Glycosaminoglycans & Glycoproteins Overview

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Questions and Answers

What is the role of glycosaminoglycans (GAGs) in the body's ground substance?

Serving as essential components of cell surfaces

Binding large amounts of water to produce a gel-like matrix (correct)

Promoting cell-cell signaling and adhesion

Acidic sugar-amino sugar chains

What is the main difference between proteoglycans and glycoproteins?

Protein content is greater in proteoglycans than in glycoproteins

Proteoglycans bind large amounts of water, while glycoproteins do not

Carbohydrate content is greater in proteoglycans than in glycoproteins (correct)

Glycoproteins serve as essential components of cell surfaces

Which of the following is a characteristic feature of glycosaminoglycans (GAGs)?

Unbranched heteropolysaccharide chains composed of repeating disaccharide units (correct)

High protein content with minimal carbohydrate components

Absence of carboxyl and sulfate groups

Neutral charge due to acetylation of NH2 group

What is the significance of the presence of carboxyl and sulfate groups in GAGs?

Imparts strongly negative nature to GAGs Signup and view all the answers

Which amino sugar is commonly found in the structure of glycosaminoglycans (GAGs)?

D-glucosamine or D-galactosamine Signup and view all the answers

What is the general function of glycosaminoglycans (GAGs) as related to their large number of negative charges?

Repel each other and are surrounded by a shell of water molecules Signup and view all the answers

What contributes to the slippery consistency of mucous secretions and synovial fluid?

The slipping past of GAGs when brought together Signup and view all the answers

How many classes are GAGs classified into based on monomeric composition, type of glycosidic linkages, and degree and location of sulfate units?

Six Signup and view all the answers

What do proteoglycan monomers associate with to form proteoglycan aggregates?

Hyaluronic acid Signup and view all the answers

How are the polysaccharide chains elongated during the synthesis of GAGs?

By the sequential addition of alternating UDP derivatives of acidic & amino sugars Signup and view all the answers

What stabilizes the association between proteoglycan monomers and hyaluronic acid to form proteoglycan aggregates?

Link proteins Signup and view all the answers

In which cellular organelles does the synthesis of GAGs occur?

ER & Golgi Signup and view all the answers

Which sugar replaces a hydroxyl group of F-6-P to form N-Acetylglucosamine (GlcNAc) and N-acetylgalactosamine (GalNAc)?

Glutamine Signup and view all the answers

What type of bond is formed between the carbohydrate chain and the protein in the proteoglycan monomer?

O-glycosidic bond Signup and view all the answers

Study Notes

Role of GAGs in Ground Substance

GAGs play a crucial role in maintaining the body's ground substance, providing structural support and facilitating cell-cell interactions.
They act as a hydrated gel-like matrix, allowing for the diffusion of nutrients, waste, and signaling molecules.

Proteoglycans vs. Glycoproteins

The main difference between proteoglycans and glycoproteins is the presence of a long, unbranched polysaccharide chain (GAG) in proteoglycans.
Glycoproteins, on the other hand, have shorter, branched oligosaccharide chains.

Characteristics of GAGs

GAGs are characterized by the presence of carboxyl and sulfate groups, which impart a high negative charge density.
This high negative charge density is responsible for the retention of water and the creation of a hydrated gel-like matrix.

Significance of Carboxyl and Sulfate Groups

The presence of carboxyl and sulfate groups in GAGs is significant, as they:
- Attract and retain water, creating a hydrated matrix.
- Provide a negative charge, influencing the behavior of surrounding molecules.

Amino Sugars in GAGs

Glucosamine and galactosamine are the two amino sugars commonly found in the structure of GAGs.

Function of GAGs

The large number of negative charges in GAGs allows them to:
- Attract and retain water, creating a hydrated matrix.
- Interact with positively charged molecules, influencing cell behavior.

Consistency of Mucous Secretions and Synovial Fluid

The slippery consistency of mucous secretions and synovial fluid is due to the presence of GAGs, particularly hyaluronic acid.

Classification of GAGs

GAGs are classified into several classes based on:
- Monomeric composition.
- Type of glycosidic linkages.
- Degree and location of sulfate units.

Proteoglycan Aggregates

Proteoglycan monomers associate with hyaluronic acid to form proteoglycan aggregates.
These aggregates are stabilized by the interaction between proteoglycan monomers and hyaluronic acid.

Synthesis of GAGs

The polysaccharide chains are elongated during GAG synthesis through the addition of monosaccharide units.
This process occurs in the Golgi apparatus and endoplasmic reticulum.

Synthesis of Amino Sugars

Glucosamine-6-phosphate (GlcN-6-P) is converted into N-Acetylglucosamine (GlcNAc) by replacing a hydroxyl group with an acetyl group.
Similarly, galactosamine-6-phosphate (GalN-6-P) is converted into N-Acetylgalactosamine (GalNAc).

Proteoglycan Monomer Structure

The carbohydrate chain is attached to the protein in the proteoglycan monomer through a glycosidic bond.

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Description

Test your knowledge about the structure, function, and properties of glycosaminoglycans and glycoproteins. Explore the role of these molecules in forming the body's ground substance and cell surfaces.