Digestion and also Absorption of Carbohydrates

Imagine taking a bite the pizza. It tastes amazing, but it"s additionally full the fuel for her body, much of it in the kind of carbohydrates.

You are watching: Breaks disaccharide into glucose and galactose

What varieties of carbohydrates would certainly you find in the bite?

Lactose from the cheese

Sucrose, glucose, and fructose indigenous the naturally-occurring sugars in the tomatoes, and also sugar the may have been included 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 carbohydrate in her body, you very first need come digest them. Last week, us explored the gastrointestinal system and the basic procedure of digestion. Now that friend know around the different varieties of carbohydrates, we"ll take it a closer watch at how these molecules are digested together they travel through the GI system.

In the image below, monitor the number to view what wake up to carbohydrates at each site of digestion.


Fig. 4.1. The digestive system

1 - Mouth or oral Cavity

As you chew your bite of pizza, you"re utilizing mechanical cradle to begin to break it right into smaller pieces and mix it v saliva, created by numerous salivary glands in the oral cavity.

Some enzymatic cradle of starch occurs in the mouth, due to the action of the enzyme outstanding amylase. This enzyme beginning to break the lengthy glucose chains of strength into much shorter chains, part as tiny as maltose. (The various other carbohydrates in the bread don"t undergo any kind of enzymatic digestion in the mouth.)


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

2 - Stomach

The short pH in the stomach inactivates outstanding amylase, so it no much longer works when it arrives at the stomach. Back there"s much more mechanical digestion in the stomach, there"s little chemical cradle of carbohydrates here.

3 - small intestine

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


Fig. 4.3. The enzyme pancreatic amylase breaks starch right into smaller polysaccharides and maltose.

The remainder of the work of carbohydrate cradle is excellent by enzymes created by the enterocytes, the cells lining the tiny intestine. When it comes to digesting your slice of pizza, this enzymes will malfunction the maltase developed in the procedure of strength digestion, the lactose native the cheese, and also the sucrose present in the sauce.

Maltose is spend by maltase, developing 2 glucose molecules


Lactose is digested by lactase, creating glucose and also galactose


Sucrose is spend by sucrase, creating glucose and also fructose


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

(Recall that if a person is lactose intolerant, lock don"t make enough lactase enzyme to digest lactose adequately. Therefore, lactose passes to the huge intestine. There it draws water in through osmosis and also is fermented by bacteria, causing symptoms such as flatulence, bloating, and diarrhea.)

By the finish of this procedure of enzymatic digestion, we"re left with 3 monosaccharides: glucose, fructose, and also galactose. These can now be soaked up across the enterocytes that the small intestine and into the bloodstream to it is in transported to the liver.

Digestion and also absorption of carbohydrates in the tiny intestine are depicted in a an extremely simplified schematic below. (Remember the the inner wall of the little intestine is actually written of huge circular folds, inside wall with numerous villi, the surface ar of i beg your pardon are comprised of microvilli. Every one of this gives the tiny intestine a substantial surface area for absorption.)


Fig. 4.5. Digestion and also absorption of carbohydrate in the tiny intestine.

Fructose and galactose space converted to glucose in the liver. Once soaked up carbohydrates pass with the liver, glucose is the main kind of carbohydrate turn around in the bloodstream.

4 - large Intestine or Colon

Any carbohydrates that weren"t spend in the small intestine -- mostly fiber -- pass into the huge intestine, but there"s no enzymatic cradle of these carbohydrates here. Instead, bacteria life in the big intestine, sometimes called our gut microbiota, ferment these carbohydrates to feeding themselves. Fermentation causes gas production, and also that"s why we might experience bloating and also flatulence ~ a particularly fibrous meal. Fermentation likewise produces short-chain fat acids, which our large intestine cells have the right to use as an power source. End the last decade or so, an ext and much more research has displayed that our gut microbiota are incredibly important to ours health, playing important roles in the duty of our immune response, nutrition, and risk of disease. A diet high in totality food resources of fiber help to preserve a populace of healthy gut microbes.

Summary of Carbohydrate Digestion:

The main goal the carbohydrate digestion is to rest polysaccharides and also disaccharides into monosaccharides, which can be took in into the bloodstream.

1. After ~ eating, nothing requirements to occur in the digestive street to the monosaccharides in a food favor grapes, because they are already little enough come be absorbed as is.

2. Disaccharides in the grape or in a food prefer milk are broken down (enzymatically digested) in the digestive street to monosaccharides (glucose, galactose, and also fructose).

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

4. Fiber in food is no enzymatically spend in the cradle tract, because humans don"t have enzymes to carry out this. However, part dietary fiber is fermented in the big intestine through gut microbes.

Table 4.1. An overview of Enzymatic digestion of Carbohydrate

Macronutrients in Food

Is this Macronutrient Enzymatically Digested?

(enzyme name)

What Is soaked up Into the Villi ~ Digestion?







Fructose. The is then transported come the liver wherein it is converted to glucose.

See more: Food Brand That Starts With N Analytics Applications In Industry



Galactose. That is then transported come 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 the digestive enzyme to breakdown fiber, however some is fermented by gut microbes in the big intestine.)


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

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