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Biology 2nd Baccalaureate

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2.3.2. Tetroses


They are carbohydrates made up of chains of four carbon atoms. They can be aldotetrose, with the aldehyde group on the first carbon, or ketotetrose, with the ketone group on the second carbon. Therefore, there are:

  • Two aldotetrosas, the treosa and the erythrosa.
  • ketotetroseerythrulose. The ending -ulose is common in ketotetrosses and ketopentoses.

In aldotetrosas there are two asymmetric carbonsAs in the rest of the monosaccharides, the D or L configuration is determined taking as a reference the asymmetric carbon furthest from the carbonyl group, which in the aldotetrose is carbon 3.

As has been said, two carbohydrates are called epimers that only differ in the position of the hydroxyl group (OH) of an asymmetric carbon. Thus, for example, L-erythrose and L-treose are epimers. They are different substances and, therefore, with different properties.

Ketotetrosses have only one asymmetric carbon, and it is located at carbon 3.


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