Podcast
Questions and Answers
What structural feature distinguishes an aldose from a ketose?
What structural feature distinguishes an aldose from a ketose?
- The presence of a hydroxyl group on the penultimate carbon.
- The total number of carbon atoms.
- The presence of a chiral center.
- The location of the carbonyl group; aldoses have it at the end of the carbon chain, ketoses have it internally. (correct)
Which of the following is an example of a hexose?
Which of the following is an example of a hexose?
- Glucose (correct)
- Ribose
- Erythrose
- Glyceraldehyde
What is the structural basis for designating a sugar as D or L?
What is the structural basis for designating a sugar as D or L?
- The direction in which it rotates plane-polarized light.
- The configuration of the hydroxyl group on the chiral center farthest from the carbonyl group. (correct)
- The specific arrangement of all hydroxyl groups in the Fischer projection.
- The total number of chiral centers in the molecule.
What term describes the relationship between D-glucose and L-glucose?
What term describes the relationship between D-glucose and L-glucose?
What distinguishes diastereomers from enantiomers?
What distinguishes diastereomers from enantiomers?
If two sugars are epimers, what structural characteristic defines their relationship?
If two sugars are epimers, what structural characteristic defines their relationship?
Which of the following pairs of sugars are diastereomers?
Which of the following pairs of sugars are diastereomers?
What is the relationship between D-glucose and D-galactose?
What is the relationship between D-glucose and D-galactose?
Which term best describes glyceraldehyde, based on its number of carbon atoms?
Which term best describes glyceraldehyde, based on its number of carbon atoms?
If a sugar is designated as an aldohexose, what does this indicate about its structure?
If a sugar is designated as an aldohexose, what does this indicate about its structure?
Which carbon determines whether a monosaccharide is D or L when multiple chiral centers are present?
Which carbon determines whether a monosaccharide is D or L when multiple chiral centers are present?
What is the defining characteristic of enantiomers?
What is the defining characteristic of enantiomers?
How many stereoisomers are possible for an aldose with four asymmetric centers?
How many stereoisomers are possible for an aldose with four asymmetric centers?
If you have D-ribose, what is its enantiomer?
If you have D-ribose, what is its enantiomer?
Two sugars have the same molecular formula but differ in their structural formula. Which term accurately describes this relationship?
Two sugars have the same molecular formula but differ in their structural formula. Which term accurately describes this relationship?
Which statement correctly describes the relationship between D-erythrose and D-threose, given that they are both four-carbon aldoses?
Which statement correctly describes the relationship between D-erythrose and D-threose, given that they are both four-carbon aldoses?
A biochemist discovers a new sugar with 7 carbons and a ketone group at carbon 2. How should this sugar be classified?
A biochemist discovers a new sugar with 7 carbons and a ketone group at carbon 2. How should this sugar be classified?
Compound X is the mirror image of D-mannose but is not superimposable upon it. What is Compound X?
Compound X is the mirror image of D-mannose but is not superimposable upon it. What is Compound X?
Suppose a previously unknown aldose is found to have 5 carbons, with the hydroxyl group on the penultimate carbon oriented to the left in its Fisher projection. How would this sugar be named?
Suppose a previously unknown aldose is found to have 5 carbons, with the hydroxyl group on the penultimate carbon oriented to the left in its Fisher projection. How would this sugar be named?
A researcher synthesizes a novel sugar molecule. Upon analysis, it is determined to be a ketose with 8 carbon atoms, and it exhibits optical activity. Furthermore, it is observed to mutarotate in solution. Considering these characteristics, which of the following classifications is MOST accurate for this molecule?
A researcher synthesizes a novel sugar molecule. Upon analysis, it is determined to be a ketose with 8 carbon atoms, and it exhibits optical activity. Furthermore, it is observed to mutarotate in solution. Considering these characteristics, which of the following classifications is MOST accurate for this molecule?
Flashcards
What is an aldose?
What is an aldose?
A sugar with an aldehyde group.
What is a ketose?
What is a ketose?
A sugar with a ketone group.
What is a triose?
What is a triose?
A three-carbon sugar.
What is a tetrose?
What is a tetrose?
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What is a pentose?
What is a pentose?
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What is a hexose?
What is a hexose?
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What are enantiomers?
What are enantiomers?
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What are diastereomers?
What are diastereomers?
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What is an epimer?
What is an epimer?
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Study Notes
- Common sugars have specific nomenclature to describe their properties.
Aldose vs. Ketose
- Glucose and fructose are two common sugars with identical structures in their lower four carbons, including a CH2OH termination.
- Glucose terminates in an aldehyde group.
- Fructose has a ketone group on carbon number two.
- Glucose is an aldose (aldehyde sugar).
- Fructose is a ketose (ketose sugar).
- Sugars are indicated by the letters "OSE" at the end of their name
Sugar Sizes
- Glyceraldehyde has three carbons and is a triose.
- A sugar with four carbons is a tetrose.
- Ribose, found in nucleotides, has five carbons and is a pentose.
- Glucose has six carbons and is a hexose.
- Glucose can be described as an aldohexose.
Stereochemistry
- Carbons attached to four different atoms can have two different spatial arrangements.
- In glyceraldehyde, the L-configuration is when the hydroxide is on the left.
- The D-configuration is when the hydroxide is on the right.
- Larger sugars with multiple asymmetric centers are designated D or L based on the bottom carbon in the linear form.
- D and L glyceraldehyde are mirror images of each other.
Multiple Asymmetric Centers
- Glucose has four asymmetric centers.
- Different configurations at these centers result in different sugars, named individually, not by stereochemistry
- An aldose with four asymmetric centers can have 16 different names.
- D-glucose has the hydroxide on the right side of the bottom carbon.
- L-glucose is the mirror image of D-glucose, with every hydroxide flipped.
- Enantiomers are sugars that are mirror images of each other.
- Every D sugar has an L sugar as its mirror image.
- D-glucose's enantiomer is L-glucose, and D-glyceraldehyde's enantiomer is L-glyceraldehyde.
Diastereomers
- Diastereomers are sugars with different configurations but the same basic chemistry, not mirror images.
- D-glucose and D-gulose are both aldoses.
- Hydroxides at carbon number two and the bottom of D-glucose and D-gulose are on the same side
- The configurations at carbons three and four are different, making them diastereomers
Epimers
- Epimers are diastereomers that differ in configuration at only one carbon.
- D-glucose and D-galactose have identical structures except for one carbon.
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