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

Photosynthesis as an energy transfer process — practice question

The Hill reaction can be used to investigate the light-dependent stage of photosynthesis in a suspension of isolated chloroplasts. DCPIP may be used to monitor the reaction. DCPIP is a blue dye that becomes colourless when it is reduced by gaining hydrogen and electrons. Oxidised DCPIP (blue) changes to reduced DCPIP (colourless).
(a(i))[2]

The natural hydrogen acceptor in chloroplasts that DCPIP replaces in the Hill reaction is NADP. Reduced NADP is then required in the light independent stage of photosynthesis. State the role of reduced NADP in the light independent stage.

(a(ii))[1]

Predict and explain how the concentration of RuBP in the chloroplasts would change if DCPIP is reduced instead of NADP.

(b)[4]

Explain why tube A is used as the colour standard and why the beaker containing the chloroplast-DCPIP mixture is wrapped in foil.

(c(i))[1]

Fill in Table 2.1 by calculating the rate of the light dependent stage of photosynthesis for the orange wavelength, using the formula: $\text{rate} = \frac{1000}{t}$ where $t$ = time in seconds.

(c(ii))[5]

Using Table 2.1 as evidence, 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: Acts to reduce GP/glycerate-3-phosphate

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