Before You Begin

Question #46755

Difficulty: 8/10 | 🟢 Free

The Question

Both the counter-current mechanism in the human kidney and chemiosmotic ATP synthesis in chloroplasts rely on the continuous expenditure of energy to maintain steep electrochemical or osmotic gradients. If a pharmacological agent selectively inhibits the active transport of $NaCl$ in the ascending limb of the Loop of Henle, and a mutation inactivates the Oxygen Evolving Complex (OEC) in the thylakoid lumen, what will be the primary physiological fallout in each system respectively?

Options

A.
Obligatory water reabsorption in the PCT ceases; cyclic photophosphorylation becomes the sole source of $NADPH$ .
B.
The corticomedullary osmotic gradient collapses, rendering ADH ineffective; the proton motive force dissipates, halting ATP synthesis via the $CF_0-CF_1$ complex.
C.
The vasa recta actively secretes $NaCl$ to compensate; the stroma becomes highly acidic due to proton leakage.
D.
Dilute urine is produced due to increased urea recycling; the cytochrome $b_6f$ complex reverses its pumping direction to maintain the gradient.

Check Your Answer

Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Regulatory_Failure

Understand how NOT, EXCEPT, and logical constraints are used to manipulate exam results.

Concepts Behind This Question

Thylakoid Lumen Sequestration|Counter-Current Exchanger|ADH(Vasopressin)

Why This Question Is Tricky

Common Mistakes

Conceptual Pivot: Students often memorize the final effectors ('ADH absorbs water' or 'ATP synthase makes ATP') without realizing these structures are thermodynamically useless without their underlying gradients.

The trap lies in assuming ADH can still concentrate urine if the collecting duct is permeable, ignoring that osmosis strictly requires the medullary interstitial gradient established by the Loop of Henle.

Quick Facts About This Question

Question Information

Subject	Biology
Chapter	Cell – The Unit of Life - Class 11
Concept	Thylakoid Lumen Sequestration
Difficulty	8
Cognitive Load	5
Target Solve Time	120 sec
Access	Free