Page 84 - Medicinal Plants_PharmD general

Cellular Respiration

Respiration is the process when plants use up the sugars that were
produced through photosynthesis and turn them into energy. Respiration
uses glucose and oxygen to produce carbon dioxide, water and release
energy (ATP).. The overall process may be written as:

C6H12O6 + 6 O2  6 CO2 + 6 H2O + ATP

Sugar Oxygen Carbon Water Energy

Dioxide

The most common fuel used by the cell is glucose; the way in which
it is metabolized will depend on the availability of oxygen. Thus,
anaerobic respiration (fermentation) does not require oxygen, but as a
result of this process only a small fraction of the chemical energy of
glucose is recovered. On the other hand, in presence of oxygen (aerobic
respiration) glucose is oxidized to CO2 and H2O with a much higher yield
of ATP. Some of the main difference between aerobic and anaerobic
respiration are summarized in the table 2.

Table 2: Aerobic and Anaerobic respiration

Aerobic respiration Anaerobic Respiration

Fermentation

1- Uses molecular O2 Does not use O2

2- Degrades glucose to CO2 + H2O Degrades glucose to lactic acid

or CO2 + alcohol

3- Recovers 50% of chemical energy Less energy 3%

4- Enzymes localized in mitochondria Enzymes localized in cytoplasm

5- Yield 30-32 ATP/glucose mol. Yield 2 ATP/glucose mol.

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