Carbohydrates Flashcards Quiz

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Questions and Answers

Which item is NOT associated with disaccharides?

O-glycosidic linkages

Never having free anomeric carbons (correct)

Formation of a ketal or acetal

Sucrose

Homopolysaccharides contain a single monomeric sugar species.

True

What O-glycosidic bond is commonly found in amylose, amylopectin, and glycogen?

(α16)

(β14)

(β16)

(α14) (correct)

A glycogen molecule with 28 branches has how many nonreducing and reducing ends?

29 nonreducing ends and 1 reducing end Signup and view all the answers

Why is it logical for sugars to be added to only one end of glycogen?

Because there are many nonreducing ends on one molecule, allowing rapid glucose storage and release. Signup and view all the answers

Even though amylose and cellulose are made of similar homopolysaccharide chains, they have very different properties. Why?

The β-glycosidic linkage of glucose molecules in cellulose forms interchain and intrachain hydrogen bonds. Signup and view all the answers

What structural features do cellulose and glycogen share, and in what ways do they differ?

Both are polymers of D‑glucose, but cellulose is connected by (β1→4) glycosidic linkages, whereas glycogen is connected by (α1→4) glycosidic linkages. Signup and view all the answers

What structural features do D‑glucose and D‑fructose share, and in what ways do they differ?

Both are hexoses, but glucose is an aldohexose, whereas fructose is a ketohexose. Signup and view all the answers

What structural features do maltose and sucrose share, and in what ways do they differ?

Both are disaccharides, but maltose has two (α1→4) linked D‑glucose units, whereas sucrose has (α1↔2β) linked D‑glucose and D‑fructose. Signup and view all the answers

Select the statements that accurately describe the differences between a hemiacetal and a glycoside.

A hemiacetal forms when an aldose condenses with an alcohol. Signup and view all the answers

What chemical property of fructose could account for the decreased sweetness at high temperatures?

Fructose cyclizes to either the pyranose or the furanose structure. Signup and view all the answers

Why does sucrose not have any anomeric forms?

Sucrose has no free anomeric carbon to undergo mutarotation. Signup and view all the answers

Select all of the sugars that are classified as reducing sugars.

D-lactose Signup and view all the answers

Classify each characteristic as describing glycoproteins or proteoglycans.

Glycoproteins = May contain N-linked glycosidic bonds Proteoglycans = Include the heparan sulfate family Signup and view all the answers

What amino acid residues of antithrombin III are likely to interact with heparin?

Positively charged residues. Signup and view all the answers

What is glucosyl?

Univalent radical derived from the hemiacetal form of glucose. Signup and view all the answers

What is a lectin?

A protein that binds a carbohydrate, commonly an oligosaccharide, with very high affinity and specificity. Signup and view all the answers

A(n) is a(n) with two monosaccharide units.

disaccharide; oligosaccharide Signup and view all the answers

What chemical feature determines if a sugar is an aldose or a ketose?

the position of the carbonyl carbon Signup and view all the answers

Glucose is a monosaccharide with a(n):

aldehyde functional group and six carbons Signup and view all the answers

Why does (R,S)-aspartame NOT stimulate the sweet receptor?

Site X cannot accommodate the hydrophobic benzene ring. Signup and view all the answers

Which statement is false regarding the enantiomers of glyceraldehyde?

Glyceraldehyde does not occur in optically active isomeric forms. Signup and view all the answers

A monosaccharide with a ketone functional group and seven carbons:

is a ketoheptose. Signup and view all the answers

What name is given to monosaccharides that differ in configuration about the hemiacetal carbon atom?

anomers Signup and view all the answers

Cyclization of monosaccharides:

is the reaction of hemiketal or hemiacetal formation. Signup and view all the answers

Using the Fischer projection of D-glucose, identify which statement is true of the Haworth perspective formula of α-D-glucopyranose.

The anomeric hydroxyl is on the opposite side from C-6. Signup and view all the answers

Which reaction is one that is NOT common of glucose?

oxidation by reducing sugars Signup and view all the answers

What term is given to carbohydrates linked by their anomeric carbons?

nonreducing sugars Signup and view all the answers

Even though amylose and cellulose are made of similar homopolysaccharide chains, they have very different properties. Why?

The β-glycosidic linkage of glucose molecules in cellulose forms interchain and intrachain hydrogen bonds that produce straight, stable fibers that exclude water. Signup and view all the answers

Why are chitin and cellulose hydrophobic and essentially insoluble in an aqueous media?

Because they form many internal hydrogen bonds, they leave no sites for binding to water. Signup and view all the answers

Polysaccharides:

are glycans. Signup and view all the answers

Which characteristic is NOT one that is true of glycosaminoglycans?

always contain sulfates Signup and view all the answers

The glycosaminoglycan hyaluronan:

consists of alternating residues of D-glucuronic acid and N-acetylglucosamine. Signup and view all the answers

Which statement about glycoconjugates is false?

Glycolipids are found in specific organelles, such as Golgi complexes. Signup and view all the answers

Which statement about proteoglycans is false?

They are always extracellular. Signup and view all the answers

A laboratory is studying the binding properties of a glycoprotein on the plasma membrane. What amino acids should they analyze for the presence of branched heteropolysaccharides?

Ser, Thr, and Asn Signup and view all the answers

Glycoproteins:

are sometimes intracellular. Signup and view all the answers

Which of these is NOT a glycoconjugate?

trehalose Signup and view all the answers

Oligosaccharides are:

found in bacterial lipopolysaccharides. Signup and view all the answers

Glycosaminoglycans?

<ul> <li>heteropolysaccharides in ECM</li> <li>linear polymers composed of repeating disaccharide units</li> <li>one monosaccharide is always either N-acetylglucosamine or N-acetylgalactosamine and the other is usually a uronic acid</li> <li>some contain esterified sulfate groups</li> <li>unique to animals and bacteria</li> </ul> Signup and view all the answers

Types of glycosaminoglycans?

<ol> <li>Hyaluronic acid</li> <li>Chondroitin-4-sulfate</li> <li>Chondroitin-6-sulfate</li> <li>Heparin sulfate</li> <li>Heparan sulfate</li> <li>Dermatan sulfate</li> <li>Keratan sulfate</li> </ol> Signup and view all the answers

Hyaluronan?

<ul> <li>aka hyaluronic acid</li> <li>alternating residues of D-glucuronic acid and N-acetylglucosamine</li> </ul> Signup and view all the answers

Uronic acid?

Uronic acids are sugars where the CH2OH group has been oxidized to form a carboxylic acid group. They can be hexuronic acids or penturonic acids depending on whether they are derived from hexoses or pentoses. Signup and view all the answers

Distinctions between hyaluronan and heparan, chondroitin, etc. sulfates?

<ul> <li>shorter polymers</li> <li>covalently linked to specific proteins (proteoglycans)</li> <li>one or both monomer units differ from hyaluronan</li> </ul> Signup and view all the answers

How does heparan sulfate bind to proteins?

Sulfated residues give the molecule the ability to interact specifically with proteins. Signup and view all the answers

Heparan?

<ul> <li>highly sulfated intracellular form of heparan sulfate</li> <li>produced by mast cells</li> <li>used as anticoagulant because it binds antithrombin which enables it to bind thrombin and prevent formation of a clot</li> </ul> Signup and view all the answers

Glycoconjugate?

Biologically active molecule consisting of an informational carbohydrate joined to a protein or lipid. Signup and view all the answers

Proteoglycans?

Macromolecules of the cell surface or extracellular matrix consisting of one or more sulfated glycosaminoglycan chains joined covalently to a membrane protein or secreted protein. Signup and view all the answers

Glycoprotein?

<ul> <li>one or several oligosaccharides joined covalently to a protein</li> <li>found on the outer face of the plasma membrane, in the ECM, in blood, in organelles (Golgi complex, secretory granules, lysosomes)</li> <li>oligosaccharide portions are heterogeneous and rich in info</li> </ul> Signup and view all the answers

Glycosphingolipids?

Class of glycolipids with a specific backbone structure <ul> <li>neurons are rich in glycosphingolipids</li> <li>play a role in signal transduction</li> </ul> Signup and view all the answers

How do glycosaminoglycans connect to proteins?

A tetrasaccharide linker connects glycosaminoglycan to a Ser residue of the protein. Signup and view all the answers

Two families of membrane heparan sulfate proteoglycans?

Syndecans - single transmembrane domain and an extracellular domain bearing 3-5 chains of heparan sulfate and chondroitin sulfate Glypicans - attached to the membrane by a GPI anchor. Signup and view all the answers

GPI anchor?

<ul> <li>glycosylated derivative of the membrane lipid phosphatidylinositol</li> </ul> Signup and view all the answers

Antithrombin binds to and inhibits the protease thrombin only in the presence of heparan sulfate.

True Signup and view all the answers

How does heparan sulfate bind antithrombin?

<ul> <li>Antithrombin and thrombin are rich in Arg and Lys residues, which interact electrostatically with the sulfates of glycosaminoglycans.</li> </ul> Signup and view all the answers

Proteoglycan aggregates?

Supramolecular assemblies of many core proteins all bound to a single molecule of hyaluronan <ul> <li>Aggrecan interacts strongly with collagen in the ECM of cartilage.</li> </ul> Signup and view all the answers

Two types of attachments for oligosaccharides in glycoproteins?

O-linked: glycoside bond joins the anomeric carbon of a carbohydrate to the -OH of a Ser or Thr residue N-linked: an N-glycosyl bond joins the anomeric carbon of a sugar to the amide nitrogen of an Asn residue. Signup and view all the answers

Examples of glycoproteins?

Mucins: secreted or membrane glycoproteins <ul> <li>Can contain large numbers of O-linked oligosaccharide chains</li> <li>Present in most secretions Proteins of blood: immunoglobulins, follicle-stimulating hormone, luteinizing hormone, thyroid-stimulating hormone Milk proteins: major whey protein a-lactalbumin</li> </ul> Signup and view all the answers

Which statement about selectins is false?

They are intracellular. Signup and view all the answers

Lectins:

often bind their ligands via multiple weak interactions. Signup and view all the answers

The ________ does NOT need to be determined in fully characterizing oligosaccharides and polysaccharides.

amino acid sequence of the protein Signup and view all the answers

Which of these sugars is nonreducing?

trehalose Signup and view all the answers

Study Notes

Carbohydrates Overview

Oligosaccharides consist of short chains of monosaccharides linked via glycosidic bonds; the most common are disaccharides (two monosaccharide units).
Monosaccharides can be classified as aldoses or ketoses based on the position of the carbonyl carbon; aldoses have the carbonyl at the end, ketoses have it at any other position.

Monosaccharide Characteristics

Glucose is an aldohexose, containing an aldehyde group and six carbon atoms.
A monosaccharide with a ketone functional group and seven carbons is called a ketoheptose.
Anomers are monosaccharides differing only at the hemiacetal carbon configuration.
Cyclization of monosaccharides leads to ring structures through the formation of hemiacetals or hemiketals.

Glycosidic Bonds and Nonreducing Sugars

When the anomeric carbon forms a glycosidic bond, the sugar becomes a nonreducing sugar due to the lack of free anomeric carbons.
Proteins decorated with carbohydrates (glycoproteins) can be enriched in certain amino acids like Ser, Thr, and Asn for oligosaccharide attachment.

Polysaccharides

Polysaccharides, also known as glycans, can be homopolysaccharides (same monosaccharide units) or heteropolysaccharides (different monosaccharide units).
Cellulose features β-glycosidic linkages that create strong fibers through hydrogen bonding, while amylose forms helices through α-glycosidic linkages.

Glycosaminoglycans

Glycosaminoglycans (GAGs) are linear polymers of repeating disaccharide units often found in the extracellular matrix.
Hyaluronan, a type of GAG, consists of alternating D-glucuronic acid and N-acetylglucosamine residues and is important for tissue hydration.

Glycoproteins and Glycoconjugates

Glycoproteins can have one or several oligosaccharides covalently linked, influencing their structure and function in biological processes.
Glycoconjugates comprise carbohydrates linked to proteins or lipids, playing critical roles in cell recognition and signaling.

Special Terms and Functions

Heparan sulfate is a GAG involved in various cellular processes, including binding to antithrombin to inhibit clot formation.
Selectins mediate immunological functions and cell recognition, being found on the plasma membrane but are not intracellular.

Sugar Reducing Properties

Nonreducing sugars do not have free anomeric carbons; trehalose, a disaccharide, is an example.
Glycosidic linkages (like α1→4 in amylose and glycogen) determine the structure and properties of polysaccharides.

Summary of Key Functionalities

Proteoglycans are macromolecules made of proteins and sulfated GAGs, important in extracellular interactions and stability.
Antithrombin binding to heparan sulfate highlights the interplay between carbohydrates and protein functions in physiological processes.
Distinction between homopolysaccharides and heteropolysaccharides is crucial in understanding their roles as structural or storage forms in biological systems.### Glycogen Structure and Function
Glycogen has 28 branches, resulting in 29 nonreducing ends and 1 reducing end.
Sugars are added primarily to nonreducing ends, facilitating rapid glucose storage and release.
Glycogen's architecture allows simultaneous enzyme action on multiple branches, enhancing glucose availability.

Amylose vs. Cellulose

Amylose and cellulose are both polysaccharides of D-glucose but differ in linkage types: cellulose with β(1→4), amylose with α(1→4).
Cellulose forms stable, hydrophilic fibers due to hydrogen bonding, while amylose creates helical structures that exclude water.

Cellulose and Glycogen Comparisons

Both consist of D-glucose; however, cellulose has β(1→4) linkages and is linear, while glycogen has α(1→4) linkages and is branched.

D-Glucose vs. D-Fructose

Both sugars are hexoses; glucose is classified as an aldohexose, while fructose is a ketohexose.

Maltose vs. Sucrose

Both are disaccharides; maltose consists of two α(1→4)-linked D-glucose units, while sucrose features α(1→2β)-linked D-glucose and D-fructose.

Hemiacetals and Glycosides

Glycosides are formed when hemiacetals condense with alcohol.
Hemiacetals arise from the condensation of an aldose with alcohol.
Disaccharides contain glycosidic bonds, important for sugar classification.

Fructose and Temperature Effects

Fructose can cyclize, favoring the furanose form at higher temperatures, leading to reduced sweetness in honey and corn syrup when heated.

Anomeric Forms of Sugars

Sucrose has no free anomeric carbon, preventing mutarotation, while lactose exhibits two anomeric forms.

Reducing Sugars

Reducing sugars include N-acetyl-glucosamine, D-lactose, and α-D-glucose due to their ability to donate electrons.

Glycoproteins vs. Proteoglycans

Glycoproteins are located in Golgi complexes, secretory granules, and lysosomes, and contain high-affinity binding sites.
Proteoglycans consist solely of sulfated glycosaminoglycan chains linked to serine and are found at the cell surface and in the extracellular matrix.

Heparin's Role as an Anticoagulant

Heparin binds to antithrombin III, increasing its ability to inhibit coagulation by inducing conformational changes through interactions with positively charged residues.

Additional Terms

Glucosyl: a univalent radical derived from the hemiacetal form of glucose.
Lectin: a protein with high-affinity carbohydrate binding, facilitating cell-cell interactions, often involving oligosaccharides.

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Test your knowledge of carbohydrates with this flashcard quiz focused on definitions and classifications such as disaccharides and oligosaccharides. Discover how these compounds are structured and their significance in biological systems.

Carbohydrates Flashcards Quiz

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Questions and Answers

Which item is NOT associated with disaccharides?

Homopolysaccharides contain a single monomeric sugar species.

What O-glycosidic bond is commonly found in amylose, amylopectin, and glycogen?

A glycogen molecule with 28 branches has how many nonreducing and reducing ends?

Why is it logical for sugars to be added to only one end of glycogen?

Even though amylose and cellulose are made of similar homopolysaccharide chains, they have very different properties. Why?

What structural features do cellulose and glycogen share, and in what ways do they differ?

What structural features do D‑glucose and D‑fructose share, and in what ways do they differ?

What structural features do maltose and sucrose share, and in what ways do they differ?

Select the statements that accurately describe the differences between a hemiacetal and a glycoside.

What chemical property of fructose could account for the decreased sweetness at high temperatures?

Why does sucrose not have any anomeric forms?

Select all of the sugars that are classified as reducing sugars.

Classify each characteristic as describing glycoproteins or proteoglycans.

What amino acid residues of antithrombin III are likely to interact with heparin?

What is glucosyl?

What is a lectin?

A(n) ________ is a(n) ________ with two monosaccharide units.

What chemical feature determines if a sugar is an aldose or a ketose?

Glucose is a monosaccharide with a(n):

Why does (R,S)-aspartame NOT stimulate the sweet receptor?

Which statement is false regarding the enantiomers of glyceraldehyde?

A monosaccharide with a ketone functional group and seven carbons:

What name is given to monosaccharides that differ in configuration about the hemiacetal carbon atom?

Cyclization of monosaccharides:

Using the Fischer projection of D-glucose, identify which statement is true of the Haworth perspective formula of α-D-glucopyranose.

Which reaction is one that is NOT common of glucose?

What term is given to carbohydrates linked by their anomeric carbons?

Even though amylose and cellulose are made of similar homopolysaccharide chains, they have very different properties. Why?

Why are chitin and cellulose hydrophobic and essentially insoluble in an aqueous media?

Polysaccharides:

Which characteristic is NOT one that is true of glycosaminoglycans?

The glycosaminoglycan hyaluronan:

Which statement about glycoconjugates is false?

Which statement about proteoglycans is false?

A laboratory is studying the binding properties of a glycoprotein on the plasma membrane. What amino acids should they analyze for the presence of branched heteropolysaccharides?

Glycoproteins:

Which of these is NOT a glycoconjugate?

Oligosaccharides are:

Glycosaminoglycans?

Types of glycosaminoglycans?

Hyaluronan?

Uronic acid?

Distinctions between hyaluronan and heparan, chondroitin, etc. sulfates?

How does heparan sulfate bind to proteins?

Heparan?

Glycoconjugate?

Proteoglycans?

Glycoprotein?

Glycosphingolipids?

How do glycosaminoglycans connect to proteins?

Two families of membrane heparan sulfate proteoglycans?

GPI anchor?

Antithrombin binds to and inhibits the protease thrombin only in the presence of heparan sulfate.

How does heparan sulfate bind antithrombin?

Proteoglycan aggregates?

Two types of attachments for oligosaccharides in glycoproteins?

Examples of glycoproteins?

Which statement about selectins is false?

Lectins:

The ________ does NOT need to be determined in fully characterizing oligosaccharides and polysaccharides.

Which of these sugars is nonreducing?

Study Notes

Carbohydrates Overview

Monosaccharide Characteristics

Glycosidic Bonds and Nonreducing Sugars

Polysaccharides

Glycosaminoglycans

Glycoproteins and Glycoconjugates

Special Terms and Functions

Sugar Reducing Properties

Summary of Key Functionalities

Amylose vs. Cellulose

Cellulose and Glycogen Comparisons

D-Glucose vs. D-Fructose

Maltose vs. Sucrose

A(n) is a(n) with two monosaccharide units.