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

Photosynthesis as an energy transfer process — practice question

Fig. 5.1 presents the seaweed Laminaria hyperborea. It is a photosynthetic protoctist that lives in coastal waters near Norway. This seaweed is cultivated commercially so that the glucose polysaccharide alginate can be extracted. Alginate is incorporated into some food products. Rising atmospheric carbon dioxide has led to greater carbon dioxide levels in the ocean. As a result, ocean pH has fallen, causing ocean acidification. Scientists are investigating seaweeds such as L. hyperborea because photosynthesis in these organisms removes large amounts of carbon dioxide. In theory, this could raise ocean pH and help to reverse ocean acidification.
(a(i))[1]

State where light energy is absorbed in the chloroplasts of L. hyperborea.

(a(ii))[1]

Name one product from the light-dependent stage of photosynthesis.

(a(iii))[4]

Outline the reactions in the stroma that result in the formation of a polysaccharide, such as alginate. The first sentence has already been completed for you. Carbon dioxide binds to RuBP.

(iii)[4]

Outline the reactions in the stroma that result in the formation of a polysaccharide, such as alginate. The first sentence has already been supplied for you. Carbon dioxide binds to RuBP.

(b(i))[2]

With reference to Table 5.1, explain the difference in the rate of photosynthesis at high carbon dioxide concentration compared with low carbon dioxide concentration.

(b(ii))[3]

With reference to Table 5.1, describe and explain how increasing day length affects the rate of photosynthesis for the Z. marina in high carbon dioxide concentration.

(c(i))[2]

With reference to Fig. 5.2, explain the effect on the rate of photosynthesis as pH rises from 8.1 to 8.4.

(c(ii))[1]

The lower pH values in Fig. 5.2 represent ocean acidification. Suggest why the results at the lower pH values do not fully back up the idea that seaweeds can help reduce ocean acidification.

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