Question

which of the following sequences correctly represents the flow of electrons during photosynthesis?
nadph→o2→co2
h2o→nadph→calvin cycle
h2o→photosystem i→photosystem ii
nadph→electron transport chain→o2

Explanation:

• In photosynthesis, water (\(H_2O\)) is split in the light - dependent reactions. The electrons from \(H_2O\) are used to generate \(NADPH\).
• The \(NADPH\) then donates its electrons to the Calvin cycle (light - independent reactions) for the reduction of \(CO_2\) to form organic compounds.
• For the option \(NADPH

ightarrow O_2
ightarrow CO_2\): \(NADPH\) is an electron donor, not an electron acceptor from \(O_2\), and \(O_2\) is a by - product of the splitting of water, not a direct participant in this electron flow sequence as described in this option.

• For the option \(H_2O

ightarrow\) photosystem \(I
ightarrow\) photosystem \(II\): In the light - dependent reactions, electrons flow from \(H_2O\) to photosystem \(II\) first, then to the electron transport chain, and then to photosystem \(I\).

• For the option \(NADPH

ightarrow\) electron transport chain \(
ightarrow O_2\): \(NADPH\) is formed at the end of the non - cyclic electron flow (after the electron transport from photosystem \(I\)), and \(O_2\) is produced from the splitting of water, not from an electron flow that starts with \(NADPH\) as described here.

Answer:

\(H2O
ightarrow NADPH
ightarrow Calvin\ cycle\)