Tetrose

Definition

A tetrose is a monosaccharide, or the simplest type of carbohydrate, that contains four carbon atoms. Tetroses are an important class of carbohydrates that are relevant in the context of classifying carbohydrates and understanding the configurations of aldoses.

5 Must Know Facts For Your Next Test

1. Tetroses are the smallest monosaccharides that can exhibit stereoisomerism, with two possible configurations: D-erythrulose and D-erythrulose.
2. Tetroses are classified as aldoses, meaning they have an aldehyde group (CHO) at the first carbon atom.
3. The configuration of a tetrose is determined by the orientation of the hydroxyl group on the second carbon atom, which can be either above (D-configuration) or below (L-configuration) the plane of the molecule.
4. Enantiomers of tetroses, such as D-erythrulose and L-erythrulose, are non-superimposable mirror images of each other and have different biological properties.
5. Tetroses are important intermediates in various metabolic pathways, including the pentose phosphate pathway and the Calvin cycle in photosynthesis.

Review Questions

• Explain how the classification of tetroses as monosaccharides and aldoses relates to their structural features.
  • As monosaccharides, tetroses are the simplest units of carbohydrates, consisting of a single sugar molecule that cannot be further hydrolyzed. Additionally, tetroses are classified as aldoses because they have an aldehyde group (CHO) at the first carbon atom. This structural feature distinguishes aldoses from ketoses, which have a ketone group (C=O) at the second carbon atom. The presence of the aldehyde group in tetroses is an important characteristic that determines their reactivity and role in various metabolic processes.
• Describe how the configuration of a tetrose, specifically the orientation of the hydroxyl group on the second carbon atom, determines its stereoisomeric form.
  • The configuration of a tetrose is determined by the orientation of the hydroxyl group on the second carbon atom. If the hydroxyl group is positioned above the plane of the molecule, the tetrose is in the D-configuration, while if the hydroxyl group is positioned below the plane, the tetrose is in the L-configuration. This difference in configuration results in the formation of enantiomers, such as D-erythrulose and L-erythrulose, which are non-superimposable mirror images of each other. The specific configuration of a tetrose is an important factor in determining its biological properties and interactions within metabolic pathways.
• Evaluate the significance of tetroses as intermediates in various metabolic pathways, such as the pentose phosphate pathway and the Calvin cycle in photosynthesis, and explain how their structural features contribute to their role in these processes.
  • Tetroses are important intermediates in several key metabolic pathways, including the pentose phosphate pathway and the Calvin cycle in photosynthesis. In the pentose phosphate pathway, tetroses like erythrulose are formed as intermediates in the conversion of glucose-6-phosphate to ribose-5-phosphate, which is essential for the synthesis of nucleic acids. Similarly, in the Calvin cycle, tetroses like erythrulose-4-phosphate are produced as intermediates in the conversion of carbon dioxide to glucose, a crucial process in photosynthesis. The structural features of tetroses, such as their four-carbon backbone and the presence of an aldehyde group, allow them to participate in these metabolic transformations and contribute to the overall energy and carbon cycling within living organisms.

Related terms

Monosaccharide: The most basic unit of carbohydrates, consisting of a single sugar molecule that cannot be hydrolyzed into smaller carbohydrate units.

Aldose: A monosaccharide containing an aldehyde group (CHO) at the first carbon atom.

Epimer: Stereoisomers that differ in configuration at only one chiral carbon atom.