Carbohydrate Digestion Overview

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Questions and Answers

Which part of the intestine is primarily responsible for absorbing the bulk of dietary sugars?

Duodenum and Upper Jejunum (correct)

Cecum

Ileum

Rectum

What is the process by which D-galactose, D-glucose, and D-fructose are transported into mucosal cells?

Active transport requiring energy (correct)

Facilitated diffusion

Simple diffusion

Passive transport

What results from a specific disaccharidase deficiency?

Increased absorption of monosaccharides

Enhanced degradation of carbohydrates

Improved intestinal permeability

Accumulation of undigested disaccharides (correct)

What effect does the passage of undigested carbohydrates into the large intestine have?

Osmotic effect causing diarrhea Signup and view all the answers

What is required alongside the uptake of monosaccharides to facilitate their transport into mucosal cells?

Sodium Signup and view all the answers

What is the primary role of GLUT-7?

Transport fructose in the small intestines and testes Signup and view all the answers

How do monosaccharides leave the mucosal cells?

Simple diffusion and facilitated transport Signup and view all the answers

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

GLUT-1 Signup and view all the answers

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

Formation of osmotically active compounds Signup and view all the answers

How does GLUT-2 function when blood glucose levels are low?

Transport glucose from cells to the blood Signup and view all the answers

What characterizes the transport proteins involved in the absorption of sugars within intestinal cells?

They undergo saturation at high substrate concentrations. Signup and view all the answers

What is a primary function of the disaccharidases in the digestive system?

Degrade disaccharides to monosaccharides Signup and view all the answers

What is the mechanism of glucose movement mediated by GLUT transporters?

Transport from high to low glucose concentration Signup and view all the answers

Which of the following statements about osmotic diarrhea is accurate?

It can be caused by the fermentation of carbohydrates in the intestine. Signup and view all the answers

Which GLUT transporter is increased in number and activity by insulin?

GLUT-4 Signup and view all the answers

What type of process does the Na+-Monosaccharide Cotransport System represent?

Active transport Signup and view all the answers

Which GLUT transporter primarily facilitates glucose uptake in neurons?

GLUT-3 Signup and view all the answers

What is a key characteristic of GLUT-5?

Transports fructose exclusively Signup and view all the answers

Which GLUT isoform is associated with energy-requiring glucose transport?

GLUT-2 Signup and view all the answers

Which tissue is GLUT-4 primarily abundant in?

Adipose tissues and skeletal muscles Signup and view all the answers

What is the primary role of salivary alpha-amylase in carbohydrate digestion?

To initiate the breakdown of starch Signup and view all the answers

Which carbohydrate does not get attacked by pancreatic alpha-amylase?

Isomaltose Signup and view all the answers

Which product is not a final product of carbohydrate digestion?

Sucrose Signup and view all the answers

What occurs to stomach contents as they move into the small intestine?

They are neutralized by bicarbonate Signup and view all the answers

Which enzyme is responsible for breaking down isomaltose?

Isomaltase Signup and view all the answers

What is the fate of disaccharides in the upper jejunum?

They are hydrolyzed to monosaccharides Signup and view all the answers

Which of the following enzymes is critical for lactose hydrolysis?

Beta-glucosidase Signup and view all the answers

What type of bonds do endoglycosidases specifically break down?

Glycosidic bonds Signup and view all the answers

Where does the principal site of dietary carbohydrate digestion occur?

Mouth and small intestine Signup and view all the answers

What are the major dietary polysaccharides mentioned?

Glycogen and Starch Signup and view all the answers

What inhibits the Na+-Dependent Monosaccharide Cotransport System?

Phlorhizin Signup and view all the answers

Which of the following conditions is associated with a deficiency in brush border enzymes?

Generalized Defects Signup and view all the answers

What type of transport system is responsible for the uptake of 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 of the following is a diagnostic method for carbohydrate absorption issues?

H2 Gas Measurement in the Breath Signup and view all the answers

What is the likely outcome of malnutrition in relation to monosaccharide transport?

Decreased levels of brush border enzymes Signup and view all the answers

Which population has the highest reported incidence of lactose intolerance?

Blacks and Asians Signup and view all the answers

The Na+-Independent transport for D-galactose and D-glucose occurs through which mechanism?

Facilitated diffusion Signup and view all the answers

Which of the following is NOT a consequence of hereditary defects in monosaccharide transport?

Hormonal imbalance Signup and view all the answers

What condition results from a deficiency of isomaltase-sucrase?

Sucrose intolerance 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

Explore the process of carbohydrate digestion, starting from the mouth to the intestinal lumen. This quiz covers key aspects such as enzymatic breakdown, major dietary carbohydrates, and the absorption of monosaccharides. Test your understanding of the roles of various enzymes in breaking down complex carbohydrates.