Starch to Sugar
Corn digests to sugar
To discuss carbohydrate digestion, let's start with the example of corn starch being broken down into glucose. You can see this process by looking at the diagram to the right (click the image to enlarge).
Inside the corn kernel is starch. Starch is represented by the blue hexagonal shapes linked together. Remember, starch is essentially glucose (sugar) linked together. Starch digestion starts in the mouth with the enzyme salivary amylase. The enzyme is like a little hacksaw, chopping off fragments of the large starch molecule into smaller segments. Very little starch digestion occurs in the stomach, but amylase stays activated until low pH, essentially the acidity of the stomach denatures (inactivates) it. More on this later!
Once the starch fragments leave the stomach, they enter the small intestines. The starch segments, which are essentially glucose chains, are further broken down to maltose and then glucose. Maltose is a disaccharide and a simple carbohydrate (CHO). Glucose is a single sugar unit, or monosaccharide, also known as a simple carbohydrate (CHO).
Inside the corn kernel is starch. Starch is represented by the blue hexagonal shapes linked together. Remember, starch is essentially glucose (sugar) linked together. Starch digestion starts in the mouth with the enzyme salivary amylase. The enzyme is like a little hacksaw, chopping off fragments of the large starch molecule into smaller segments. Very little starch digestion occurs in the stomach, but amylase stays activated until low pH, essentially the acidity of the stomach denatures (inactivates) it. More on this later!
Once the starch fragments leave the stomach, they enter the small intestines. The starch segments, which are essentially glucose chains, are further broken down to maltose and then glucose. Maltose is a disaccharide and a simple carbohydrate (CHO). Glucose is a single sugar unit, or monosaccharide, also known as a simple carbohydrate (CHO).
Let's take a look at the various types of carbohydrates and how they are digested. Looking at the diagram below:
Let's start with the image on the left, a piece of candy. Candy is mostly made up of sucrose. Sucrose breaks down to glucose and fructose. Next, look at the center diagram. Milk breaks down to lactose which then breaks down to glucose and galactose. Lastly, on the far right we have a bagel. Just like the corn discussed above, the carbohydrates in a bagel are mostly starch. Remember, starch is a chain of glucose, strung together and then stacked and branched. Starch breaks down to shorter glucose chains. This process starts in the mouth with salivary amylase. The process slows in the stomach and then goes into overdrive in the small intestines. The short glucose chains are broken down to maltose and then to glucose.
Carbohydrate Digestion and Absorption Video
References
- Groff. J, Gropper S. Chapter 4 Carbohydrates. In: Advanced Nutrition and Human Metabolism 3rd ed. Belmont, CA. Wadsworth; 2000.
- Sizer FS. Whitney E. Chapter 4 Carbohydrates. In: Nutrition Concepts and Controversies 13th ed. Belmont, CA. Wadsworth; 2014.
- Candy, milk and bagel digestion by Christine Dobrowolski using milk by Hector Gomez, bagel modified from johnny_automatic and candy by pitr on OpenClipArt, CC0 1.0
- Corn to glucose diagram by Christine Dobrowolski using corn by gnokii on OpenClipArt, CC0 1.0.
Last updated April 8, 2016