Plant Physiology - Lecture Notes - O. M. Tarnopilska 2019

5. Plant Respiration
5.2 Stage I of Respiration. Glycolysis

The Glycolytic Pathway of respiratory METABOLISM consists of two phases: anaerobic (Glycolysis) and aerobic (the Krebs cycle).

Glycolysis reactions take place in the Cytoplasm and Chloroplasts. As a result of glycolysis, one glucose molecule yields two molecules of pyruvic acid and four ATP molecules (Fig. 5.1).

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Figure 5.1 - Stages of glycolysis (dashed lines indicate bypass pathways during

the reversal of glycolysis (after V. V. Polovyi))

Since the high-energy bond is formed directly on the oxidation substrate, this process of ATP generation is known as substrate-level phosphorylation. Two ATP molecules cover the energy cost of

initial substrate activation via phosphorylation. Thus, a net gain of two ATP molecules is accumulated. In addition, during the

glycolytic process, two NAD molecules are reduced to NADH, The oxidation of which in the

Mitochondrial Electron Transport chain leads to the synthesis of six ATP molecules. This results in a total of eight ATP molecules produced. The resulting two pyruvic acid molecules enter the aerobic phase of Respiration.

Functions of glycolysis in The Cell:

·links respiratory substrates with the Krebs cycle;

·supplies the cell with ATP and NADH to meet its energy demands;

·produces intermediates required for cellular synthetic processes.