Thylacoid membrane

A second potential area to be explored may be biochemical encapsulation of chlorophylls to protect and prolong their stability. New techniques of encapsulation produce a milieu capable of quenching active forms of O2 (radicals and 02) that mimic the protective enviromnent of chlorophylls in the thylacoid membranes. 

Let us start our examination with the prototypical blue protein plastocyanin, found in the thylacoid membrane of chloroplasts, where it acts as an electron carrier in photosynthesis (see Figure 1). As Figure 30 illustrates, the active site of plastocyanin is formed of a Cu(II) ion (pseudo)tetrahedrally coordinated to two histidine nitrogen atoms and... 

Fig. 2.7. Agranal chloroplast from the mesophyll of Cotyledon salmiana. ST, Starch granule PL, Plastoglobulus TM, Thylacoid membranes (electron micrograph by courtesey of...

According to Kreutz enzymes are located between the crystallites. Muhlethaler and other scientists have been able to show that other enzyme systems, the carboxydismutase and an ATPase (an enzyme that controls the equilibrium ATP + HOH ADP -f- P and thus might play a role in photophosphorylation) are located on the outside of the thylacoid membranes. 

The electron microscope permitted a further differentiation. The entire chloroplast is interlaced with a system of self-contained membranes which are called thylacoids ( sack-like ) after the proposal of Menke. The grana consist of thylacoids laid in piles, one on top of the other. Individual thylacoids of such piles also pass through the region outside the grana... 

Surface enlargement All metabolically active structures strive for this and it is achieved here by the arrangement of the membrane systems as thylacoids. 

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