Question

Given below are two statements:
Statement I: Phosphocreatine is formed from ATP in the resting cell and ATP is low. Phosphocreatine thereby acts as a buffer in the cell that contains creatine kinase.
Statement II: ATP is formed in the cell in mitochondria and chloroplast by a mechanism i.e., essentially ATP driven ion transport operating in reverse.
In the light of the above statements, choose the most appropriate answer from the options given below

• A. Both Statement I and Statement II are true
• B. Both Statement I and Statement II are false
• C. Statement I is correct but Statement II is false
• D. Statement I is incorrect but Statement II is true

Hint:

Bioenergetics: Phosphocreatine is charged when ATP is HIGH (resting). ATP Synthase is a chemiosmotic proton pump operating in reverse driven by $\Delta p$.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Phosphocreatine acts as a temporal high-energy phosphagen buffer synthesized when ATP is high, while ATP synthase operates as a reverse rotary proton pump.
Key Formula or Approach:
\[ \text{Creatine} + \text{ATP} \xrightleftharpoons[\text{Active contraction: ATP regeneration}]{\text{Resting cell: ATP high}} \text{Phosphocreatine} + \text{ADP} \]

Step 2: Detailed Explanation:
1. Statement I: In resting muscle cells, phosphocreatine is synthesized by creatine kinase when cellular ATP levels are HIGH (storing excess high-energy phosphate). During active contraction when ATP levels fall, the reaction reverses to replenish ATP. Because Statement I claims phosphocreatine is formed when 'ATP is low', Statement I is incorrect.
2. Statement II: Peter Mitchell's chemiosmotic hypothesis demonstrates that $\text{F}_1\text{F}_o$-ATP synthase in mitochondria and chloroplasts is fundamentally a rotary proton-translocating ATPase operating in reverse, utilizing the electrochemical proton-motive force ($\Delta p$) to synthesize ATP. Hence, Statement II is true.

Step 3: Final Answer:
Thus, Statement I is incorrect but Statement II is true, matching option (D).