Q4. Assertion: Photosystem I is so called because it is the first to act in the light reaction. Reason: photosystems are named in the order of their discovery. Is the assertion true? Is the reason true?
The assertion is false: PS II acts first. The reason is true: the photosystems are named in the sequence of their discovery, not of their function (NCERT pages 138 and 140).
Q5. How many molecules of chlorophyll a form the reaction centre of a photosystem, according to NCERT?
One; all the other pigments form the antenna (NCERT page 138).
Q6. List the four events that NCERT includes in the light reaction.
Light absorption, water splitting, oxygen release, and the formation of ATP and NADPH (NCERT page 138).