Biology 9700 · AS & A Level · Photosynthesis as an energy transfer process

Photosynthesis as an energy transfer process — practice question

The light-dependent phase of photosynthesis in a suspension of isolated chloroplasts can be studied through the Hill reaction. Dichlorophenolindophenol (DCPIP) can be used to track the change. DCPIP is a blue dye that turns colourless when it is reduced by taking in hydrogen and electrons. Oxidised DCPIP (blue)  reduced DCPIP (colourless).
(a(i))[2]

The usual hydrogen acceptor in chloroplasts, which DCPIP replaces in the Hill reaction, is NADP. Reduced NADP is then needed in the light independent stage of photosynthesis. State the role of reduced NADP in the light independent stage.

(a(ii))[1]

Predict and explain the effect on the concentration of RuBP in the chloroplasts if DCPIP is reduced in place of NADP.

(b)[4]

Explain the reasons for: the colour standard tube A; covering the beaker containing the chloroplast-DCPIP mixture with foil.

(c)

Table 2.1 presents the experimental results.

(c(i))[1]

Complete Table 2.1 by working out the rate of the light dependent stage of photosynthesis for the orange wavelength, using the formula: rate $= \dfrac{1000}{t}$ where $t$ is the time in seconds.

(c(ii))[5]

Using Table 2.1, describe and explain how light wavelength affects the rate of the light dependent stage of photosynthesis.

Worked solution & mark scheme

This 13-mark question has a full step-by-step worked solution and mark scheme. One marking point: “GP undergoes reduction” …

  • Full mark scheme, point by point
  • Step-by-step worked solution
  • Write your answer & get it marked instantly by AI