[Princess_perfect786]

can anyone help me out with the following question?

Herbicides (weedkillers) interfere with electron transport by accepting electrons. Suggest how this causes plants to die (3 marks)

so far i've written:

NADPH in the plant can no longer accept the electrons. this means that NADPH no longer provides energized electrons to the calvin cycle

I'm not sure if what i've written is correct, though

[Blackspur]

this should explain everything

http://www.youtube.com/watch?v=mQMVHhxTtLc

[Organ]

(Original post by Princess_perfect786)
can anyone help me out with the following question?

Herbicides (weedkillers) interfere with electron transport by accepting electrons. Suggest how this causes plants to die (3 marks)

so far i've written:

NADPH in the plant can no longer accept the electrons. this means that NADPH no longer provides energized electrons to the calvin cycle

I'm not sure if what i've written is correct, though

NADPH will never accept electrons, it is NADP that accepts electrons after they have passed down the electron transport chain in the light dependant reactions. I assume herbicides prevent NADH from from being reduced to NADPH.

So...

1. NADP is unable to accept electrons and be reduced to NADPH

2. NADPH is not available in the Calvin Cycle (where it is required to convert GP to TP)

3. Also, electrons are unable to pass down the electron transport chain - as a result no energy is generated. Without energy, no hydrogen protons can be pumped into the thylakoid lumen

4. Because no hydrogen ions can be pumped into the thylakoid lumen - no concentration gradient can be established - hence no hydorgen ions pass down the concentration gradient via the ATP synthase protein embedded in the thylakoid membrane - thus no ADP can be phosphorylated - and thus no ATP is synthsised

So; no NADPH or ATP is available in the Calvin Cycle - thus GP can not be converted to TP. With no TP glucose cannot be synthesised (2 x TP = 1 gluocose). No glucose = no energy = plant death.