Question

B) Which of the following mechanisms allow ATP synthase complex to release ATP as proton flow occurs?

1. activation

2. conformational coupling

3. chemiosmosis

4. oxidative phosphorylation

Answer 1

ATP synthase complex - it is a mitochondrial complex ( enzyme) embeded in the inner membrane of mitochondria .it catalizes the synthesis of ATP from ADP , using a proton flux ( proton flow) according to a proton gradiant or electrochemical gradiant . .  

ATP synthase complex produce ATP through chemiosmosis process ( option 3 is right option )

chemiosmosis - it is the movement of ions accross the membrane . in case of ATP syunthase situated at inner membrane of mitochondria , hydrogen ions or proton ( pumped by electron transport chain ) diffuse ( through ATP synthase)  from high proton concentration area to a lower proton concentration area as similar as osmosis . the difference of concentration of protons accross the two side of the membrane ( or ATP synthase) will create a electrochemical concentration gradient . for this a proton motive force will be generated and proton flux will occur from higher concentraion to lower concentration of protons . by using this proton flux ATP synthase enzyme catalizes the releasing of  ATP from ADP . so chemiosmosis is the mechanism by which ATP synthase release ATP . therefore option 3 is the right answer .

oxidative phosphorylation - it is a metabolic pathway in which ATP is also produced by using chemical energy of oxygen molecule (hence named oxidative and  ADP is phosphorylated and become ATP hence named phosphorylation ). it is also occurs in mitochondria . in this mechanism electrons are transfered from electron donor ( NADH₂ or FADH₂ ) to electron acceptor ( oxygen ) and this redox reaction release the energy . but ATP synthase does not use this mechanism to produce ATP . hence option 4 can't be the right option .

conformational coupling - it is the conformational change of energy linked protein by which energy transduction occurs .this mechanism is linked with Ca²⁺ entry , oxidative phosphorylation and this mechanism is also used in mitochondria and chloroplast to produce energy or ATP but ATP synthase does not use this mechanism so this ( optrion 2 ) is wrong option .

activation is a general mechanism . ATP synthase is also activated by proton gradient for releasing  ATP . but with out proton motive force / chemoosmosis ATP synthase can not produce ATP by only become activated . so only activation is not the cause of ATP releasing . hence 1st option is also not applicable .