Textbook Question
Identify a monosaccharide that fits each of the following descriptions:
a. found in high blood levels in diabetes
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20. Carbohydrates
Intro to Carbohydrates
1:53 minutesProblem 31c
Textbook Question
Classify the four carbohydrates (a)–(d) by indicating the nature of the carbonyl group and the number of carbon atoms present. For example, glucose is an aldohexose.
c. 
Verified step by step guidance1
Step 1: Understand the classification of carbohydrates. Carbohydrates are classified based on two main criteria: (1) the type of carbonyl group present (aldehyde or ketone), and (2) the number of carbon atoms in the molecule. For example, an 'aldohexose' is a carbohydrate with an aldehyde group and six carbon atoms.
Step 2: Examine the structure of the carbohydrate provided in the image. Look for the functional group that contains the carbonyl (C=O) group. If the carbonyl group is at the end of the molecule, it is an aldehyde, and the carbohydrate is classified as an 'aldo-'. If the carbonyl group is within the chain, it is a ketone, and the carbohydrate is classified as a 'keto-'.
Step 3: Count the number of carbon atoms in the carbohydrate structure. This will determine the second part of the name. For example, if there are three carbons, it is a 'triose'; if there are six carbons, it is a 'hexose'.
Step 4: Combine the two pieces of information (type of carbonyl group and number of carbons) to classify the carbohydrate. For example, if the molecule has an aldehyde group and six carbons, it is an aldohexose.
Step 5: Repeat the process for each carbohydrate (a)–(d) in the problem. Carefully analyze the structure of each molecule to determine its classification based on the criteria outlined above.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Carbohydrate Classification
Carbohydrates are classified based on the type of carbonyl group they contain and the number of carbon atoms. They can be categorized as aldoses, which have an aldehyde group, or ketoses, which have a ketone group. Additionally, the number of carbon atoms determines whether they are classified as triose (3), tetrose (4), pentose (5), hexose (6), etc.
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Classification of Carbohydrates Example 1
Carbonyl Group
The carbonyl group is a functional group consisting of a carbon atom double-bonded to an oxygen atom (C=O). In carbohydrates, the position of the carbonyl group is crucial for classification: if it is at the end of the carbon chain, the carbohydrate is an aldose; if it is within the chain, it is a ketose. This distinction affects the chemical properties and reactivity of the carbohydrate.
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Structural Representation of Carbohydrates
Carbohydrates can be represented structurally in various forms, including linear and cyclic structures. The linear form shows the arrangement of carbon atoms and functional groups, while the cyclic form, which is more common in solution, illustrates how the carbonyl group reacts with a hydroxyl group to form a ring. Understanding these structures is essential for identifying the type and classification of carbohydrates.
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