Biochem- Digestion Flashcards
Describe digestion of carbohydrates.
— Salivary amylase hydrolyzes the a-1,4 glycosidic linkage of Polysaccharides into mono and disaccharides.
— These simple sugars and then further broken down (digestion) into the small intestine where the enzyme will hydrolyze the a-1,4 glycosidic linkage.
— entry into content into the duodenum stimulates the release of secretin and cholecystokinin.
Pancreatic amylase digests the polysaccharide sugars into maltose, isomaltose and limit dextrin.
The disaccharides Maltase, lactase and sucrase are digested by maltose, lactose and sucrose respectively into their respective monosaccharide units.
State the functions of secretin and cholecystokinin.
Secretin stimulates the pancreas to release bicarbonate and water which neutralizes the acidic chyme in the stomach
Cholecystokinin stimulates the production of digestive enzymes such as pancreatic amylase.
Describe the absorption of monosaccharides.
Galactose and glucose are absorbed rapidly by the active process.
Fructose and mannose are absorbed by the Na+ independent facilitative transport mechanism.
Describe the digestion of proteins in the stomach.
— Protein digestion begins in the stomach. The digestion of proteins activates the secretion of Gastrin.
— Gastrin activates the secretion of gastric juice which contains HCl and pepsinogen.
— The HCL unfold the protein and activates pepsin.
— Pepsin digest the the protein polypeptides into tripeptides, dipeptides and amino acids.
— Pepsin hydrolyzes the peptide bonds of protein involving aromatic and acidic amino acids.
Describe the digestion of proteins in the Intestine.
Once the components from the stomach enter the small intestines, it activates the production of secretin and cholecystokinin.
Secretin stimulates the release of bicarbonate and pancreatic juice in the pancreas whereas cholecystokinin stimulates the secretion of pancreatic endo and exopeptidases.
Endopeptidases cleaves the internal peptide bonds of proteins into smaller ones.
Trypsin - hydrolyzes bonds contributed by lysine and arginine
Chymotrypsin - hydrolyzes phones involving carboxyl group amino acids
Elastase- hydrolyzes bonds formed by alanine, serine and glycine
What is the function of the endopeptidases trypsin, chymotrypsin and elastase in the digestion of proteins in the intestine?
Trypsin hydrolyzes the peptide bond of proteins whose caboxyl group is contributed to lysine and arginine.
Chymotrypsin hydrolyzes the peptide bond of proteins who has the carboxyl group aromatic amino acid.
Elastase hydrolyzes the peptide bonds formed by non polar amino groups.
What is the function of the exopeptidases, carboxylpeptidase and aminopeptidase?
They hydrolyze the first peptide group from the free carboxyl and amino terminal end, respectively.
Describe the absorption of proteins (amino acids)
Amino acids are absorbed in the Na+ dependent active transport mechanism, which requires ATP as a source of energy.
Describe the absorption of Lipids.
Digestion of lipids is determined by bile salts (emulsification) and does not begin in the stomach.
The short and medium end of the chain fatty acids are absorbed via the mucosal chains and enter the portal vein.
The large fatty acid chain enters the duodenum where the activates the secretion of secretin and cholecystokinin, which plays there respective roles.
Bile enters the duodenum and emulsifies the lipids. After emulsification, lipase, phospholipase A2 and cholesterol esterase hydrolyzes the lipids.
Describe the role of secretin and cholecystokinin in the digestion of lipids.
Cholecystokinin:
Stimulates the production and release of the digestive enzymes, lipase
Helps with the contraction of the gall bladder to release the bile salts in the intestine.
Decrease gastric motility, which decreases the release of gastric contents into the SI.
Secretin- stimulates the release of a bicarbonate solution that neutralizes the acidic chyme of the stomach and changes it to alkaline pH.
Why is the formation of alkaline pH important in the digestion of lipids?
For the proper action of lipase and intestinal enzymes.
What happens to the medium fatty acid chains in digestion?
They are absorbed into the mucosal cells and resynthesized in the form of chylomicron to be sent in the blood via the lymph vessels.
What happens to tryglycerides for it to be utilized in the body?
It is hydrolyzes by lipase to release glycerol and fatty acids.
The fatty acid is then converted to CO2 and H2O by a large energy source and the glycerol goes through glycolysis or gluconeogenesis.
List the vitamins and minerals of the intestines.
Duodenum: Fe, Ca, Mg, Zn
Ileum- Fat soluble vitamins and B12
Jejunum- Vit C, B1-B6, Folic acid
Colon- Na+, K+ and Vit K.
