Glycoproteins and Proteoglycans Flashcards

Questions and Answers

What is a simple sugar? Give examples.

Monosaccharide; examples include glucose, mannose, and galactose.

What is a modified sugar?

Replacing a substituent on the ring with something more reactive.

What are oligosaccharides/polysaccharides?

Polymers of single sugars linked by glycosyltransferases.

What is the difference between glycoproteins and proteoglycans?

Glycoproteins are proteins covalently attached to carbohydrate chains; proteoglycans contain glycosaminoglycan chains linked to a protein core. Signup and view all the answers

What are the main characteristics of glycosylation?

Attaching carbohydrates to proteins; short, branched carbohydrate chains; increases protein solubility. Signup and view all the answers

What is glycosylation biosynthesis and why is it important?

It involves N- or O-linked glycosyl bonds; important for protein solubility and cell surface changes. Signup and view all the answers

How does glycosylation affect blood groups?

Polysaccharide antigen determinants on erythrocytes depend on glycosyltransferases. Signup and view all the answers

Why is glycosylation important for pharmaceuticals?

Altered glycosylation can lead to anaphylaxis or destruction of therapeutic activity. Signup and view all the answers

How does erythropoietin depend on glycosylation?

It is dependent on N-glycosylations; increasing N-glycosylation sites boosts biological activity. Signup and view all the answers

How are glycoproteins degraded?

Through specific glycosidases, starting with exoglycosidases that remove sugars. Signup and view all the answers

What is a lysosomal storage disorder and what is an example?

An inherited genetic defect in enzymes leading to substrate accumulation in lysosomes; e.g., Mucolipidosis II. Signup and view all the answers

What are some broad functions of proteoglycans?

They provide lubrication and support in connective tissue, and contribute to high viscosity and elasticity. Signup and view all the answers

What are the six classes of glycosaminoglycans (GAGs) and their common features?

<ol> <li>Hyaluronic Acid 2. Chondroitin Sulfate 3. Dermatan Sulfate 4. Heparan Sulfate 5. Heparin 6. Keratan Sulfate.</li> </ol> Signup and view all the answers

What are the three major classes of proteoglycans in the extracellular matrix (ECM)?

<ol> <li>Large aggregating proteoglycans 2. Small leucine-rich proteoglycans 3. Basement membrane proteoglycans.</li> </ol> Signup and view all the answers

What is Hyaluronate and what is its function?

A non-complex GAG that acts as a lubricant and shock absorber, mainly found in synovial fluid. Signup and view all the answers

What is Chondroitin Sulfate?

The most abundant GAG, attaching to serine via a tetrasaccharide linkage. Signup and view all the answers

What is Dermatan sulfate?

A GAG consisting of L-iduronic acid found in skin, blood vessels, and heart valves. Signup and view all the answers

How do heparin and heparin sulfate differ from other GAGs?

They have similar disaccharide repeating units but differ in linkages and sulfate groups. Signup and view all the answers

What is important to know about Keratin Sulfate?

KS I is found in the cornea and is N-linked; KS II is found in cartilage and can be N or O linked. Signup and view all the answers

What is Mucopolysaccharidosis and why are they important?

Disorders resulting from lysosomal enzyme deficiencies, leading to sugar accumulation; e.g., Hurler's syndrome. Signup and view all the answers

How are proteoglycans degraded?

Through proteases and glycosidases. Signup and view all the answers

What is the function of aggrecan in articular cartilage?

It binds water to provide compressive strength and enables frictionless movement of bones. Signup and view all the answers

Study Notes

Simple Sugars

Monosaccharides are basic sugars forming the building blocks of carbohydrates; examples include glucose, mannose, and galactose.
D-glucose is a primary energy source for many organisms.

Modified Sugars

Modified sugars involve substituting reactive groups on monosaccharides; for instance, hexosamines introduce nitrogen at C2, like d-galactosamine.

Oligosaccharides and Polysaccharides

Polymers of monosaccharides such as lactose and maltose, which are formed through glycosidic bonds by glycosyltransferases.
Decomposition is performed by glycosidases.

Glycoproteins vs. Proteoglycans

Glycoproteins consist of proteins bound to carbohydrate chains, lacking repetitive sugar units.
Proteoglycans feature glycosaminoglycan (GAG) chains attached to a protein core; they are primarily carbohydrate (95%) and commonly exhibit disaccharide repeat units.

Glycosylation Characteristics

Glycosylation involves attaching carbohydrates to proteins, creating glycoproteins with short, branched chains (12-15 units) that enhance solubility.

Glycosylation Biosynthesis

Involves N- or O-linked glycosylation, enhancing protein solubility and impacting vital biological processes like cell development and fertilization.

Blood Group Antigens

Blood groups are determined by polysaccharide antigens on erythrocytes, influenced by glycosyltransferases; irregular glycosylation can be a disease biomarker.

Glycosylation in Pharmaceuticals

Altered glycosylation of biological drugs can lead to adverse effects such as anaphylaxis; specific examples include Cetuximab and Herceptin.

Erythropoietin and Glycosylation

Recombinant human erythropoietin (rhEPO) for treating anemia depends on N-glycosylation for functional activity.

Glycoprotein Degradation

Glycoproteins are degraded by specific glycosidases, primarily in lysosomes, with malfunctioning enzymes leading to lysosomal storage diseases.

Lysosomal Storage Disorders

Inherited enzyme defects result in substrate accumulation in lysosomes; symptoms include physical deformities and neurological decline. Example: Mucolipidosis II (I-Cell disease).

Functions of Proteoglycans

Proteoglycans possess high anionic charge from uronic acids and sulfates, providing lubrication and structural support in connective tissues.

Classes of Glycosaminoglycans (GAGs)

Primary GAGs include hyaluronic acid, chondroitin sulfate, dermatan sulfate, heparan sulfate, heparin, and keratin sulfate, with disaccharide repeats and sulfate groups.

Major Classes of Proteoglycans in ECM

Categories include large aggregating proteoglycans (aggrecan), small leucine-rich proteoglycans, and basement membrane proteoglycans (perlecan).

Hyaluronate

Non-sulfated GAG with disaccharide units, it serves as a lubricant and shock absorber, particularly in synovial fluid.

Chondroitin Sulfate

Most abundant GAG, integral to cartilage and connective tissues, aggregates with hyaluronate.

Dermatan Sulfate

Characterized by L-iduronic acid, commonly found in connective tissues such as skin and blood vessels.

Heparin and Heparan Sulfate

Display unique disaccharide linkages; heparin acts as an intracellular anticoagulant and is involved in blood vessel functionality.

Keratin Sulfate

Exists in two forms (KS I and KS II) and is linked to corneal and cartilage structures.

Mucopolysaccharidosis

Genetic disorders leading to the accumulation of proteoglycan sugars, detectable prenatal; examples include Hurler's and Sanfilippo syndromes.

Proteoglycan Degradation

Degraded via proteases and glycosidases.

Aggrecan in Articular Cartilage

Functions as a structural element within cartilage, retaining water to provide compressive strength and facilitate smooth bone movement.

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Description

Explore the essential concepts of glycoproteins and proteoglycans through this flashcard quiz. Understand the definitions and examples of monosaccharides and modified sugars. Enhance your knowledge in biochemistry and molecular biology effectively with these key terms.