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A poison blocks cytochrome c oxidase (complex IV) in the mitochondria of a cell…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A poison blocks cytochrome c oxidase (complex IV) in the mitochondria of a cell.
- What happens to the carriers of the chain before complex IV?
- What happens to the NADH?
- What happens to the Krebs cycle?
- How many ATP does the electron transport system make now?
Need a reminder? The key ideaShow
The electron transport system lies on the inner membrane. Electrons go from NADH to complex I, and from FADH to complex II, then through ubiquinone, complex III, cytochrome c and complex IV to oxygen, which becomes water. One NADH gives 3 ATP and one FADH gives 2 ATP. Each carrier makes one water.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) They cannot pass their electrons on. They stay full of electrons, in their reduced form.
Step 2. (b) The NADH is not oxidised, so no NAD is made.
Step 3. (c) The Krebs cycle runs out of NAD and FAD, and it stops.
Step 4. (d) No protons are pumped, so ATP synthase makes no ATP: .
Answer: (a) they stay reduced; (b) not oxidised; (c) it stops; (d) ATP.
Watch out. Glycolysis can go on for a short time, because the cell can turn to fermentation, but the ATP is very small.
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