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Notes on the topic on thylakoids?

The stroma has embedded disc-like flattened structures made of double membranes. These discs are called lamellae (thylakoids). The outer surface of the thylakoid is in contact with the stroma and its inner surface encloses an intrathylakoid space. Thylakoids may be stacked like a pile of coins, forming the grana or they may be unstacked called stroma thylakoids.Thus, a granum consists of a series of membrane discs packed back to back, like a stack of coins. However, each disc is interconnected at an angle to all other discs in a granum by tubules called frets. By branching, a fret connects a disc to each of the other discs in turn.

Thylakoids provide a large membrane area to hold the photosynthetic pigments and enzymes. Thylakoids containing chlorophyll (photic apparatus) for photosynthesis, permit separation of the light reactions that occur there from the dark reactions in the chloroplast stroma that fix CO2 to synthesize sugars, starch, fatty acids and some proteins.

ATP and reduced coenzymes diffuse from thylakoids where they are formed into the stroma, where they are used as energy source and reductant respectively, for the fixation of carbon dioxide.


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