BOTANY Higher Secondary Second Year - Textbooks Online

Nonoxidative phase
In this phase, various intermediates such as 3C, 4C, 5C and 7-carbon
phosphorylated sugars are produced. They are phosphoglyceraldehyde
(3C), erythrose phosphate (4C), xylulose phosphate (5C) and sedoheptulose
phosphate (7C).
To summarize, six molecules of glucophosphate enter this pathway.
After oxidation, six molecules of CO2 are released as shown in the step 4
and twelve molecules of NADPH2 are produced as shown in the steps 2
and 4. In other words, after oxidation one molecule of glucose produces
six molecules of CO2 and twelve molecules of NADPH2. Out of six glucose
molecules one is completely oxidized and other five molecules are involved
in the formation of 3C, 4C, 5C, and 7- carbon sugar intermediates. From
these intermediates, five molecules of glucose-6-phosphate are regenerated.
Significance of pentose phosphate pathway
It provides alternative route for carbohydrate breakdown.
It generates NADPH 2 molecules which are used as reductants in
biosynthetic processes. Production of NADPH 2 is not linked to ATP
generation in pentose phosphate pathway.
It provides ribose sugar for the synthesis of nucleic acids.
It provides erythrose phosphate required for the synthesis of aromatic
compounds.
It plays an important role in fixation of CO2 in photosynthesis through
Ru5P.
5.3.5. Anaerobic respiration
Anaerobiosis means life in the absence of oxygen. Certain organisms
can survive in the absence of oxygen. The respiration which takes place in
the absence of free oxygen molecules is called anaerobic respiration. It
occurs in yeast and some bacteria. Hence, they are known as anaerobes.
Glycolysis alone occurs in these organisms. The splitting of glucose into
two molecules of pyruvic acid is given in the following equation.
Glucose Pyruvic acid
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