DCPIP is a synthetic hydrogen acceptor used in the Hill reaction. State the natural hydrogen acceptor in chloroplasts that DCPIP replaces in the Hill reaction.
Describe how hydrogen is supplied so that the hydrogen acceptor is reduced during the light dependent stage of photosynthesis.
A suspension of isolated chloroplasts for measuring the rate of the Hill reaction can be made by following these stages: make buffer solution with the same water potential as the chloroplast stroma; homogenise spinach leaves in ice-cold buffer solution; filter the mixture and collect the filtrate; centrifuge the filtrate to produce a chloroplast pellet; transfer the chloroplast pellet into fresh buffer solution in a beaker and stir to form a suspension. Explain why the temperature is kept very low.
Explain why a buffer solution is used.
Explain why a solution with the same water potential as the chloroplast stroma is used.
An experiment was done to find the time needed for DCPIP mixed with a suspension of chloroplasts to decolourise. Table 2.1 shows the results. Complete Table 2.1 by calculating the mean time, for the three replicates, taken for the DCPIP to decolourise.
Calculate the mean rate from the formula $\text{rate} = \frac{1000}{t}$, where $t =$ time in seconds.
The time taken for DCPIP to decolourise was recorded across a range of light intensities. State and explain the expected link between light intensity and the time taken for DCPIP to decolourise.