Biochemistry: Carbohydrates and Glycoproteins

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Questions and Answers

What is the primary amino acid residue where N-linked oligosaccharides are covalently linked to proteins?

Tyr

Asn (correct)

Gly

Ser

During which cellular process are N-linked sugars typically attached to proteins in the form of a 14 residue oligosaccharide?

Translation (correct)

Replication

Translation and Transcription

Transcription

Which of the following statements accurately describes the process of N-linked glycosylation?

It occurs in the endoplasmic reticulum. (correct)

It begins in the Golgi apparatus.

It occurs exclusively in the cytoplasm.

Oligosaccharides are added one sugar at a time.

In the context of glycoproteins, what role do peptidoglycans play?

They serve as a structural component in cell walls. Signup and view all the answers

Which of the following is NOT a mechanism by which oligosaccharides can attach to proteins?

C-terminal glycosylation Signup and view all the answers

What characterizes the recognition site for N-linked glycosylation?

X can be any amino acid except Pro. Signup and view all the answers

What type of polysaccharide is heparin classified as in terms of glycoproteins?

A glycosaminoglycan. Signup and view all the answers

What modification occurs to glycoproteins in the Golgi apparatus?

N-linked oligosaccharide trimming. Signup and view all the answers

Which statement correctly describes the role of sialic acids in biochemistry?

They are important constituents of glycoproteins and glycolipids. Signup and view all the answers

What type of bond is formed by the reaction between an alcohol and the anomeric center of a carbohydrate?

Glycosidic bond Signup and view all the answers

What characterizes a reducing sugar in the context of saccharides?

The ability to donate electrons to other molecules. Signup and view all the answers

In N-linked glycosylation, which amino acid is primarily involved in the attachment of oligosaccharides?

Asparagine Signup and view all the answers

Which of the following defines a glucoside?

A glycosidic compound derived from glucose. Signup and view all the answers

What is the structural characteristic of D-allose as an aldohexose?

It has six carbon atoms, one being aldehyde. Signup and view all the answers

Which modification prevents -D-allopyranose from mutarotating?

Methylation of a hydroxyl group. Signup and view all the answers

Which of the following amino acids is NOT typically involved in O-linked glycosylation?

Lysine Signup and view all the answers

What structural feature differentiates hyaluronic acid from other glycosaminoglycans?

It is composed of repeating disaccharide units of N-acetyl-glucosamine and glucuronic acid. Signup and view all the answers

Which amino acid is commonly involved in the attachment of O-linked oligosaccharides?

Threonine Signup and view all the answers

What type of proteins specifically bind to carbohydrates?

Lectins Signup and view all the answers

In the context of glycoproteins, what type of glycosylation involves the attachment of sugars to nitrogen atoms?

N-linked glycosylation Signup and view all the answers

Which sugar configuration indicates most carbohydrates in living organisms are in the D-form?

D-configured Signup and view all the answers

What is the primary structural feature of hyaluronic acid?

It is a linear polysaccharide composed of repeating disaccharide units. Signup and view all the answers

Which amino acid's hydroxyl group can form O-linked glycosidic bonds in glycoproteins?

Serine Signup and view all the answers

What is the significance of the specific carbohydrate-binding proteins in biological systems?

They mediate cell-cell recognition and signaling. Signup and view all the answers

Which type of glycosylation is characterized by the attachment of oligosaccharides to serine or threonine residues?

O-linked glycosylation Signup and view all the answers

Which of the following best describes the role of hyaluronic acid in biological systems?

It acts as a lubricant and shock absorber in connective tissues. Signup and view all the answers

What is the relationship between glycoprotein structure and cellular function?

Glycoprotein structure is critical for proper function and recognition. Signup and view all the answers

What distinguishes glycoproteins from other protein types?

They exhibit microheterogeneity due to varied sugar attachments. Signup and view all the answers

Which disaccharide is the smallest aldose found in living organisms?

D-glyceraldehyde Signup and view all the answers

In N-linked glycosylation, which structure is primarily attached to the nitrogen of asparagine residues?

N-acetylglucosamine Signup and view all the answers

Which of the following polysaccharides is characterized as a heteropolysaccharide?

Hyaluronic acid Signup and view all the answers

Which mechanism is most commonly associated with oligosaccharide attachment in glycoproteins?

Addition through enzymatic glycosylation. Signup and view all the answers

What is the primary structural characteristic of hyaluronic acid?

It is a homopolymer of glucuronic acid and N-acetyl-D-glucosamine. Signup and view all the answers

Which type of glycosylation involves the attachment of carbohydrates to nitrogen in amino acids?

N-linked glycosylation Signup and view all the answers

In the context of glycoprotein structure, what is the role of oligosaccharide chains?

They play a critical role in protein folding and stability. Signup and view all the answers

Which monosaccharide is a common building block of glycoproteins in N-linked glycosylation?

Mannose Signup and view all the answers

Which of the following is NOT a typical feature of O-linked glycosylation?

Localized primarily in the endoplasmic reticulum. Signup and view all the answers

What type of oligosaccharide modifications can impact cellular signaling and recognition?

Glycosylation patterns Signup and view all the answers

Which of the following statements about chitin is accurate?

Chitin is classified as a polysaccharide made of N-acetyl-D-glucosamine. Signup and view all the answers

The disaccharide commonly found in dairy products and made of glucose and galactose is known as?

Lactose Signup and view all the answers

Which is a key difference between epimers and anomers in carbohydrate chemistry?

Anomers are a specific type of epimer. Signup and view all the answers

What is a characteristic of bulky substituents in chair conformations of cyclohexane derivatives?

They prefer equatorial positions for stability. Signup and view all the answers

Study Notes

Monosaccharides

Glucose has sixteen possible stereoisomers due to its four chiral carbon atoms.
The smallest aldose is glyceraldehyde.
α-D-galactose and β-D-galactose are anomers.
Bulky ring substituents prefer equatorial positions in chair conformations.
Deoxy sugars have a hydroxyl group replaced with a hydrogen atom.
The bonding of alcohols to the anomeric center of a carbohydrate forms a glycosidic bond.
A saccharide with a free aldehyde group is a reducing sugar.

Polysaccharides

Lactose is a disaccharide commonly found in dairy products.
Chitin is a homopolymer of (1-4)-linked N-acetyl-D-glucosamine, a key structural component in invertebrate exoskeletons.
α-amylose adopts a helically coiled conformation.
Starch is a mixture of α-amylose and amylopectin.
Hyaluronic acid is an example of a heteropolysaccharide.

Glycoproteins

Bacterial cell walls contain peptidoglycans.
N-linked oligosaccharides connect to proteins at asparagine (Asn) residues.
N-linked glycosylation attaches a 14-residue oligosaccharide to proteins during translation in the endoplasmic reticulum.
The recognition site for N-linked glycosylation is Asn-X-Ser/Thr (where X is any amino acid except Proline).
O-linked oligosaccharides commonly attach to the hydroxyl group of threonine.
Lectins are proteins that bind to specific carbohydrates.
Glycoproteins exhibit microheterogeneity and are assembled under strict genetic control. They are typically less than 1% carbohydrate by weight.

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Description

Test your knowledge on monosaccharides, polysaccharides, and glycoproteins. This quiz covers essential structural features and classifications of various carbohydrates, including their roles in biology. Explore their properties and significance in biochemical processes.