Sugars as Energy Sources

Metabolically the main monosaccharide useful for the production of energy is glucose. During the glycolysis process glucose is enzymatically transformed and degraded to piruvate and is a preamble which is further introduced into the Krebs cycle.

CH2OPO32-

C-OH

C-OH HC-OH

CH2OPO32-RuBP

Enediol form

RuBP Carboxylase

O CH2OPO32-

CH2OPO3

CH2OPO HC-OH

O OH

ch2opo3

3-PGA

ADP +Pi

C-OPO3 CH-OH

ch2opo;

NADPH NADP+

CH2OPO32-RuBP

Figure 1.17. Carbohydrate synthesis from CO2 fixation.

Carbohydrates are responsible of several biological events mainly related with the storage and production of energy, as metabolic intermediates and signal molecules. They are also constitutive structural units of essential biomolecules such as polysaccharides (starch, glucogen, and cellulose), glycoproteins, glycol-ipids, and nucleotides. The process by which glucose is used as energy source, to produce ATP and pyruvate is known as glycolysis and consist in series of events represented in Figure 1.18.

The second cycle of glycolysis is divided in four steps.

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