What are the effects of addition of these chemicals to actively respiring cells ? Which of them would lead to INHIBITION of aerobic respiration ? Would cytochromes be actually taken up by cells ?

a.addition of CO

b.addition of CO2

c.addition of cytochromes and flavoprotein

  • 6
    $\begingroup$ Come on. I know that you know the answers to almost all of them :) $\endgroup$
    Oct 16, 2013 at 9:13
  • $\begingroup$ I hope I'm not wrong here: More CO in the cells cause numbness over that region by temporarily inhibiting the functions performed by the cell. (I guess my Biology teacher once told us how some body parts go numb after sitting for hours. Wherein the respiration process is slow with less intake of O2 which causes accumulation of CO in the cells of the parts which is cut out of blood supply). $\endgroup$
    – Pradeep S
    Oct 16, 2013 at 10:00
  • $\begingroup$ @WYSIWYG I actually wanted answers to mainly these 3 and I have edited the question. The question given in my homework is a bit twisted(not exactly the question I am asking) so I think I just got crazy and asked some silly things :) $\endgroup$
    – biogirl
    Oct 16, 2013 at 18:30
  • 1
    $\begingroup$ If you're loving Biology, then you can either try using some sort of Library or Wikipedia, and I am really amazed with that lot much of Questions :) I don't even have answers that much! :P Good girl.. $\endgroup$ Oct 16, 2013 at 20:00

1 Answer 1


Carbon Monoxide "CO" would definitely inhibit aerobic respiration. This is in fact the mechanism of the toxicity of compounds such as carbon monoxide and cyanide, namely, carbon monoxide binds (coordinates) with an affinity several orders of magnitude greater than oxygen to the heme group of mitochrondrial cytochrome oxidase, thus inhibiting the enzyme. When the respiratory electron chain is no longer drawn by the reduction of molecular oxygen, the hydrogen ion gradient across the mitochrondrial inner membrane is depleted, and ATP production halts.

Carbon dioxide would not effect the electron transport chain directly, but is rather involved in the reactions of the citric acid cycle, although, in all likelihood, the cell would die of acidosis before CO₂ concentrations became great enough to reverse the citric acid cycle. Cytochromes and flavoproteins are complex molecules that if the cell were to endocytize them, it would simply digest them.

I do not know your degree of experience in biochemistry, but if you wish, search on the internet for protein structural images of cytochrome oxidase or hemoglobin bound to oxygen and carbon monoxide. Oxygen binds the iron of the heme group at an angle, while carbon monoxide binds directly perpendicular to the heme ring. This difference in geometry is partially responsible for the differential affinity of the two species for heme.


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