In both mitochondria and chloroplasts, atp synthesis is coupled to electron transport. which one of the following is likely to affect the coupling of electron transport to atp synthesis in both of these systems?

a) the absence of light
b) the removal of oxygen
c) leucinostatin, an atp synthase inhibitor
d) a photosystem ii inhibitor

B- Removal of oxygen.

Explanation:

This is because oxygen is the final acceptor of electrons in the process of ATPs synthesis called CHEMIOSMOSIS in both mitochondrial and chloroplast. In its absence Electron transport chain will take not place because NAD+ will not be regenerated to supply energy for ETC and therefore no ATP synthesis.

As electron   moves from a protein carrier at a higher energy level to another one at lower energy level   in the thylakoids membranes of chloroplasts and inner mitochondrial membranes of mitochondrial; ENERGY is released. Part of this energy is used to pump H+ /protons from the inner membrane of mitochondrial and thylakoid membranes of chloroplast into the outer Cytosols.  The proton were produced from   the splitting of hydrogen atoms attached to the coenzymes NADH+ (oxidation of NADH+ to NAD+)  and FADH

Continuous pumping of these ions from constant supply of energy by electron movement uphill and downhill, created higher concentration gradients of hydrogen ions in the Cytosols compared to inner stroma of chloroplasts and matrix of mitochondria

These higher concentration gradients drive down protons along the protein channels for hydrogen ions to reach ATPase synthase. ( protein that transfer energy from hydrogen ions for ATPs synthesis) it is located in the hydrogen ions channels.

It catalysis the reaction or phosphorylation of inorganic phosphate with Adenosine diphosphates to form adenosine triphosphate.  

               (Adenosine diphosphates)ADP + ( Pi )   inorganic phosphate      >  ATP (adenosine  triphosphate.)  .

Oxygen on reaching the final protein carrier, it picks up proton, and electron to form water ,end of cellular respiration.

In the absence of oxygen, electron transport chain cannot take place because no oxygen to accept the final electron, therefore no electron will be available for Electron transport chain to transport for ENERGY needed for pumping protons, As a result no ATP will be generated as shown above, since   regeneration of NAD+ will be stopped.

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