NUTR 3210 Lecture Notes - Lecture 5: Maltase, Bloating, Facilitated Diffusion

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Unit 05
Carbohydrates
Video
Carbohydrate Digestion & Absorption
Transcript
Slide 1
In this video, we will go through an overview of carbohydrate digestion and
absorption.
Slide 2
Let’s start our discussion with an overview of how carbohydrate digestion occurs
in different regions of the gastrointestinal tract. Recall from unit 02 that digestion
is the process of breaking down food by both mechanical and enzymatic action
into substances that can be absorbed into the body. For carbohydrates, as for all
nutrients, digestion will begin in the mouth, where we have mechanical
breakdown of food through chewing, as well as lubrication and mixing with saliva.
As well, there is some enzymatic digestion of carbohydrates in the mouth; saliva
secreted by the salivary glands contains an enzyme called alpha amylase, which
can hydrolyze the alpha 1,4 glycosidic bonds found in molecules such as
amylose, and amylopectin. The digestion of carbohydrates in the mouth doesn’t
actually accomplish a lot of breakdown, but it is thought to allow for nutrient
sensing, thereby preparing the body for carbohydrate breakdown. If we continue
to move down the esophagus into the stomach, while there may be some initial
continuation of digestion from salivary alpha amylase, this doesn’t last long, since
the enzyme will be denatured by stomach acid. Stomach acid can liberate
carbohydrates from the food matrix but there really isn’t any more actual
digestion that occurs. The pancreas secretes another type of amylase enzyme,
called pancreatic amylase, that is very much like the salivary amylase and acts to
break down alpha 1,4 glycosidic bonds. The pancreas secretes this enzyme into
the small intestine through the pancreatic duct. In the small intestine, pancreatic
amylase will act to breakdown alpha 1,4 bonds, while the brush border enzymes
continue breakdown of carbohydrate molecules until the end products are all
monosaccharides, except, of course, for the fibre, which is indigestible here.
Absorption of the mononosaccharides occurs in the small intestine, and we will
explore this in more detail later. The undigested fibre passes into the large
intestine where it can undergo fermentation by colonic bacteria, and produce
volatile fatty acids that can be absorbed and used for energy. The red line
illustrates the enteric nervous system, which regulates the motility, contraction,
and secretions of the gastrointestinal tract.
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Document Summary

In this video, we will go through an overview of carbohydrate digestion and absorption. Let"s start our discussion with an overview of how carbohydrate digestion occurs in different regions of the gastrointestinal tract. Recall from unit 02 that digestion is the process of breaking down food by both mechanical and enzymatic action into substances that can be absorbed into the body. For carbohydrates, as for all nutrients, digestion will begin in the mouth, where we have mechanical breakdown of food through chewing, as well as lubrication and mixing with saliva. The digestion of carbohydrates in the mouth doesn"t actually accomplish a lot of breakdown, but it is thought to allow for nutrient sensing, thereby preparing the body for carbohydrate breakdown. If we continue to move down the esophagus into the stomach, while there may be some initial continuation of digestion from salivary alpha amylase, this doesn"t last long, since the enzyme will be denatured by stomach acid.

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