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Chemical Digestion of Carbohydrates: Definition & Process

Lesson Transcript
Instructor: Rebecca Gillaspy

Dr. Gillaspy has taught health science at University of Phoenix and Ashford University and has a degree from Palmer College of Chiropractic.

Carbohydrates, including sugars and starches, are organic compounds that serve as a major energy source for your body. Discover the world of carbohydrates and learn about the building blocks of carbohydrates (monosaccharides) that join to form disaccharides (sugars), polysaccharides (starches and fiber), and how the digestive tract breaks down carbohydrates via hydrolysis. Updated: 08/26/2021


The calories that you consume during the day basically consist of a combination of three main nutrients, called carbohydrates, proteins and fats. When you sit down to a meal, you probably do not give much thought to what happens to these nutrients as they make their way through your digestive tract. But when we take a closer look, we see that each of these nutrients is made up of long chains of subunits that must be chemically broken down by enzymes.

Nutrients are made up of long chains of subunits that must be broken down by enzymes

These nutrients must be broken down so they are small enough to be absorbed out of your digestive tract, otherwise they would pass right through you, and you would suffer from malnutrition. This lesson will focus on carbohydrates. Carbohydrates are organic compounds, including sugars and starches, that serve as a major energy source for your body. In this lesson, you will learn how the carbohydrates that you eat are broken down in your digestive tract.

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  • 0:05 Digestion
  • 0:58 Monosaccharides
  • 1:49 Disaccharides and…
  • 3:05 Hydrolysis
  • 4:15 Lesson Summary
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The basic building blocks of any carbohydrate, whether it is bread, a baked potato or a plate of pasta, are called monosaccharides. Monosaccharides are defined as simple sugars because they are in their simplest form and cannot be broken down more than they already are. In fact, their name is very descriptive. We see that the prefix 'mono' means one, and the suffix 'saccharide' means sugar. So, a monosaccharide is literally 'one sugar,' standing by itself, with no other units attached to it.

Monosaccharides are the basic building blocks of carbohydrates

There are three common monosaccharides in your diet. They are called glucose, fructose and galactose. Of these three, glucose is the most important, and when we talk about blood sugar levels, we are referring to glucose. Glucose is also a major energy source for your body cells.

Disaccharides and Polysaccharides

When you join a couple of monosaccharides together you form a disaccharide. The prefix 'di' means two, and disaccharides are defined as a class of sugars that are composed of two monosaccharides, basically a 'double sugar.' There are three common disaccharides in your diet, and we call them sucrose, lactose and maltose.

There is one more type of carbohydrate that your digestive system is able to digest and break down into a monosaccharide, and that is starch. Starch is a polysaccharide. The prefix 'poly' means many, and polysaccharides are defined as a class of sugars that are composed of many monosaccharides.

There is another type of polysaccharide that you eat called cellulose. Cellulose is found in foods, such as fruits, vegetables and grains, but your body does not have the enzymes that it needs to break down cellulose. Therefore, we do not get nutrients from cellulose, but these foods do provide us with fiber. Fiber cannot be digested but helps the body move food through the digestive tract. Fiber is almost like a scrub brush that moves through your intestine and keeps food remnants moving along their path.

Cellulose provides us with fiber, which cannot be digested but helps food move through the digestive tract

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