Question

you need to find out why the gbr water is inhibiting (stopping) photosynthesis in the algae. the three major parts of photosynthesis are psi, psii and the calvin cycle. the database has provided 3 things that could be inhibiting photosynthesis: high sea temperatures, paraquat, and diuron.

normal sea water

gbr sea water

calvin cycle

high sea temperature | photosystem i
paraquat | photosystem ii
diuron |

atp	5.2 mm	0.1 mm ⬇️
nadph	5.3 mm	0.1 mm ⬇️
sugar	6.0 mm	0.2 mm ⬇️

justify your choice by writing a hypothesis to explain how it has stopped the algae from making atp, nadph and sugars. you will be able to revise your hypothesis as you do more experiments.

Explanation:

Paraquat targets Photosystem I (PSI), which is critical for the final steps of the light-dependent reactions that produce NADPH and ATP. When PSI is inhibited, the electron transport chain cannot fully function, drastically reducing the production of ATP and NADPH. Since the Calvin cycle relies on ATP and NADPH to fix carbon and produce sugar, low levels of these molecules directly lead to a sharp drop in sugar synthesis. The observed low levels of ATP, NADPH, and sugar in GBR water match the expected effects of paraquat inhibition.

Answer:

Hypothesis: The GBR water contains paraquat, which inhibits Photosystem I (PSI) in the algae's light-dependent reactions. This inhibition disrupts the electron transport chain, preventing the production of ATP and NADPH. With insufficient ATP and NADPH, the Calvin cycle cannot run effectively, leading to drastically reduced sugar synthesis, which matches the low measured levels of ATP, NADPH, and sugar in GBR sea water.