Problem 93 - Chemistry: The Central Science in SI Units, Global Edition

Question

Monosaccharides can be categorized in terms of the number of carbon atoms (pentoses have five carbons and hexoses have six carbons) and according to whether they contain an aldehyde (aldo- prefix, as in aldopentose) or ketone group (keto- prefix, as in ketopentose). Classify glucose and fructose in this way.

Step-by-Step Solution

Answer

In conclusion, glucose and fructose can be categorized as follows: - Glucose: Aldohexose, due to its six carbon atoms and the presence of an aldehyde group. - Fructose: Ketohexose, due to its six carbon atoms and the presence of a ketone group.

Step 1: Glucose Structure

Firstly, let's analyze the structure of glucose. Glucose is an important sugar with the molecular formula C6H12O6. The structure of glucose has six carbon atoms with an aldehyde group (CHO) attached to one of the carbon atoms.

Step 2: Fructose Structure

Now let's analyze the structure of fructose. Fructose is another common sugar with the same molecular formula as glucose, C6H12O6. The structure of fructose has six carbon atoms with a ketone group (C=O) attached to one of the carbon atoms.

Step 3: Classify Glucose

Since glucose has six carbon atoms and contains an aldehyde group, it can be classified as an aldohexose.

Step 4: Classify Fructose

Since fructose has six carbon atoms and contains a ketone group, it can be classified as a ketohexose. In conclusion, glucose and fructose can be categorized as followed: - Glucose: Aldohexose - Fructose: Ketohexose

Key Concepts

Glucose structure

Glucose is one of the most widely recognized monosaccharides. It has the molecular formula \( C_6H_{12}O_6 \). This means glucose consists of six carbon atoms, twelve hydrogen atoms, and six oxygen atoms.
A crucial aspect of glucose's structure is the aldehyde group \((CHO)\) located at the end of its carbon chain. This feature makes glucose an aldohexose. "Aldo" refers to the presence of an aldehyde group, while "hexose" denotes the six carbon atoms in the sugar's structure.
Glucose is vital in biology, serving as a primary energy source for cells. Though its structure might seem simple, understanding it is key to comprehending more complex carbohydrates and metabolic processes.

Fructose structure

Fructose, similar to glucose, shares the same molecular formula \( C_6H_{12}O_6 \); however, its structure is quite different. Instead of an aldehyde group, fructose contains a ketone group \((C=O)\), making its classification distinctive.
The presence of this ketone group near the second carbon atom in the chain classifies fructose as a ketohexose. "Keto" indicates the ketone group presence, and "hexose" indicates the sugar's six carbon atoms.
Fructose is naturally found in various fruits and is known for its sweet flavor. It plays a significant role not only in human diets but also in plant metabolism. Understanding its structure helps in studying its functionality and interaction with other biomolecules.

Aldohexose

An aldohexose is a type of hexose, which means it is a monosaccharide containing six carbon atoms. The defining characteristic of an aldohexose is an aldehyde group \((CHO)\) attached to one of its carbon units, typically at the end of the carbon chain.
Glucose is the most well-known aldohexose and is crucial to many biological processes. It is a building block for polysaccharides like starch and cellulose.
Understanding aldohexoses is essential because they serve as key energy sources and intermediates in metabolism. Their structural characteristics help distinguish them from other sugars, influencing their function and metabolism within organisms.

Ketohexose

Ketohexoses are another kind of hexose monosaccharide characterized by the presence of a ketone group \((C=O)\) instead of an aldehyde group. This ketone group is typically found on the second carbon atom.
Fructose is the most widely recognized ketohexose. The unique arrangement of its atoms allows it to participate in different biochemical processes compared to aldohexoses.
Ketohexoses are not just important as individual sugars; they are vital for the synthesis of more complex carbohydrates. Their distinct structure influences how they are metabolized and utilized for energy, playing crucial roles in various metabolic pathways.