Plants are autotrophic organisms meaning they can produce their own chemical energy in contrast to animals that are heterotrophic that obtain energy from other organisms. The process that enables plants to produce their own chemical energy is photosynthesis. Photosynthesis is a process than enables the trapping of light energy and transformation into chemical energy.

Structure of the chloroplast

Composed of an inner and outer membrane. The inner membrane surrounds the stroma and grana (stack of thylakoids). Chlorophyll molecules sit in the surface of each thylakoid and capture light energy from the sun.


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Stages of photosynthesis

Light dependent stage

A stage of photosynthesis that occurs in the grana of the chloroplasts. The light trapped by chlorophyll allowing water to be split into hydrogen and oxygen. Oxygen is released as a byproduct and hydrogen ions are gathered by NADP to form NADPH. This stage produces ATP.

Light independent reaction

This does not require light but does not occur in the dark. This takes place in the stroma of the chloroplast. It requires the input of carbon dioxide and uses hydrogen ions from NADPH and ATP produced in the first stage, to undergo a series of reactions known as the Calvin cycle that ultimately produces glucose.

See also