change occurs in the pH? can you explain the requirement of changing the pH from the perspective of enzyme requirements?
the stomach is all about acid (it is designed for a normal pH of 1.5-3.0). HCL is excreted into the stomach at a pH of 0.8, that is almost pure acid. The acid; bathes & disinfects the stomach, kills bacteria and parasites, activates pepsin so we can digest proteins, stimulates gastrin and breaks down proteins.
After the stomach churns the bolus and mixes it with gastric juice, the food breaks down even more into a paste called chyme (which is very acidic). Chyme is released into the upper part of the small intestine (duodenum) through the pyloric sphincter. As the chyme enters the duodenum the acidic pH (1.5-3.0) of the chyme triggers the small intestine to secrete mucous. Quick note: The small intestine has a dual role as a digestive organ and a gland. At the same time the intestinal walls are secreting mucous, they are also secreting two hormones into the bloodstream, secretin & cholecystokinin (aka – CCK). Secretin stimulates the pancreas to release bicarbonate and pancreatic juice, and CCK stimulates the gallbladder to release bile.
Chyme results from the mechanical and chemical breakdown of a bolus and consists of partially digested food, water, hydrochloric acid, and various digestive enzymes. Chyme slowly passes through the pyloric sphincter and into the duodenum, where the extraction of nutrientsbegins. Depending on the quantity and contents of the meal, the stomach will digest the food into chyme in anywhere between 40 minutes to a few hours.
With a pH of approximately 2, chyme emerging from the stomach is very acidic. The duodenumsecretes a hormone, cholecystokinin (CCK), which causes the gall bladder to contract, releasing alkaline bile into the duodenum. CCK also causes the release of digestive enzymes from the pancreas. The duodenum is a short section of the small intestine located between the stomach and the rest of the small intestine. The duodenum also produces the hormone secretin to stimulate the pancreatic secretion of large amounts of sodium bicarbonate, which then raises pH of the chyme to 7. The chyme then moves through the jejunum and the ileum, where digestion progresses, and the nonuseful portion continues onward into the large intestine. The duodenum is protected by a thick layer of mucus and the neutralizing actions of the sodium bicarbonate and bile.
At a pH of 7, the enzymes that were present from the stomach are no longer active. This then leads into the further breakdown of the nutrients still present by anaerobic bacteria, which at the same time help to package the remains. These bacteria also help synthesize vitamin B and vitamin K, which will be absorbed along with other nutrients.
The coordinated action of the forementioned hormones results in the secretion of a large volume of the pancreatic juice, which is alkaline and enzyme-rich, into duodenum. The pancreas also receives autonomic innervation. The blood flow into pancreas is regulated by sympathetic nerve fibers, while parasympathetic neurons stimulate the activity of acinar and centroacinar cells.
Pancreatic secretion is an aqueous solution of bicarbonate originating from the duct cells and enzymes originating from the acinar cells. The bicarbonate assists in neutralising the low pH of the chyme coming from the stomach, while the enzymes assist in the breakdown of the proteins, lipids and carbohydrates for further processing and absorption in the intestines.
The pH of a solution can have several effects of the structure and activity of enzymes. For example, pH can have an effect of the state of ionization of acidic or basic amino acids. Acidic amino acids have carboxyl functional groups in their side chains. Basic amino acids have amine functional groups in their side chains. If the state of ionization of amino acids in a protein is altered then the ionic bonds that help to determine the 3-D shape of the protein can be altered. This can lead to altered protein recognition or an enzyme might become inactive.
Changes in pH may not only affect the shape of an enzyme but it may also change the shape or charge properties of the substrate so that either the substrate cannot bind to the active site or it cannot undergo catalysis.
In general enzyme have a pH optimum. However the optimum is not the same for each enzyme.
the stomach is all about acid (it is designed for a normal pH of 1.5-3.0). HCL is excreted into the stomach at a pH of 0.8, that is almost pure acid. The acid; bathes & disinfects the stomach, kills bacteria and parasites, activates pepsin so we can digest proteins, stimulates gastrin and breaks down proteins.
After the stomach churns the bolus and mixes it with gastric juice, the food breaks down even more into a paste called chyme (which is very acidic). Chyme is released into the upper part of the small intestine (duodenum) through the pyloric sphincter. As the chyme enters the duodenum the acidic pH (1.5-3.0) of the chyme triggers the small intestine to secrete mucous. Quick note: The small intestine has a dual role as a digestive organ and a gland. At the same time the intestinal walls are secreting mucous, they are also secreting two hormones into the bloodstream, secretin & cholecystokinin (aka – CCK). Secretin stimulates the pancreas to release bicarbonate and pancreatic juice, and CCK stimulates the gallbladder to release bile.
Chyme results from the mechanical and chemical breakdown of a bolus and consists of partially digested food, water, hydrochloric acid, and various digestive enzymes. Chyme slowly passes through the pyloric sphincter and into the duodenum, where the extraction of nutrientsbegins. Depending on the quantity and contents of the meal, the stomach will digest the food into chyme in anywhere between 40 minutes to a few hours.
With a pH of approximately 2, chyme emerging from the stomach is very acidic. The duodenumsecretes a hormone, cholecystokinin (CCK), which causes the gall bladder to contract, releasing alkaline bile into the duodenum. CCK also causes the release of digestive enzymes from the pancreas. The duodenum is a short section of the small intestine located between the stomach and the rest of the small intestine. The duodenum also produces the hormone secretin to stimulate the pancreatic secretion of large amounts of sodium bicarbonate, which then raises pH of the chyme to 7. The chyme then moves through the jejunum and the ileum, where digestion progresses, and the nonuseful portion continues onward into the large intestine. The duodenum is protected by a thick layer of mucus and the neutralizing actions of the sodium bicarbonate and bile.
At a pH of 7, the enzymes that were present from the stomach are no longer active. This then leads into the further breakdown of the nutrients still present by anaerobic bacteria, which at the same time help to package the remains. These bacteria also help synthesize vitamin B and vitamin K, which will be absorbed along with other nutrients.
The coordinated action of the forementioned hormones results in the secretion of a large volume of the pancreatic juice, which is alkaline and enzyme-rich, into duodenum. The pancreas also receives autonomic innervation. The blood flow into pancreas is regulated by sympathetic nerve fibers, while parasympathetic neurons stimulate the activity of acinar and centroacinar cells.
Pancreatic secretion is an aqueous solution of bicarbonate originating from the duct cells and enzymes originating from the acinar cells. The bicarbonate assists in neutralising the low pH of the chyme coming from the stomach, while the enzymes assist in the breakdown of the proteins, lipids and carbohydrates for further processing and absorption in the intestines.
The pH of a solution can have several effects of the structure and activity of enzymes. For example, pH can have an effect of the state of ionization of acidic or basic amino acids. Acidic amino acids have carboxyl functional groups in their side chains. Basic amino acids have amine functional groups in their side chains. If the state of ionization of amino acids in a protein is altered then the ionic bonds that help to determine the 3-D shape of the protein can be altered. This can lead to altered protein recognition or an enzyme might become inactive.
Changes in pH may not only affect the shape of an enzyme but it may also change the shape or charge properties of the substrate so that either the substrate cannot bind to the active site or it cannot undergo catalysis.
In general enzyme have a pH optimum. However the optimum is not the same for each enzyme.
