Biochem 7.1 Monosaccharides: Characteristics and Functions
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Questions and Answers

What is the simplest form of carbohydrate known as?

  • Monosaccharides (correct)
  • Oligosaccharides
  • Polysaccharides
  • Disaccharides

Which of the following is a defining characteristic of monosaccharides?

  • Possess a linear structure with no carbonyl group
  • Have a molecular formula of (CH2O)n (correct)
  • Are always larger than three carbon atoms
  • Contain only one hydroxyl group

Which of the following monosaccharides is the most abundant in nature?

  • Glucose (correct)
  • Ribose
  • Fructose
  • Galactose

Which structural feature differentiates the carbonyl group in monosaccharides?

<p>Aldehyde or ketone nature (C)</p> Signup and view all the answers

What role do carbohydrates primarily play in biological systems?

<p>Energy storage and cellular structure (D)</p> Signup and view all the answers

What type of alcohol is present in the structure of monosaccharides?

<p>Both primary and secondary alcohols (A)</p> Signup and view all the answers

Errors in carbohydrate processing can lead to which of the following disorders?

<p>Ehlers-Danlos syndrome (C)</p> Signup and view all the answers

How many carbon atoms does a simple monosaccharide contain at a minimum?

<p>Three (A)</p> Signup and view all the answers

What is the key structural difference between aldoses and ketoses?

<p>Aldoses contain an aldehyde while ketoses contain a ketone. (B)</p> Signup and view all the answers

Which of the following monosaccharides is classified as a ketopentose?

<p>Ribulose (D)</p> Signup and view all the answers

In the context of monosaccharides, which statement regarding the naming of sugars is accurate?

<p>Ketoses typically end with the suffix -ulose. (A)</p> Signup and view all the answers

What defines an aldohexose in the classification of monosaccharides?

<p>A monosaccharide with six carbons and an aldehyde. (D)</p> Signup and view all the answers

Which of the following carbohydrates is NOT classified as an aldose?

<p>Fructose (B)</p> Signup and view all the answers

Which structure represents an aldotriose?

<p>D-Glyceraldehyde (A)</p> Signup and view all the answers

What distinguishes D-sugars from L-sugars?

<p>The configuration of the chiral carbon farthest from the anomeric carbon (D)</p> Signup and view all the answers

Which of the following monosaccharides is categorized as a ketohexose?

<p>D-Fructose (B)</p> Signup and view all the answers

What is a common feature of stereoisomers among monosaccharides?

<p>They have the same molecular formula and functional groups but differ in arrangement (A)</p> Signup and view all the answers

Which carbohydrate has the molecular formula C3H6O3?

<p>D-Glyceraldehyde (C)</p> Signup and view all the answers

Which of the following statements about monosaccharides is incorrect?

<p>Ribose and glucose have the same molecular formula. (B)</p> Signup and view all the answers

In the classification of monosaccharides, what does the prefix 'tri-' indicate?

<p>Three carbon atoms in the structure (A)</p> Signup and view all the answers

Which monosaccharide is an example of an aldopentose?

<p>D-Ribose (B)</p> Signup and view all the answers

What type of isomers are D-glucose and D-mannose classified as?

<p>C2 epimers (D)</p> Signup and view all the answers

Which carbon differs between D-galactose and D-glucose?

<p>Carbon 4 (A)</p> Signup and view all the answers

Which statement about D-galactose and D-mannose is TRUE?

<p>They are diastereomers. (D)</p> Signup and view all the answers

In the Fischer projection of D-ribose, how are the hydroxyl groups oriented?

<p>They all point to the right. (D)</p> Signup and view all the answers

Why are D-galactose and D-mannose not classified as epimers?

<p>They differ at multiple chiral centers. (D)</p> Signup and view all the answers

What is the common classification suffix for monosaccharides?

<p>-ose (A)</p> Signup and view all the answers

Which of the following monosaccharides is classified as a hexose?

<p>Fructose (C)</p> Signup and view all the answers

What is the empirical formula for a monosaccharide?

<p>(CH2O)n (C)</p> Signup and view all the answers

Which of the following classifications describes a monosaccharide with three carbon atoms?

<p>Triose (D)</p> Signup and view all the answers

What distinguishes aldoses from ketoses in monosaccharides?

<p>Position of the anomeric carbon (C)</p> Signup and view all the answers

Which monosaccharide classification includes ribose and ribulose?

<p>Pentose (A)</p> Signup and view all the answers

The anomeric carbon in ketoses is typically found at which carbon position?

<p>2 (A)</p> Signup and view all the answers

What type of enzyme is hexokinase primarily associated with?

<p>Acting on multiple hexoses (B)</p> Signup and view all the answers

What determines whether a monosaccharide is classified as an L-sugar or a D-sugar?

<p>The configuration of the chiral carbon with the highest number (A)</p> Signup and view all the answers

Which statement is true regarding the enantiomers of monosaccharides?

<p>Every chiral center must be flipped to convert D-sugar to L-sugar (A)</p> Signup and view all the answers

What differentiates D-glucose, D-mannose, and D-galactose?

<p>They differ at some but not all stereocenters (D)</p> Signup and view all the answers

In the Fischer projection, where is the hydroxyl group located for a D-sugar?

<p>On the right of the last chiral center (A)</p> Signup and view all the answers

Which monosaccharides are predominantly found in nature as D-isomers?

<p>Monosaccharides (B)</p> Signup and view all the answers

How do L-glucose and D-glucose compare structurally?

<p>They differ at every chiral center (C)</p> Signup and view all the answers

What is true about the chiral carbon content of aldohexoses?

<p>Aldohexoses consist of six carbon atoms and an anomeric carbon at position 1 (A)</p> Signup and view all the answers

What happens when only the last chiral center of D-glucose is flipped?

<p>It forms L-idose (A)</p> Signup and view all the answers

What classification is given to a monosaccharide with five carbons?

<p>Pentose (A)</p> Signup and view all the answers

Which monosaccharide is considered an aldose?

<p>Glucose (B)</p> Signup and view all the answers

How many carbon atoms are found in a hexose?

<p>6 (A)</p> Signup and view all the answers

Where is the anomeric carbon located in a ketose?

<p>Carbon 2 (C)</p> Signup and view all the answers

What defines the classification of trioses in monosaccharides?

<p>They have three carbons. (C)</p> Signup and view all the answers

Which of the following statements is true regarding the molecular formula of monosaccharides?

<p>They can include carbonyl groups and alcohol functional groups. (C)</p> Signup and view all the answers

What is the significance of glucose among monosaccharides in biological systems?

<p>It serves as a primary energy source for living organisms. (D)</p> Signup and view all the answers

Which functional group must at least one carbon in a monosaccharide possess?

<p>A carbonyl group (C=O) (B)</p> Signup and view all the answers

How are the alcohol groups arranged in the structure of monosaccharides?

<p>They can be on primary or secondary carbons within the chain. (C)</p> Signup and view all the answers

Which monosaccharide is characterized by the formula C6H12O6?

<p>Glucose (D)</p> Signup and view all the answers

Flashcards

What are carbohydrates?

A class of molecules consisting of hydrated carbons (carbons combined with water in a 1:1 ratio) that play many important roles in biology.

What are the biological functions of carbohydrates?

Carbohydrates are a source of energy, provide cellular structure, assist in protein folding, and are involved in cell-cell recognition and immune responses.

What are monosaccharides?

The simplest carbohydrates; consist of an uninterrupted carbon chain with one carbonyl carbon and other carbons as alcohols.

What criteria must a molecule meet to be classified as a monosaccharide?

A molecule with at least three carbon atoms, the molecular formula (CH2O)n, a linear carbon chain, one carbonyl carbon, and other carbons as primary or secondary alcohols.

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What is glucose?

The most abundant monosaccharide in nature, with the formula C6H12O6.

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What are the consequences of errors in carbohydrate processing?

Errors in carbohydrate processing can lead to various diseases, including degenerative disorders (like muscular dystrophy) and connective tissue disorders (like Ehlers-Danlos syndrome).

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What is the chemical representation of an alcohol group?

C-OH

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What is the chemical representation of a carbonyl group?

C=O

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How are monosaccharides classified?

Monosaccharides are classified based on the number of carbon atoms they contain.

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What is a triose?

A monosaccharide with three carbon atoms.

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What is a hexose?

A monosaccharide with six carbon atoms.

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What is a pentose?

A monosaccharide with five carbon atoms.

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What is an aldose?

Monosaccharides containing an aldehyde group, such as glucose.

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What is a ketose?

Monosaccharides containing a ketone group, such as fructose.

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What is the anomeric carbon?

The carbon atom in a monosaccharide that has two bonds to oxygen, forming an aldehyde or ketone group.

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Give an example of each type of monosaccharide.

Glucose, fructose, mannose, and galactose are examples of hexoses. Ribose, ribulose, and xylulose are examples of pentoses. Glyceraldehyde and dihydroxyacetone are examples of trioses.

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Aldose

A monosaccharide containing an aldehyde group.

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Ketose

A monosaccharide containing a ketone group.

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Anomeric Carbon

The carbon atom in a monosaccharide that is attached to both an oxygen atom in the carbonyl group (C=O) and an -OH group.

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Aldohexose

A monosaccharide with six carbon atoms and an aldehyde group.

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Ketopentose

A monosaccharide with five carbon atoms and a ketone group.

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How do you determine if a monosaccharide is L or D?

The carbon with the highest number determines whether a monosaccharide is an L or D isomer. If the carbon has an R absolute configuration, it's a D-sugar. If it has an S configuration, it's an L-sugar.

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What are epimers?

Linear monosaccharides with the same basic structure, but differing in their configuration at only one chiral center. They are diastereomers, meaning they are non-superimposable mirror images.

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How to visualize L and D sugars in a Fischer projection?

The D-form of a sugar has its last chiral center's hydroxyl group on the right side in a Fischer projection. The L-form has the hydroxyl group on the left side.

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What are hexoses?

Sugars with six carbons.

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What are pentoses?

Sugars with 5 carbons.

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What are tetroses?

Sugars with 4 carbons.

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What are trioses?

Sugars with 3 carbons.

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Which isomer is more common in nature?

In naturally occurring monosaccharides (sugars), the most common form is the D-isomer.

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Stereoisomers

Monosaccharides that have the same chemical formula but different arrangements of atoms, resulting in variations in their three-dimensional structure.

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L-Sugars and D-Sugars

Monosaccharides classified based on their similarity to L-glyceraldehyde or D-glyceraldehyde, determined by the configuration of the chiral carbon furthest from the anomeric carbon.

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Second-to-last chiral carbon

The second-to-last carbon in a linear monosaccharide chain, used to classify sugars as L or D based on its stereochemistry.

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Different molecular formulas

Monosaccharides with different molecular formulas, like glucose (C6H12O6) and ribose (C5H10O5).

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Constitutional isomers

Monosaccharides with the same molecular formula but different functional groups, like glucose and fructose, both C6H12O6 but with different carbonyl positions.

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Stereoisomers

Monosaccharides with the same molecular formula, same functional groups, but differing only in their stereochemistry (3D arrangement of atoms).

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Anomers

Monosaccharides with the same molecular formula, same functional groups, but differing only in their stereochemistry (3D arrangement of atoms), specifically around the anomeric carbon.

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What is the difference between D-glucose and D-mannose?

D-glucose and D-mannose are C2 epimers, meaning they differ only in the configuration at carbon 2.

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What is the difference between D-glucose and D-galactose?

D-glucose and D-galactose are C4 epimers, meaning they differ only in the configuration at carbon 4.

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How can you remember the structure of D-ribose?

In D-ribose, every hydroxyl group on each chiral center points to the right in a Fischer projection.

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Are D-galactose and D-mannose epimers of each other?

Although D-galactose and D-mannose are both epimers of D-glucose, they are not epimers of each other since they differ at two chiral centers.

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What are stereoisomers?

Monosaccharides with the same molecular formula but different arrangements of atoms, resulting in their 3D structure being different.

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What are L-sugars and D-sugars?

Monosaccharides classified based on their similarity to L-glyceraldehyde or D-glyceraldehyde, determined by the configuration of the chiral carbon furthest from the anomeric carbon.

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Triose

A monosaccharide with three carbon atoms.

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Study Notes

Introduction to Carbohydrates

  • Carbohydrates are hydrated carbons (1:1 ratio of carbon to water)
  • Have various roles in biology, including energy source, cellular structure, protein folding, and cell recognition.
  • Errors in carbohydrate processing can lead to diseases (e.g., muscular dystrophy, Ehlers-Danlos syndrome)

Monosaccharides

  • Simplest carbohydrates
  • Uninterrupted carbon chain
  • One carbon is a carbonyl (aldehyde or ketone)
  • Other carbons are alcohols

Biologically Relevant Monosaccharides

  • Contain at least 3 carbon atoms
  • Have the molecular formula (CH2O)n
  • Exists as a linear chain
  • One carbon is an aldehyde or ketone
  • Other carbons are primary/secondary alcohols

Classification by Number of Carbon Atoms

  • Triose (3 carbons)
  • Tetrose (4 carbons)
  • Pentose (5 carbons)
  • Hexose (6 carbons)
  • Heptose (7 carbons)
  • Octose (8 carbons)
  • Nonose (9 carbons)
  • Decose (10 carbons)

Important Monosaccharides

  • Glucose (C6H12O6) - Most abundant in nature
  • Fructose
  • Mannose
  • Galactose
  • Ribose (C5H10O5)
  • Ribulose
  • Xylulose
  • Glyceraldehyde
  • Dihydroxyacetone (C3H6O3)

Monosaccharide Stereochemistry

  • L-sugars and D-sugars
  • Designated based on the chiral carbon furthest from the anomeric carbon.
  • D-sugars are the predominant form found in nature.
  • Important monosaccharides include D-Ribose, D-ribulose, and D-xylulose

Classification by Cyclization

  • Linear form can cyclize
  • Cyclized into 5- or 6-membered rings
  • Furanose (5-membered ring)
  • Pyranose (6-membered ring)
  • Cyclization can form α or β anomers
  • Anomeric carbon is the carbon that was the carbonyl group, it becomes chiral

Monosaccharide Derivatives

  • Phosphosugars (e.g., glucose-6-phosphate, fructose 1,6-bisphosphate, Uridine diphosphate glucose):
    • Common modification, adding a phosphate group
    • Multiple phosphates may be attached (e.g., bisphosphate, trisphosphate)
  • Deoxysugars (e.g., deoxyribose, a component of DNA):
    • Hydroxyl group is replaced with hydrogen
  • Amino Sugars (e.g., glucosamine, galactosamine, N-acetylglucosamine (GIcNAc), N-acetylgalactosamine (GalNAc), and N-acetylmannosamine (ManNAc)):
    • Hydroxyl group is replaced with amino group (sometimes acetylated)
  • Oxidized Sugars (e.g., glucuronic acid):
    • Carbon atom oxidized to a carboxylic acid; the -ose ending is changed to -uronic acid
  • Reduced Sugars (e.g., sugar alcohols):
    • Aldehyde is reduced to a primary alcohol

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