Carbohydrate Digestion Overview

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Questions and Answers

What is the main function of salivary alpha-Amylase during carbohydrate digestion?

To initiate the breakdown of proteins

To neutralize stomach acid before entering the small intestine

To hydrolyze glycosidic bonds between monosaccharides

To break down starch into smaller oligosaccharides (correct)

Which enzyme is responsible for hydrolyzing lactose into its monosaccharide components?

Maltase

Sucrase

Lactase (correct)

Isomaltase

What types of dietary carbohydrates are primarily metabolized to monosaccharides?

Oligosaccharides, Starch, and Disaccharides

Starch, Sucrose, and Cellulose

Lactose, Glucose, and Fructose

Starch, Sucrose, and Lactose (correct)

Which enzyme does NOT attack alpha-1,6 linkages during carbohydrate digestion?

Pancreatic alpha-amylase Signup and view all the answers

Where in the digestive system does the majority of carbohydrate digestion occur?

Mouth and small intestines Signup and view all the answers

Which final product of carbohydrate digestion is NOT a monosaccharide?

Maltotriose Signup and view all the answers

In which parts of the digestive system is the majority of dietary sugar absorbed?

Duodenum and Upper Jejunum Signup and view all the answers

What mechanism allows the completion of carbohydrate digestion at the intestinal mucosal lining?

Hydrolysis by disaccharidases Signup and view all the answers

Which statement is true about glycogen as a dietary carbohydrate?

It is stored in animal tissues. Signup and view all the answers

What is the primary method by which D-Galactose, D-Glucose, and D-Fructose are transported into intestinal mucosal cells?

Active transport requiring energy Signup and view all the answers

What happens when there is a specific disaccharidase deficiency?

Disaccharides remain undigested in the intestine. Signup and view all the answers

What occurs to alpha-amylase in the stomach due to high acidity?

It is inactivated, halting carbohydrate digestion. Signup and view all the answers

What is the role of bicarbonate in the small intestine during carbohydrate digestion?

To neutralize stomach acid Signup and view all the answers

What effect do undigested carbohydrates have in the large intestine?

Creation of an osmotic effect drawing water into the lumen Signup and view all the answers

What role does sodium (Na+) play in the absorption of monosaccharides in the intestinal mucosal cells?

Is required for concurrent uptake during absorption Signup and view all the answers

How do monosaccharides exit the mucosal cells after absorption?

Through facilitated transport and simple diffusion Signup and view all the answers

What is a consequence of bacterial fermentation of remaining undigested carbohydrates in the large intestine?

Production of 2- to 3-carbon compounds that are osmotically active Signup and view all the answers

What is the primary reason for osmotic diarrhea in cases of abnormal disaccharide degradation?

Undigested carbohydrates draw water into the intestinal lumen Signup and view all the answers

Which characteristic describes the transport systems for monosaccharides in the intestinal mucosa?

Both active transport and facilitated diffusion are involved Signup and view all the answers

What is NOT a factor involved in the active transport of monosaccharides into mucosal cells?

Concentration gradient Signup and view all the answers

What primary function does GLUT-7 serve in the body?

Transporting fructose in the small intestines Signup and view all the answers

Which GLUT transporter is primarily responsible for glucose transport in neurons?

GLUT-3 Signup and view all the answers

How does GLUT-4 activity change in response to insulin?

Increases in number and activity Signup and view all the answers

Which GLUT transporter is involved in the transport of glucose against its concentration gradient?

GLUT-2 Signup and view all the answers

Which GLUT isoform is abundant in red blood cells and the brain?

GLUT-1 Signup and view all the answers

In which tissue is GLUT-7 predominantly expressed?

Liver and gluconeogenic tissues Signup and view all the answers

What is the transport mechanism associated with Na+-Monosaccharide Cotransport System?

Cotransport with sodium ions Signup and view all the answers

Which GLUT isoform is primarily responsible for glucose uptake from blood into cells under high glucose conditions?

GLUT-2 Signup and view all the answers

Which GLUT isoform is considered insulin-responsive?

GLUT-4 Signup and view all the answers

What is the primary transport mechanism of glucose by GLUT transporters?

Facilitated diffusion from high to low concentration Signup and view all the answers

What type of transport system specifically transports D-fructose?

Na+-Independent Monosaccharide Transport System Signup and view all the answers

What is the main treatment for lactose intolerance?

Remove lactose from the diet Signup and view all the answers

Which compound is known to inhibit the Na+-Dependent Monosaccharide Cotransport System?

Phlorhizin Signup and view all the answers

Which of the following is NOT a hereditary defect related to monosaccharide transport?

Generalized malnutrition Signup and view all the answers

What is typically measured in the breath to diagnose carbohydrate malabsorption?

H2 gas levels Signup and view all the answers

What results from a deficiency in brush border enzymes?

Severe diarrhea Signup and view all the answers

In which population is lactose intolerance most prevalent?

Blacks and Asians Signup and view all the answers

What type of transport system is utilized for the exit of monosaccharides from epithelial cells?

Na+-Independent transport Signup and view all the answers

What is the recommended treatment for Isomaltase-Sucrase deficiency?

Remove sucrose from the diet Signup and view all the answers

What does cytochalasin B inhibit with respect to monosaccharide transport?

Na+-Independent transport of fructose Signup and view all the answers

Study Notes

Overview of Carbohydrate Digestion

Digestion begins in the mouth with starch.
Major dietary carbohydrates: Starch, Sucrose, Lactose.
Digestive enzymes convert carbohydrates to monosaccharides.
Stomach acid inactivates salivary alpha-amylase, halting carbohydrate digestion temporarily.
Carbohydrate digestion completes before contents reach the duodenojejunal junction.
Principal digestion sites: Mouth and intestinal lumen.
Brush border enzymes digest sucrose, lactose, and starch products.

Enzymatic Breakdown

Endoglycosidases and glycosidases play key roles in breaking down oligosaccharides and polysaccharides.
Final digestion products: D-glucose, D-galactose, and D-fructose.
Enzymes synthesized in intestinal mucosa include:
- Isomaltase, Maltase, Sucrase, Lactase for disaccharide cleavage.

Monosaccharide Absorption

Absorption occurs mainly in the duodenum and upper jejunum.
Monosaccharides transported into mucosal cells via active transport, involving sodium ions.
Na+-Dependent Cotransport System specific for D-galactose and D-glucose.
Na+-Independent System transports D-fructose by facilitated diffusion.

Transport Mechanisms

Monosaccharides exit epithelial cells through Na+-independent transport.
Specific defects in disaccharidase can lead to osmotic diarrhea and flatulence due to undigested carbohydrates.
Common transporters: GLUT-1 to GLUT-14, facilitating glucose transport:
- GLUT-1: Found in RBCs and brain.
- GLUT-2: In liver, kidney, pancreatic β cells.
- GLUT-3: Main glucose transporter in neurons.
- GLUT-4: Abundant in adipose tissue and skeletal muscles; insulin increases activity.
- GLUT-5: Primarily involved in fructose transport.

Intestinal Disorders and Diagnostics

Lactose intolerance affects over half of adults, especially among Black and Asian populations.
Diagnosis involves Oral Tolerance Tests and H2 Gas Measurement in breath.
Specific disaccharidase deficiencies can lead to malabsorption and osmotic diarrhea.

Key Functions of GLUT Transporters

GLUT-2 balances glucose transport based on blood levels.
GLUT-4 is insulin-responsive, enhancing glucose uptake during high levels.
GLUT-7 mediates glucose transport within the endoplasmic reticulum.

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Description

This quiz covers the process of carbohydrate digestion, starting from the mouth and including the role of digestive enzymes in breaking down carbohydrates into monosaccharides. Students will learn about the key enzymes involved, the sites of digestion, and how monosaccharides are absorbed in the intestines.