Name: carbohydrate breakdown in the digestive tract
Uploaded: 2026-08-26T08:19:53.394Z
Duration: 1 min 14 s
Channel: JoVE

K12 Standards

Alabama Course of Study Science

9-12

Human Anatomy and Physiology

from-molecules-to-organisms-structures-and-processes

From Molecules to Organisms: Structures and Processes

9-12.HA.1.10

Carbohydrate Digestion

Foods such as cereals, tubers, fruits, and milk contain carbohydrates mainly as starch, lactose, and sucrose.Carbohydrate digestion begins in the mouth, where chewing mixes food with saliva. Here, salivary amylase starts breaking large starch molecules into smaller sugar chains.When food reaches the stomach, carbohydrate digestion pauses because the acidic environment of the stomach inactivates salivary amylase.As food enters the small intestine, pancreatic amylase continues breaking down the remaining starch into smaller sugars.Enzymes on the surface of the intestinal microvilli then split these sugars into single sugar units.For example, sucrase splits sucrose into glucose and fructose, while lactase splits lactose into glucose and galactose.These simple sugars are transported across the intestinal epithelium into the bloodstream and are taken up by body cells as a main source of energy.

carbohydrate digestion

Carbohydrate digestion and metabolism break down simple and complex carbohydrates from food into saccharides (i.e., sugars) for the body to use as energy. Carbohydrate digestion starts in the mouth during mastication, or chewing. The masticated carbohydrates remain intact in the stomach. Digestion resumes in the duodenum of the small intestine, where pancreatic alpha-amylase and brush border enzymes of the microvilli convert complex carbohydrates to monosaccharides. Finally, the monosaccharides are absorbed by the intestinal epithelium for energy usage.

<h4>Types of Carbohydrates</h4>

Three basic types of carbohydrates are found in the human diet: simple carbohydrates, complex carbohydrates, and fiber. Simple carbohydrates are monosaccharide molecules such as glucose, fructose, and galactose. Complex carbohydrates, on the other hand, are polysaccharides composed of long chains of glucose. Finally, fiber is a carbohydrate that is found in the cellulose of plant-based foods. It cannot be broken down by the body for energy, but it does play a vital role in healthy digestion by helping ingested food to move along the digestive system.

Carbohydrate digestion and metabolism break down simple and complex carbohydrates from food into saccharides (i.e., sugars) for the body to use as energy. ...

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Biology

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Nutrition and Digestion

KEY TERMS AND CONCEPTS

carbohydrate breakdown in the digestive tract

Carbohydrate digestion breaks food carbohydrates into saccharides, or sugars, that the body can use for energy. It begins in the mouth during mastication, which means chewing. The masticated carbohydrates then pass through the stomach without being broken down further.

Digestion starts again in the duodenum, the first part of the small intestine. There, pancreatic alpha-amylase and brush border enzymes on the microvilli help convert complex carbohydrates into monosaccharides. These simple sugar units are then absorbed by the intestinal epithelium for energy use.

The human diet includes three basic types of carbohydrates: simple carbohydrates, complex carbohydrates, and fiber. Simple carbohydrates are monosaccharides such as glucose, fructose, and galactose. Complex carbohydrates are polysaccharides, which are long chains of glucose. Fiber is found in the cellulose of plant-based foods. The body cannot break fiber down for energy, but it helps healthy digestion by moving food along the digestive system.

Carbohydrate Breakdown in the Digestive Tract

carbohydrate-breakdown-in-the-digestive-tract

overview of human digestion

Saliva, Stomach Acid, and Gut Health

The human digestive system is monogastric, which means the stomach has one chamber for digestion. Several other animals also have monogastric digestive systems, including pigs, horses, dogs, and birds. This chapter focuses on the human digestive system. Saliva is a watery fluid released by the salivary glands into the mouth. It is about 99.5% water and also contains electrolytes, mucus, white blood cells, epithelial cells, enzymes, and antimicrobial agents. The enzymes in saliva begin...

anatomy of the intestines

Small and Large Intestine Functions

The small and large intestines complete digestion and absorb nutrients, water, and electrolytes. They are two structurally distinct organs with different shapes and jobs. Together, they move food material from the stomach toward elimination. The small intestine is about 7 meters long and has an inner diameter of only 2.5 cm. Most nutrient absorption happens here, so its inner lining is highly folded and covered with villi, which are finger-like projections. Each villus contains hundreds of...

accessory organs

Digestive Glands and Enzymes

Digestive glands and accessory organs help break down food even though food does not pass through them. They add enzymes and other fluids to the digestive tract to support digestion. The salivary glands release saliva, a fluid that contains water, mucus, and amylase. Amylase is a digestive enzyme that starts breaking down starches and other carbohydrates before food reaches the stomach. The liver, gallbladder, and pancreas also support digestion. They send their secretions into the duodenum,...

Carbohydrate digestion breaks food carbohydrates into saccharides, or sugars, that the body can use for energy. It begins in the mouth during mastication, which means chewing. The masticated carbohydrates then pass through the stomach without being broken down further. Digestion starts again in the duodenum, the first part of the small intestine. There, pancreatic alpha-amylase and brush border enzymes on the microvilli help convert complex carbohydrates into monosaccharides. These simple...

protein digestion

Protein Breakdown and Amino Acid Use

Protein digestion starts in the stomach, where strong acid helps unfold protein structure and expose peptide bonds in polypeptide chains. Digestive enzymes then begin breaking those chains into smaller pieces that can be processed by the body. Pepsin is a protease, which means it is a protein-digesting enzyme. It is made in the stomach and works with chymotrypsin and trypsin, enzymes released in the small intestine. These enzymes cut specific links between amino acids and form shorter...

lipid digestion

Lipases and Bile in Fat Breakdown

Lipases and bile help the body break down lipids, which are large molecules that do not mix well with water. Because most digestive enzymes are water-based, lipids need special steps before the body can use them. Lingual lipase is an enzyme made by acinar cells in the sublingual gland. It is found in saliva, but it has only a small role in the mouth. Its best pH, or acidity level, is 3.5-6.0, so it becomes active after chewed food reaches the acidic stomach. Gastric lipase is another acidic...

neural regulation

Brain and Gut Control of Digestion

Brain and gut control digestion through a cephalic phase and the enteric nervous system. The cephalic phase begins when the brain sees or smells food. It sends impulses through cranial nerves to the salivary glands and stomach so the body is ready to eat. This first response is a conditioned, or learned, reaction to familiar foods. Appetite also changes the response. People may make more saliva and hear more stomach rumbling when they think about apple pie than broccoli. The hypothalamus and...

hormonal regulation

Digestive Hormones and Stomach Control

Digestive hormones control when the stomach makes acid and when food moves into the small intestine. They work with the neuroendocrine system, which links nerve signals and hormone release during digestion. In the stomach, proteins are detected by sensory neurons in the enteric nervous system. This stimulates the pyloric gland to release gastrin. Gastrin then helps trigger histamine release, and together they start hydrochloric acid production. The acid helps break food down into chyme. As the...

key terms and concepts

Follow how carbohydrates are broken down in the mouth and small intestine, then absorbed as sugars. Learn the roles of simple carbs, complex carbs, and fiber.

Carbohydrate Breakdown in the Digestive Tract | JoVE K12

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HS-LS1-2

Florida Department of Education

SC.912.L.14

SC.912.L.14.46

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New York State Science Learning Standards

Structure and Function

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a. Construct an explanation of the relationships between the integumentary system and other organ systems, including the body's mechanisms for maintaining homeostasis. Examples: Explain how changes in vessel diameter and evaporation of water over the skin contribute to thermoregulation (cardiovascular). Explain how sweat is used to excrete nitrogenous waste from the blood (cardiovascular). Explain how the skin and mucous membranes create a barrier against infection (immune system).

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4. Develop and build a three-dimensional model to illustrate the structures of the muscular system, including muscle locations, origins, and insertions, and explain their roles in movement and support. Example: Design and build a model of a lever to illustrate the relationship between bones and muscles and explain their roles in body movement and support.

9-12.HA.1.4

Microscopic Anatomy of Skeletal Muscles

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The Sarcomere

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Excitation-Contraction Coupling in Skeletal Muscles

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Relaxation of Skeletal Muscles

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a. Model the cellular physiology of skeletal muscle, including how the cell functions in muscle contraction and relaxation. Example: Use straws and paper to create a model of a sarcomere to illustrate how the fibers move during contraction and relaxation.

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b. Obtain, evaluate, and communicate information to explain muscle fatigue and tone in terms of muscle cell physiology.

9-12.HA.1.4.b

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5. Obtain, evaluate, and communicate information explaining the relationship between the structures and functions of the central nervous system and the peripheral nervous system.

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a. Use a model to illustrate the role of action potentials in neural transmission. Clarification: Discussions of sodium-potassium pumps and ion channels are not required.

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Carbohydrate Breakdown in the Digestive Tract

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