Why do the electrons that enter at complex II ultimately yield fewer adenosine triphosphate molecules?
AThey are handed straight to oxygen molecules
BThey skip the proton pump of the first complex
CThey are carried out into the cytoplasm first
DThey lose energy to heat inside the matrix
Answer & Solution
Correct answer: B. They skip the proton pump of the first complex
1. Complex II receives its electrons directly, without them passing through complex I.
2. Those electrons therefore bypass and do not energize the proton pump in the first complex.
3. Fewer protons are pumped as a result.
4. The number of adenosine triphosphate molecules ultimately obtained is directly proportional to the number of protons pumped across the inner mitochondrial membrane.
5. Fewer protons pumped therefore means fewer adenosine triphosphate molecules made.
6. The electrons still travel the rest of the chain to oxygen, so an answer sending them straight to oxygen skips three complexes.
_Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 7 "Cellular Respiration", section 7.4 Oxidative Phosphorylation_
Related questions
In type 2 diabetes the oxidation efficiency of NADH is reduced, which affects:Where does the carbon dioxide released during cellular respiration come from?The citric acid cycle is described as amphibolic because its intermediates can also be useHydrogen ions pumped by the electron transport chain accumulate in the:The mobile carrier connecting the first and second complexes to the third is:How many complexes make up the electron transport chain?Making ATP by chemiosmosis is called oxidative phosphorylation because the process involveChemiosmosis accounts for roughly what share of the ATP made during glucose catabolism?