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Questions and Answers
Carbohydrates can only be classified as monosaccharides based on the number of sugar units.
Carbohydrates can only be classified as monosaccharides based on the number of sugar units.
False
Aldoses are monosaccharides that contain a ketone group.
Aldoses are monosaccharides that contain a ketone group.
False
A trisaccharide is classified as a polysaccharide because it contains three sugar units.
A trisaccharide is classified as a polysaccharide because it contains three sugar units.
False
The general formula for monosaccharides is C_n(H2O)_n.
The general formula for monosaccharides is C_n(H2O)_n.
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A ketotetrose is a monosaccharide that contains four carbon atoms and an aldehyde group.
A ketotetrose is a monosaccharide that contains four carbon atoms and an aldehyde group.
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A substance with an asymmetric carbon atom can only exhibit optical activity.
A substance with an asymmetric carbon atom can only exhibit optical activity.
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The formula for calculating the number of isomers for a substance containing n asymmetric carbon atoms is $2^n$.
The formula for calculating the number of isomers for a substance containing n asymmetric carbon atoms is $2^n$.
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Enantiomers are a type of isomerism that involves compounds with identical spatial configurations.
Enantiomers are a type of isomerism that involves compounds with identical spatial configurations.
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L and D forms of monosaccharides are classified based on the position of the -OH group on the last carbon atom.
L and D forms of monosaccharides are classified based on the position of the -OH group on the last carbon atom.
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Anomers are isomers formed by changing the position of the hydroxyl group on any carbon atom in the monosaccharide.
Anomers are isomers formed by changing the position of the hydroxyl group on any carbon atom in the monosaccharide.
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Glucose is classified as an aldohexose.
Glucose is classified as an aldohexose.
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Dihydroxyacetone is classified as an aldopentose.
Dihydroxyacetone is classified as an aldopentose.
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All monosaccharides are soluble in water.
All monosaccharides are soluble in water.
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Ribulose is a type of aldotetrose.
Ribulose is a type of aldotetrose.
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The ability of a substance to rotate the plane polarized light is known as optical activity.
The ability of a substance to rotate the plane polarized light is known as optical activity.
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Erythrose is a ketose sugar.
Erythrose is a ketose sugar.
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D-galactose is classified as a ketohexose.
D-galactose is classified as a ketohexose.
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Optical activity requires the presence of a chiral center in the molecule.
Optical activity requires the presence of a chiral center in the molecule.
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Study Notes
Carbohydrate Chemistry
- Carbohydrates are aldehyde or ketone derivatives of polyhydric alcohols.
- They serve as a source of energy (e.g., glucose) and structural components in animal and plant cells (e.g., cellulose, chitin).
- Carbohydrates may combine with lipids (glycolipids) or proteins (glycoproteins) and form the ground substance in cell membranes and between tissues.
- Carbohydrates are classified based on the number of sugar units into monosaccharides, disaccharides, oligosaccharides, and polysaccharides.
Monosaccharides
- Monosaccharides are the simplest carbohydrate units.
- They cannot be hydrolyzed into simpler forms.
- Their general formula is C(H₂O)ₙ
- Monosaccharide names end in "-ose."
Monosaccharide Nomenclature
- Aldoses contain an aldehyde group.
- Ketoses contain a ketone group.
Classification of Monosaccharides
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A. Based on the number of carbon atoms:
- Trioses (3 carbons)
- Tetroses (4 carbons)
- Pentoses (5 carbons)
- Hexoses (6 carbons)
- Heptoses (7 carbons)
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B. Based on the functional group:
- Aldoses
- Ketoses
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C. Based on both the functional group and the number of carbons:
- Aldotriose, ketotriose
- Aldotetrose, ketotetrose
- Aldopentose, ketopentose
- Aldohexose, ketohexose
Examples of Monosaccharides
- Aldoses: Glyceraldehyde, Erythrose, Ribose, Glucose, Galactose, Mannose
- Ketoses: Dihydroxyacetone, Xylulose, Ribulose, Fructose
Optical Activity of Monosaccharides
- Optical activity is the ability of a substance to rotate plane-polarized light.
- Monosaccharides exhibit optical activity due to the presence of asymmetric carbon atoms.
- Asymmetric carbon atoms are those bonded to four different groups or atoms.
- Substances containing one asymmetric carbon atom have two isomers
- Substances containing two or more asymmetric carbon atoms can have 2ⁿ isomers, where n is the number of asymmetric carbon atoms.
- Monosaccharides are often classified into D and L isomers based upon the configuration of the asymmetric carbon atom furthest from the carbonyl group.
Monosaccharide Isomerism
-
Enantiomers (L and D forms):
- Monosaccharides exist as pairs of enantiomers, distinguished by the position of the hydroxyl group (-OH) attached to the carbon atom adjacent to the last CH₂OH
- Most monosaccharides found in mammals are of the D- configuration.
Cyclic Forms of Monosaccharides
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Pyranose and Furanose Forms:
- Monosaccharides readily exist in ring forms (pyranose for six-membered rings and furanose for five-membered rings).
- Usually more than 99% of glucose in solution exists in a pyranose form.
-
Anomers:
- Anomers are isomers that differ in the configuration around the anomeric carbon.
- The anomeric carbon is the carbon atom formed from the carbonyl group during ring closure.
- In aldoses, the anomeric carbon is C-1
- In ketoses, the anomeric carbon is C-2
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Description
Test your knowledge on carbohydrate chemistry, focusing on monosaccharides and their classification. This quiz covers the properties, nomenclature, and significance of carbohydrates in biological systems. Perfect for students studying organic chemistry and biochemistry.
