Question

Would you expect rotenone to be more, less or equally poisonous as carbon monoxide? Explain your answer

Which metabolic poison described in question 3 will affect oxygen production in chloroplasts? Why other poisons described in question 3 do not affect oxygen production in chloroplasts? Explain your answer

1. In the lab, metabolic poisons can be used to study ATP synthesis and oxygen consumption. The action of several metabolic poisons is given in the table below:

Poison	Action
Oligomycin	Binds and blocks the proton channel in ATP synthase
Carbon monoxide	Inhibits cytochrome oxidase
2,4-dinitrophenol (DNP)	Binds protons and moves them down their electrochemical gradient
Rotenone	Blocks electron transfer at NADH dehydrogenase

Answer 1

Answer:

a) Rotenone inhibits electron transport chain and protein pump at complex I.

Carbon Monoxide inhibit complex III.

So when rotenone inhibit complex I, chain will proceed by Complex II.

But when complex III is inhibited by carbon monoxide, chain is blocked completely.

So carbon monoxide is more poisonous.

b) 2 4 dinitrophenol dessipate proton gradient across mitochondria and chloroplast membrane.

Oligomycin act in complex V of electron transport chain.

Carbon monoxide act at complex III of electron transport chain.

Rotenone act at complex I of electron transport chain.

Where as 2 4 DNP uncouples oxidative phosphorylation, cause release of calcium from mitochondrial stores and prevent calcium reuptake. DNP act as protonophore allowing protons to leak across membrane.