Biochemistry Disaccharides and Polysaccharides

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Questions and Answers

What characterizes a methylated sugar?

It can react with oxidizing agents.

It has a free aldehyde group.

It is a reducing sugar.

It cannot achieve the open-chain form. (correct)

Which of the following is true about deoxysugars?

They lack a hydroxyl group at one of their carbons. (correct)

They contain additional hydroxyl groups.

They are non-essential for DNA structure.

They are reducing sugars.

What type of bond connects monosaccharides in disaccharides?

Alpha-1,4-glycosidic bond (correct)

Amino bond

Beta-1,6-glycosidic bond

N-glycosidic bond

Which sugar alcohol is mentioned as a commercial sweetener?

Sorbitol Signup and view all the answers

What distinguishes sugar acids from other types of sugars?

They contain at least one carboxyl group. Signup and view all the answers

In the context of nucleic acids, what is an N-glycosidic bond?

A bond linking an organic base to the anomeric group of a sugar Signup and view all the answers

What is true about phosphorylated sugar derivatives?

They function as intermediates in biochemical pathways. Signup and view all the answers

Which description applies to the α-1,4-glycosidic bond in maltose?

It links the 1 carbon of one glucose to the 4 carbon of another glucose. Signup and view all the answers

Which of the following disaccharides is considered a non-reducing sugar?

Sucrose Signup and view all the answers

What type of linkage is present in lactose?

β-1,4 linkage Signup and view all the answers

Which glycosidic linkage is responsible for the branch points in glycogen?

α-1,6 linkage Signup and view all the answers

What type of structure does cellulose form due to its linkages?

Sheet-like structure Signup and view all the answers

Which of the following sugars is composed of two glucose units?

Maltose Signup and view all the answers

Which component of carbohydrates is responsible for the synthesis of carbohydrate polymers?

Glycotransferases Signup and view all the answers

Why is cellulose indigestible by humans?

Humans lack the enzyme to hydrolyze β-1,4 linkages Signup and view all the answers

Which of the following describes amino sugars?

They contain an amino group substituting for a hydroxyl Signup and view all the answers

What is mutarotation?

The interconversion of α- and β-anomers through an open chain form. Signup and view all the answers

What forms when a hemiacetal reacts with a second alcohol molecule?

An acetal Signup and view all the answers

Which type of sugar can undergo mutarotation?

Both aldoses and ketoses Signup and view all the answers

What is the structural feature of ketoses?

They have the carbonyl carbon at the #2 position. Signup and view all the answers

How are reducing sugars identified?

Through the reaction with Fehling's reagent. Signup and view all the answers

What happens to a monosaccharide when its anomeric hydroxyl group is methylated?

It becomes a non-reducing sugar. Signup and view all the answers

Which of the following cyclic forms can fructose adopt?

A five-membered furanose and a six-membered pyranose ring. Signup and view all the answers

What stabilizes the cyclic structure of monosaccharides?

The energy levels of the cyclic structures. Signup and view all the answers

What is the general empirical formula for most carbohydrates?

[CH2O]n Signup and view all the answers

Which term is used to describe monosaccharides that contain an aldehyde functional group?

Aldose Signup and view all the answers

What is the maximum number of monosaccharide units that a polysaccharide can have?

1000 or more Signup and view all the answers

What are isomers that are exact mirror images of each other called?

Enantiomers Signup and view all the answers

Which of the following statements about monosaccharides is FALSE?

They can only contain aldehyde functional groups. Signup and view all the answers

What is a common example of an oligosaccharide consisting of three monosaccharide units?

Raffinose Signup and view all the answers

Which carbohydrate is classified as an aldohexose?

Glucose Signup and view all the answers

What occurs during the process of mutarotation in monosaccharides?

Conversion of α- and β-anomers via an open chain form Signup and view all the answers

What role do chiral centers play in carbohydrates?

They create enantiomers that rotate polarized light. Signup and view all the answers

Which statement accurately describes the cyclization of aldoses?

Involves reaction between an alcohol and aldehyde within the same molecule Signup and view all the answers

What determines the distribution of cyclic structures in fructose?

Relative energy levels of the various structures Signup and view all the answers

What is the result when a hemiacetal is formed from a monosaccharide?

Creation of a cyclic version of the sugar Signup and view all the answers

Which type of sugar cannot undergo mutarotation?

Ketose locked in an acetal structure Signup and view all the answers

What forms when two cyclized carbohydrates react?

An acetal Signup and view all the answers

What structural feature distinguishes ketoses from aldoses?

Carbonyl carbon located at the #2 position Signup and view all the answers

How are most monosaccharides classified in terms of reducing capability?

Most are reducing compounds unless modified Signup and view all the answers

What is the term for a mixture consisting of equal amounts of two enantiomers?

Racemic mixture Signup and view all the answers

How many total isomers does an aldohexose have based on the number of its chiral centers?

16 Signup and view all the answers

Which of the following best describes epimers?

They differ in stereochemistry at only one chiral carbon. Signup and view all the answers

What does configuration refer to in the context of stereochemistry?

The spatial arrangement of groups around a chiral center. Signup and view all the answers

Which prefix is used to denote the configuration of aldotrioses based on their chiral centers?

D- or L- Signup and view all the answers

What is the maximum number of isomers possible for aldotetroses?

4 Signup and view all the answers

What is the main distinction between configurations and conformations?

Configurations are static while conformations are dynamic. Signup and view all the answers

How many centers of asymmetry does an aldotriose possess?

1 Signup and view all the answers

Which disaccharide contains a β-1-4 linkage?

Lactose Signup and view all the answers

What type of sugar is sucrose classified as?

Non-reducing sugar Signup and view all the answers

Which component of glycogen is responsible for its branching structure?

α-1,6 linkages Signup and view all the answers

Which statement is true about maltose?

It consists of two glucose units connected by an α-1-4 linkage. Signup and view all the answers

Why is cellulose indigestible by humans?

Humans lack the enzyme to hydrolyze β-1,4 linkages. Signup and view all the answers

Which of the following is a component of proteoglycans and glycoproteins?

Amino sugars Signup and view all the answers

What type of linkage primarily makes up starch and glycogen?

α-1,4 linkages Signup and view all the answers

Which of the following best describes the formation of carbohydrate polymers?

Utilizes nucleotide sugars and glycotransferases Signup and view all the answers

Which sugar is specifically mentioned as lacking a hydroxyl group at carbon 2?

2-deoxy-ribose Signup and view all the answers

What common structural feature distinguishes sugar acids from other sugars?

Presence of a carboxyl group Signup and view all the answers

What type of biochemical pathway do phosphorylated sugar derivatives generally participate in?

Glycolysis Signup and view all the answers

Which compound is identified as a sugar alcohol and also serves as a component of biological structures?

Inositol Signup and view all the answers

What characterizes a N-glycosidic bond in nucleic acids?

Attachment of a nitrogen atom to the anomeric group of a sugar Signup and view all the answers

Which of the following sugars contains a free aldehyde group and can thus undergo oxidation?

Reducing sugar Signup and view all the answers

In maltose, which type of glycosidic bond joins the two glucopyranose units?

Alpha-1,4-glycosidic bond Signup and view all the answers

What structural characteristic makes methylated sugars non-reducing?

Inability to achieve an open chain form Signup and view all the answers

Why are methylated sugars classified as non-reducing?

They lack a free aldehyde group. Signup and view all the answers

What characterizes a sugar phosphate?

It has a covalently bound phosphate group. Signup and view all the answers

Which of the following statements is true about sugar acids?

They contain at least one carboxyl group. Signup and view all the answers

What is a significant feature of sugar alcohols?

They replace an aldehyde or ketone group with a hydroxy group. Signup and view all the answers

What defines a 2-deoxy-ribose sugar?

It lacks a hydroxyl group at carbon 2. Signup and view all the answers

How are N-glycosidic bonds formed?

By the covalent linking of a nitrogen atom to an anomeric carbon of ribose or deoxy-ribose. Signup and view all the answers

What distinguishes an α-1,4-glycosidic bond in carbohydrates?

It involves a downward radiating linkage from one carbon to another. Signup and view all the answers

Which carbohydrate component serves as a structural element in connective tissues?

Sugar acids Signup and view all the answers

What designates the anomeric position in a cyclic form of fructose?

The new hydroxyl group produced during cyclization Signup and view all the answers

Which conformation of aldohexoses tends to predominantly minimize steric hindrance?

Chair form with equatorial positions Signup and view all the answers

What happens to the cyclic forms of carbohydrates when methylated at the anomeric hydroxyl?

They lock into either α− or β− form Signup and view all the answers

How do bulky groups in a carbohydrate molecule influence its conformation?

They create instability when in close proximity Signup and view all the answers

Which disaccharide is classified as a reducing sugar because of its ability to mutarotate?

Both B and C Signup and view all the answers

What are the two main forms of glucose conformation?

Chair and boat Signup and view all the answers

What type of linkage primarily characterizes the branched structure of glycogen?

α-1,6 linkages Signup and view all the answers

Which of the following statements correctly describes cellulose compared to starch and glycogen?

Cellulose has a sheet-like structure due to β-1,4 linkages. Signup and view all the answers

Which of the following statements about steric hindrance is correct?

Steric hindrance can lead to certain conformations being impossible Signup and view all the answers

What characterizes a racemic mixture in stereochemistry?

It contains equal amounts of two enantiomers that cancel out their optical activity. Signup and view all the answers

What differentiates maltose from other common disaccharides in terms of its composition?

It consists of two glucose units bonded by an α-1,4 linkage. Signup and view all the answers

When considering the cyclic forms of fructose, which describes its pyranose form?

It is a six-membered ring structure Signup and view all the answers

How many possible isomers can an aldohexose have?

16 Signup and view all the answers

What defines an epimer?

It is a monosaccharide differing in stereochemistry at only one chiral carbon. Signup and view all the answers

Which compound serves as a common component in both glycoproteins and proteoglycans?

N-acetyl derivatives of glucose Signup and view all the answers

What factors determine the preferred conformation of carbohydrates?

The energy levels and steric hindrance present Signup and view all the answers

What distinguishes conformation from configuration?

Configuration is fixed and does not change with rotation about single bonds, whereas conformation does. Signup and view all the answers

Which property distinguishes sucrose from lactose and maltose?

It does not contain a reducing sugar structure. Signup and view all the answers

In the context of aldotrioses, what does the prefix D- or L- indicate?

The position of the hydroxyl group on the highest-numbered chiral carbon. Signup and view all the answers

Which type of enzyme is responsible for synthesizing carbohydrate polymers?

Glycotransferase Signup and view all the answers

What characteristic of chondroitin 6-sulfate is critical for its function in Glycosaminoglycans?

Negatively charged sulfate components Signup and view all the answers

What is the total number of isomers for aldotetroses?

4 Signup and view all the answers

Which statement about the centers of asymmetry in aldohexoses is correct?

Only the middle four carbons can be chiral centers. Signup and view all the answers

Which of the following is NOT a characteristic of epimers?

They are mirror images of each other. Signup and view all the answers

What designates a sugar as 'D' in its configuration?

The –OH group is located on the right in the lowest center of asymmetry. Signup and view all the answers

How many total isomers can aldohexoses form?

8 Signup and view all the answers

What occurs at the anomeric carbon when a cyclic monosaccharide is formed?

It becomes a new hydroxyl group with chirality. Signup and view all the answers

Which of the following statements about α- and β-anomers is true?

They differ only at the new asymmetric center formed during cyclic formation. Signup and view all the answers

In the conversion from the Fischer formula to the Haworth formula, how do the hydroxyl groups at carbons 2 and 4 change position?

They radiate down when they were originally to the right. Signup and view all the answers

What is true about the hydroxymethyl group in D-aldohexoses according to the cyclic structure?

It radiates up in the cyclic structure. Signup and view all the answers

What characterizes the process of mutarotation in D-glucose?

It is the conversion between cyclic forms without breaking glycosidic bonds. Signup and view all the answers

What distinguishes D-isomers of sugars from L-isomers?

The configuration of the hydroxyl group at the lowest center of asymmetry. Signup and view all the answers

Study Notes

Common Disaccharides

Sucrose is a non-reducing sugar.
Sucrose is commonly used in a bag purchased from the store as "sugar".
Sucrose is made up of glucose and fructose linked by an α-1, β-2 glycosidic bond.
Lactose is a reducing sugar found in mammalian milk.
Lactose is a disaccharide made up of galactose and glucose in a β-1, 4- linkage.
Maltose is a reducing sugar.
Maltose is made up of two glucose units linked by an α-1, 4 glycosidic bond.
Maltose is found in glycogen and starch.

Glycogen

Glycogen is a storage polysaccharide.
Approximately 90% of Glycogen is made up of α-1, 4 linkages.
Approximately 10% of Glycogen is made up of α-1, 6 linkages.
α-1, 6 linkages create branch points in Glycogen.

Cellulose

Cellulose is a structural plant polysaccharide.
Cellulose has β-1, 4 linkages.
Cellulose forms a sheet-like structure.
Cellulose is indigestible by humans as there is no appropriate enzyme in the body to break down β-1, 4-linked glucose units.
Starch and Glycogen contain α-1, 4 linkages for digestible structures.

Amino Sugars

Amino sugars are common components of proteoglycans and glycoproteins.
Amino sugars are formed when a hydroxyl group is replaced with an amino group.
N-acetyl derivatives of glucose and galactose are some of the most common components of proteoglycans and glycoproteins.

Acidic Disaccharides

Acidic Disaccharides are common components of Glycosaminoglycans.
Acidic Disaccharides contain carboxylate and sulfate components.

Nucleotide Sugars

The synthesis of carbohydrate polymers is catalyzed by enzymes called glycotransferases.
Nucleotide sugars are used to create carbohydrate polymers.
The cleavage of phosphoester linkages drives polysaccharide synthesis.

Methylated Sugars

Methylated sugars become non-reducing because they cannot achieve the open chain form.
Methylated sugars do not react with oxidizing agents as these reactions require a free aldehyde group.

Deoxysugars

Deoxysugars lack a hydroxyl group at one of their carbons.
Ribose and deoxyribose are essential components of RNA and DNA.
2-deoxyribose is a prominent example of a deoxysugar due to its lack of the hydroxyl group at carbon 2.

Sugar Phosphates

Sugar phosphates have at least one covalently bonded phosphate residue.
Sugar phosphates are generally found within cells and serve as intracellular intermediates in biochemical pathways.

Sugar Acids

Sugar acids contain at least one carboxyl group.
Galacturonic acid is a common sugar acid.
Sugar acids are commonly found in complex carbohydrate polymers that are responsible for structure in connective tissue and other extracellular polysaccharides.

Sugar Alcohols

Sugar alcohols have a hydroxyl group in place of the aldehyde or ketone functional group.
Sorbitol is a common sugar alcohol.
Inositol is a cyclic polyalcohol that is a component of phosphoglycerols.
Inositol can act as a biological second messenger when in a phosphorylated state.

N-Glyosidic Bonds

N-Glycosidic bonds are formed when the nitrogen atom of a purine or pyrimidine base is covalently linked to the anomeric group of ribose or deoxyribose.
N-Glycosidic bonds are present in nucleic acids and nucleotides.

α-1, 4-Glycosidic Bond

α-1, 4-Glycosidic Bonds are a key part of disaccharides, oligosaccharides, and polysaccharides.
Maltose contains two glucopyranose units linked by α-1, 4-glycosidic bonds.
The α-1, 4-glycosidic bond is created when the 1 (anomeric) carbon of the glucose unit on the left is connected to the 4 carbon of the glucose unit on the right.
The linkage from the anomeric carbon radiates downward, creating an α-linkage.

Mutarotation

Mutarotation is the conversion of α- and β-anomers through the formation of an open chain form.
Monosaccharides in the open chain form are constantly equilibrating with α- and β-anomers in solution.

Hemiacetal Formation

Hemiacetal formation occurs where an aldose, like glucose, forms a cyclic structure when an alcohol group reacts with an aldehyde group in the same molecule.

Hemiketal Formation

Hemiketal formation occurs when a ketose, like fructose, forms a cyclic structure by the reaction of an alcohol group with a ketone group in the same molecule.

Acetal Formation

Acetal formation is the result of a hemiacetal reacting with a second alcohol molecule.
When two cyclized carbohydrates react to create a disaccharide, this is equivalent to the formation of an acetal.
Acetal derivatives are generally stable in comparison to hemiacetals.

Reducing and Non-Reducing Sugars

Fehling’s reagent is a classic test to identify carbohydrates that can mutarotate through an open chain form to produce an aldehyde.
Open chain aldehydes can reduce Cu2+ and are oxidized to a carboxylic acid.
Most monosaccharides are reducing compounds, but they can become non-reducing compounds if the anomeric hydroxyl group is methylated or trapped in an acetal structure.

Ketoses

Ketoses have the carbonyl carbon at the #2 position of the monosaccharide.
They have one less asymmetric center compared to the equivalent aldose molecule.
Fructose is an example of a ketose commonly consumed daily.

Mutarotation of Fructose

Fructose's ability to mutarotate leads to the formation of cyclic derivatives.
Fructose can cyclize to form a five-membered furanose ring (α-D-fructofuranose) anomer.
Fructose can also cyclize to form a six-membered pyranose ring.
The proportions of open chain form and cyclic forms of fructose depend on the relative energies of those structures.
The structure with the lowest energy level will have the highest concentration at equilibrium.

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Description

Explore the world of disaccharides and polysaccharides with this quiz. Learn about common sugars like sucrose, lactose, and maltose, as well as their structures and functions. Test your understanding of glycogen and cellulose as crucial components in biological systems.