In: Biology
With respect to PSII activity, what is the difference between specific activity and total activity ?
PSII is photosystems II which are present in thylakoid membrane which drag photons from light for photosynthesis.Activity of photosystems can be measured in vitro using DCPIP assay.DCPIP is a redox indicator; each molecule is reduced by accepting two electrons and two hydrogen ions.Within the thylakoid membranes of chloroplasts it accepts electrons and hydrogen ions from plastoquinone, one of the components of the chloroplastic electron transfer chain,thus reducing DCPIP. Since DCPIP can also be reduced by high-energy electrons from other sources, it is necessary for the calculations that give a measure of photosynthetic activity to be based on the changes in absorbance between the illuminated samples and those kept in the dark.
SO specific activity can be stated as micromoles of DCPIP reduced per ml of sample per hour and the total activity (amount of oxygen produced) in each sample can now be derived by multiplying the activity per ml by the total volume of the fraction..