Pharmacognosy - medicinal plants (herbs)
Pharmacognosy - medicinal plants (herbs)

Theme IV: Photosynthesis

Phases of Photosynthesis

In photosynthesis are two phases:
light reactions
dark reactions

The primary reaction consists in the light absorption of light quanta by a plant´s  specialized molecule that fixes the energy.


The dark reaction are derived from this initial, and where it is not necessary the presence of photons.


In the first one, light intensity is critical to the reaction speed, while in all subsequent ones the temperature is the factor which accelerates these reactions.


The compound for this reaction light is chlorophyll, green pigment found mainly in the leaves of plants that captures light and transforms it into chemical energy through a series of reactions.

 

The different types of chlorophyll and other pigments, called carotenoids and phycobilins absorb wavelengths light something different and transfer energy to chlorophyll A, which ends the process of transformation. These pigments accessories broaden the spectrum of light energy that uses the photosynthesis.

 

The photosynthesis process takes place in cells, in organelles called chloroplasts that contain chlorophyll and other compounds.

to see the equation and general characteristics of photosynthesis go to:
Photosynthesis

From the first compound formed by the reaction of chlorophyll with light, occur a series of phosphorylation reactions, photolysis of water and carbon dioxide fixation. Then the compounds formed are converted by other biochemical reactions to carbohydrates that do not involve light and is called the Calvin process. This process occurs in the stroma of the chloroplast of green leaf plants.

 

The outcome of these reactions is the uptake of carbon dioxide, oxygen production to the enviroment and the biosynthesis of amino acids, fat and starch.

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