Chapter 7, Problem 1TYU

The immediate energy source that drives ATP synthesis by ATP synthesis during oxidative phosphorylation is the

1. A.    oxidation of glucose and other organic compounds.
2. B.     flow of electrons down the electron transport chain.
3. C.     H⁺ concentration gradient across the membrane holding ATP synthase.
4. D.    transfer of phosphate to ADP.

Summary Introduction

Introduction:

ATP is the energy currency of our body. It is synthesized in the mitochondria by oxidation of glucose (mostly). The process is called oxidative phosphorylation.

Answer to Problem 1TYU

Correct answer:

TCA cycle helps in the production of an electron motive force that is passed along the complexes in the inner mitochondrial membrane (electron transfer chain) and converted to proton motive force. This positive force is then responsible for ATP synthesis. Therefore, option (C) is correct.

Explanation of Solution

Reason for the correct statement:

When the concentration of protons is high outside the membrane of mitochondria, protons are forced through the enzyme ATP synthase. This proton movement makes the ATP synthase to rotate and the production of APT from ADP and inorganic phosphate (Pi).

Option (C) is given as “${\text{H}}^{\text{+}}$ concentration gradient across the membrane holding ATP synthase”.

“The immediate energy source that drives ATP synthesis by ATP synthase during oxidative phosphorylation is the ${\text{H}}^{\text{+}}$ concentration gradient across the membrane holding ATP synthase”. Thus, it is the right answer.

Hence, the option (c) is correct.

Reasons for the incorrect statements:

Option (A) is given as “oxidation of glucose and other organic compounds”.

Oxidation of glucose and other organic material actually occurs where the process of ATP synthesis starts; however, it is not the immediate energy source for ATP synthesis. Thus, it is the wrong answer.

Option (B) is given as “flow of electrons down the electron transport chain”.

ETC is responsible for creating the gradient, but it is not the immediate energy source for ATP synthesis. Thus, it is the wrong answer.

Option (D) is given as “transfer of phosphate to ADP”.

The immediate energy source that drives ATP synthesis by ATP synthase during oxidative phosphorylation is the ${\text{H}}^{\text{+}}$ concentration gradient across the membrane holding ATP synthase but not the transfer of phosphate to ADP. Thus, it is the wrong answer.

Hence, options (A), (B), and (D) are incorrect.

Conclusion

Proton gradient created in the inter-membrane space is the reason for ATP generation by enzyme ATP synthase.