Digestion of Carbohydrates (Nursing)

00:01 So let's take a closer look at the digestion of certain biomolecules starting with carbohydrates.

00:09 Only monosaccharides are able to be absorbed by the small intestine.

00:14 Staarch and as well and disaccharides are broken down into oligosaccharides and disaccharides.

00:22 This process actually begins at ingestion in the mouth with the salivary amylase has that are secreted by those salivary glands.

00:33 They are further broken down into lactose, maltose and sucrose and then finally into the monosaccharides, glucose, fructose and galactose mostly at the duodenum of the small intestine.

00:50 So let's look at the steps of starch digestion in the intestine.

00:55 Recall that the pancreas is going to secrete pancreatic amylase into the duodenum.

01:02 The pancreatic amylase is going to break down starch or glycogen that has escaped the salivary amylase that was in the mouth.

01:11 These are going to be broken down into oligosaccharides and disaccharides.

01:17 Further, brush border enzymes that are released by the cells of the microvilli in the mucosa of the small intestines, are going to then further break these down into monosaccharides.

01:31 The brush border enzymes include dextrinase, lactase, glucoamylase, maltase and sucrase which is going to break these down into lactose, maltose and sucrose and then into glucose, fructose and galactose.

01:48 Now that they're in their monosaccharide form, they're able to be co-transported across the apical membrane of our absorptive epithelial cells in the small intestine.

01:59 Mostly by secondary active transport with sodium ions.

02:05 On the other side of these cells they're going to exit across the basolateral membrane by way of facilitated diffusion into the blood.

02:18 So to recap with a diagram, the starches or carbohydrates will be broken down by pancreatic amylases.

02:28 They are further broken down by the brush border enzymes of the microvilli.

02:34 And from there, they are transported across the apical membrane by active transport with sodium ions.

02:42 Once they cross through the cell they exit the bilateral membrane by facilitated diffusion and then are able to enter into the bloodstream.

02:55 So to summarize, amylase from the mouth and the pancreas begin to break down our carbohydrates in the mouth and the small intestines.

03:05 The remaining oligosaccharides and disaccharides are further broken down by brush border enzymes in the microvilli of the small intestines to form the monosaccharides.

03:17 These can then be absorbed by the absorptive epithelial cells of the small intestine.

03:23 After absorption into the blood the monosaccharides will be taken to the liver by way of the hepatic portal vein.