Carbohydrate Digestion And Absorption - Carbohydrate Metabolism

Summary

In this video, Bryan explains how our bodies digest and absorb carbohydrates, from the moment food enters the mouth to its absorption in the small intestine. He describes the three main types of carbohydrates—monosaccharides, disaccharides, and polysaccharides—and how enzymes like salivary amylase, pancreatic amylase, sucrase, lactase, and maltase break down these molecules into simpler sugars like glucose, fructose, and galactose. Bryan also discusses how these sugars are absorbed into the bloodstream, transported to the liver, and used for energy or stored as glycogen and fat. It's a detailed yet straightforward look at carbohydrate digestion and absorption.

Takeaways

• 😀 Carbohydrates are broken down into three main types: monosaccharides, disaccharides, and polysaccharides.
• 😀 The body uses enzymes to break down larger carbohydrate molecules into smaller units for digestion and absorption.
• 😀 Carbohydrate digestion begins in the mouth with salivary amylase, which breaks down starch molecules.
• 😀 The low pH in the stomach inactivates the salivary amylase, so digestion of carbohydrates is minimal in the stomach.
• 😀 The pancreas releases pancreatic juice in the small intestine, which contains pancreatic amylase to continue starch digestion.
• 😀 Microvilli (brush border) in the small intestine contain enzymes that complete the breakdown of starch into glucose.
• 😀 Disaccharides such as sucrose, lactose, and maltose are broken down by enzymes like sucrase, lactase, and maltase in the small intestine.
• 😀 Glucose, fructose, and galactose are the main products of carbohydrate digestion that are absorbed into the enterocyte cells.
• 😀 Glucose and galactose are absorbed through the SGLT1 transporter, while fructose is absorbed through GLUT5.
• 😀 Once inside the enterocyte, glucose, galactose, and fructose are transported to the blood via the GLUT2 transporter and reach the liver for further processing.

Q & A

What are the three main types of carbohydrates mentioned in the script?

The three main types of carbohydrates are monosaccharides, disaccharides, and polysaccharides. Monosaccharides are single molecules, disaccharides are two monosaccharides bonded together, and polysaccharides are many monosaccharides bonded together.

What enzyme starts the digestion of starch in the mouth?

Salivary amylase is the enzyme released by the salivary glands in the mouth that starts breaking down starch molecules.

How does the pH of the stomach affect carbohydrate digestion?

The low pH of the stomach inactivates the salivary amylase, meaning that carbohydrate digestion slows or halts temporarily until the food reaches the small intestine.

What role does pancreatic amylase play in carbohydrate digestion?

Pancreatic amylase, released by the pancreas into the small intestine, continues the breakdown of starch molecules into shorter strands of glucose.

What is the role of the brush border or microvilli in carbohydrate digestion?

The brush border or microvilli on enterocyte cells in the small intestine contain enzymes that finish breaking down starch into single glucose molecules, which are ready for absorption.

Which enzymes act on disaccharides, and what are the disaccharides they act on?

The enzymes sucrase, lactase, and maltase act on disaccharides. Sucrase breaks down sucrose (glucose and fructose), lactase breaks down lactose (galactose and glucose), and maltase breaks down maltose (two glucose units).

How are glucose, fructose, and galactose absorbed by the body?

Glucose and galactose are absorbed into enterocyte cells through the SGLT1 transporter, while fructose is absorbed through the GLUT5 transporter. Once inside the cells, they are transported into the bloodstream via the GLUT2 transporter.

What happens to fructose and galactose once they enter the liver?

Fructose and galactose are mainly converted into glucose in the liver.

What are the possible fates of glucose after it enters the bloodstream?

Glucose can be taken up by the liver and stored as glycogen, used by the body as blood glucose for energy, or taken up by muscle cells and stored as muscle glycogen. Excess glucose can also be converted into fat and stored in adipose tissue.

What happens to carbohydrates in terms of energy use once they are absorbed?

After absorption, glucose can be used immediately for energy by cells throughout the body, stored as glycogen in the liver and muscles, or converted into fat for long-term storage.