Digestion and Absorption that Carbohydrates

Imagine taking a bite of pizza. It tastes amazing, however it"s also full that fuel for her body, much of the in the type of carbohydrates.

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What species of carbohydrates would certainly you discover in that bite?

Lactose from the cheese

Sucrose, glucose, and also fructose native the naturally-occurring sugars in the tomatoes, as well as sugar that may have been added to the sauce

Starch in the flour used to do the crust

Fiber in the flour, tomatoes, and basil.

In order to use these food carbohydrates in your body, you first need come digest them. Last week, we explored the cradle system and the basic procedure of digestion. Currently that friend know around the different species of carbohydrates, we"ll take a closer watch at just how these molecules are digested as they travel with the GI system.

In the picture below, monitor the number to see what wake up to carbohydrate at each website of digestion.


Fig. 4.1. The cradle system

1 - Mouth or dental Cavity

As girlfriend chew your bite the pizza, you"re making use of mechanical cradle to start to rest it right into smaller pieces and mix it through saliva, created by number of salivary glands in the dental cavity.

Some enzymatic digestion of starch wake up in the mouth, due to the action of the enzyme outstanding amylase. This enzyme starts to rest the lengthy glucose chain of starch into much shorter chains, part as small as maltose. (The various other carbohydrates in the bread don"t undergo any enzymatic cradle in the mouth.)


Fig. 4.2. The enzyme outstanding amylase division starch into smaller polysaccharides and also maltose.

2 - Stomach

The short pH in the stomach inactivates outstanding amylase, so that no longer works once it arrives at the stomach. Return there"s an ext mechanical cradle in the stomach, there"s tiny chemical cradle of carbohydrates here.

3 - small intestine

Most carbohydrate digestion wake up in the tiny intestine, thanks to a suite that enzymes. Pancreatic amylase is secreted from the pancreas into the little intestine, and like outstanding amylase, it division starch down to little oligosaccharides (containing 3 to 10 glucose molecules) and maltose.


Fig. 4.3. The enzyme pancreatic amylase division starch into smaller polysaccharides and also maltose.

The rest of the work of carbohydrate cradle is done by enzymes created by the enterocytes, the cell lining the little intestine. Once it concerns digesting your part of pizza, these enzymes will break down the maltase developed in the process of strength digestion, the lactose indigenous the cheese, and also the sucrose present in the sauce.

Maltose is spend by maltase, creating 2 glucose molecules


Lactose is digested by lactase, creating glucose and galactose


Sucrose is spend by sucrase, forming glucose and also fructose


Fig. 4.4. Activity of the enzymes maltase, lactase, and also sucrase.

(Recall that if a human being is lactose intolerant, they don"t make enough lactase enzyme to digest lactose adequately. Therefore, lactose passes to the big intestine. Over there it color etc water in through osmosis and also is fermented by bacteria, causing symptoms such as flatulence, bloating, and diarrhea.)

By the end of this process of enzymatic digestion, we"re left with three monosaccharides: glucose, fructose, and galactose. These deserve to now be took in across the enterocytes the the little intestine and also into the bloodstream to be transported to the liver.

Digestion and absorption of carbohydrates in the little intestine are shown in a very simplified schematic below. (Remember the the inner wall of the small intestine is actually written of large circular folds, inside wall with countless villi, the surface of i beg your pardon are consisted of of microvilli. Every one of this offers the little intestine a substantial surface area because that absorption.)


Fig. 4.5. Digestion and also absorption of carbohydrates in the little intestine.

Fructose and galactose room converted to glucose in the liver. Once took in carbohydrates pass with the liver, glucose is the main kind of carbohydrate circulating in the bloodstream.

4 - huge Intestine or Colon

Any carbohydrates that weren"t digested in the tiny intestine -- greatly fiber -- pass right into the large intestine, yet there"s no enzymatic digestion of these carbohydrates here. Instead, bacteria living in the huge intestine, sometimes dubbed our gut microbiota, ferment this carbohydrates to feed themselves. Fermentation reasons gas production, and that"s why we might experience bloating and flatulence after ~ a particularly fibrous meal. Fermentation likewise produces short-chain fat acids, which our large intestine cells deserve to use together an energy source. End the last decade or so, much more and more research has presented that our gut microbiota room incredibly crucial to our health, playing necessary roles in the function of our immune response, nutrition, and risk of disease. A diet high in totality food sources of fiber help to maintain a populace of healthy gut microbes.

Summary of Carbohydrate Digestion:

The main goal of carbohydrate cradle is to rest polysaccharides and disaccharides into monosaccharides, which have the right to be absorbed into the bloodstream.

1. After ~ eating, nothing requirements to occur in the digestive tract to the monosaccharides in a food like grapes, because they space already small enough come be absorbed as is.

2. Disaccharides in that grape or in a food choose milk are damaged down (enzymatically digested) in the digestive tract to monosaccharides (glucose, galactose, and also fructose).

3. Starch in food is damaged down (enzymatically digested) in the digestive street to glucose molecules.

4. Fiber in food is no enzymatically spend in the cradle tract, due to the fact that humans don"t have actually enzymes to do this. However, part dietary fiber is fermented in the huge intestine through gut microbes.

Table 4.1. Review of Enzymatic cradle of Carbohydrate

Macronutrients in Food

Is this Macronutrient Enzymatically Digested?

(enzyme name)

What Is soaked up Into the Villi ~ Digestion?







Fructose. That is then transported to the liver wherein it is convert to glucose.

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Galactose. The is climate transported to the liver whereby it is convert to glucose.



Yes (maltase)



Yes (sucrase)

Glucose, Fructose


Yes (lactase)

Glucose, Galactose




(amylase, maltase)



No (Humans don"t have actually the digestive enzymes to failure fiber, however some is fermented by gut microbes in the big intestine.)


This video clip reviews the procedure of carbohydrate digestion: https://www.wiley.com/college/grosvenor/0470197587/animations/dig3a/

This video clip will help you recognize carbohydrates in foods, what carbohydrates should be enzymatically digested, and also what is absorbed: https://youtu.be/XcIInk32nn4