Questions and Answers
D-Glucose and L-glucose are
The furanose form of fructose is generated by the formation of a hemiketal, involving the attack of the hydroxyl group on
If the resulting anomeric alcohol group is above the plane of the sugar, the structure is known as
Once formed, the α- and β-forms of D-glucose are
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Why does glucose yield a positive test with cupric ions, such as those found in Fehling's solution, whereas sucrose does not?
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Advanced glycation end products are
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Human blood groups (ABO) are the result of
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The amino acid R groups that serve as the sites for carbohydrate attachment include
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Name the types of carbohydrates you need to determine whether they are monosaccharides, disaccharides, or polysaccharides.
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Classify the sugars as either aldoses or ketoses.
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Classify each monosaccharide according to the position of the carbonyl group and the number of carbon atoms in the molecule.
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Which of the terms explains the relationship between the two compounds?
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Analyze the following pair of compounds. Which of the terms explains the relationship between the two compounds?
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Which structure is a D-2-ketotetrose?
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Draw the Fischer projections of the four aldotetroses.
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Which Haworth projection corresponds to the β-pyranose form of the Fischer projection?
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Select the Fischer projection that is the open chain version of the Haworth projection.
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Name the monosaccharides in the images by placing the appropriate terms.
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Complete the Haworth projection of α-D-galactose by placing labels on the pyranose ring.
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Which of the chair conformations is represented by the Haworth projection?
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Draw the α and β forms of glucose by placing the groups in the appropriate positions.
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Select all the monosaccharides that are correctly paired with their class.
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The specific rotations of the α and β anomers of D-glucose are +112° and +18.7°, respectively. Calculate the proportions of the α and β anomers at equilibrium.
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Which statements about reducing sugars are true?
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Which methods could be used to hydrolyze sucrose to invert sugar nonenzymatically in your kitchen?
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Identify the disaccharide formed when UDP-galactose is combined with another glucose unit.
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Label the Venn diagram for maltose and sucrose.
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Linking together one glucose, one mannose, and one galactose molecule can form how many different trisaccharides?
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Complete the passage about raffinose.
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Determine whether each phrase describes starch, glycogen, or cellulose.
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Why is cellulose not a source of nutrients for humans?
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Label blood types O and A with the correct monosaccharides.
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Which of the structures are examples of glycosaminoglycans?
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___ are the proteins involved in recognition of specific oligosaccharide structures.
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Identify the statement that describes how acarbose and miglitol decrease glucose absorption after a meal.
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Study Notes
Carbohydrates and Their Structures
- D‑Glucose and L‑glucose are classified as enantiomers, sharing the same molecular formula but differing in spatial arrangement.
- The furanose form of fructose arises from a reaction where the hydroxyl group on C‑2 attacks C‑5, creating a hemiketal structure.
- Formation of pyranose and furanose sugar arrangements produces a new chiral center, leading to the α and β forms; the β-anomer has the anomeric alcohol group above the sugar plane.
- α- and β-forms of D‑glucose interconvert via a linear, noncyclic intermediate, maintaining an equilibrium state, rather than converting directly.
- Glucose acts as a reducing sugar with a free aldehyde form, which allows it to react positively with cupric ions, a contrast to non-reducing sucrose.
Glycation and Blood Groups
- Advanced glycation end products result from reactions between reducing sugars and amino groups, impacting protein function.
- Human blood groups (ABO) originate from variations in glycosyltransferases, which modify sugar attachment.
- Glycoprotein structures rely on hydroxyl groups found in R groups for carbohydrate attachment.
Sugar Classification
- Monosaccharides can be classified by their carbonyl group (aldehyde or ketone) and carbon count, with aldoses featuring an aldehyde on C1 and ketoses typically having a ketone on C2.
- Epimers and anomers are specific types of diastereomers distinguished by their configuration at one asymmetric carbon or at the anomeric carbon, respectively.
Chemical Reactions and Properties
- Only certain monosaccharides are reducing sugars, capable of forming carboxylic acids upon oxidation; D‑mannose is a notable example.
- To convert sucrose to invert sugar nonenzymatically, methods include boiling the solution or adding acetic acid in warm water.
Structural Complexity
- A combination of glucose, mannose, and galactose can yield numerous trisaccharides due to structural permutations, amounting to 12,288 potential configurations.
- Raffinose consists of D-galactose, D-glucose, and D-fructose; it is nonreducing due to glycosidic bonds preventing participation in oxidation reactions.
Polysaccharides and Digestibility
- Cellulose is indigestible for humans because vertebrate enzymes hydrolyze α-1,4 linkages, whereas cellulose's β-linkages resist this process; thus, humans lack the enzyme cellulase required for its digestion.
Oligosaccharide Recognition
- Lectins are essential proteins that recognize specific oligosaccharide structures in biological systems, aiding in cell communication and interaction.
Pharmaceutical Applications
- Acarbose and miglitol inhibit glucose absorption by blocking the active site of α-glucosidase, preventing oligosaccharide breakdown in the intestines, which can aid in managing blood sugar levels post-meal.
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Description
Test your knowledge of key concepts from Chapter 10 of Biochemistry with these flashcards. Focus on sugars, their structures, and stereochemistry is essential for understanding biochemical processes. Challenge yourself and see how well you grasp these important definitions.
