Chloroplasts function

The proton motive force (pmf) is essential for both mitochondrial and chloroplast function. What produces the pmf, and what is its relationship to ATP ... 

On the other hand, the evidence ha vs gradually been accumulated indicating that IE like photosynthetic carbon reduction is closely connected with chloroplast functioning (1, 4-6, 14-16), and in 1982 it was shown that isolated poplar chloroplasts are capable of isoprene photobiosynthesis (17). 

These observations, taken together, suggest that the major site of ozone damage is extra-chloroplastic and the observed effects of ozone on chloroplast function may be an indirect phenomenon ... 

In WiUstatter s mechanism, this would have required that chlorophyll was constantly associated with carbon anhydride otherwise the short lifetime of exited state would have caused a large loss. Traces of formaldehyde were detected from illuminated leaves, but a relation with oxygen developed was not demonstrated, and at any rate the process occurring in chloroplast was not duplicated in solution, suggesting a role of something more complex than a single molecule of chlorophyll in chloroplasts function. 

Fig. 5.15. The dependence of the magnitude on the reversible light-induced decrease of the high field component of the EPR signal from spin label on TEMPOamine concentration in the suspension of bean chloroplasts functioning under conditions of cyclic electron transport mediated by phenasine metosulphate, photosystem 2 was inhibited by diuron (after [70]).

The results of the measurements of the ApH (external pH 8.0) with the spin label TA under various conditions of chloroplast functioning are summarized in Table 5.1 [70, 82]. 

If there is uniform distribution of the intravesicular pH over all compartments of the system, both methods would of course give the same results. This is probably the case for chloroplasts functioning in state 4. However, if there are compartments with different values of the internal pH (nonuniform distribution), the local and averaging methods could lead to quite different results (see, e.g., an example in Section 3.2.2). 

Fig. 5.17. The time-course of the light-induced pH changes in the suspension of bean chloroplasts functioning under cyclic (A) or noncyclic (B) electron transport conditions.

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