The Question is from neet-zoology excretory-products-and-their-elimination , and it was created by the author A SUBRAMANYAM

Question

What is the obligatory water reabsorption?

A SUBRAMANYAM · Accepted Answer

## CORE INFORMATION
✓ **Answer**: C
## CONCEPT FRAMEWORK
	**Primary Concept**: Obligatory water reabsorption in the nephron.
	**Related Topics**: Renal physiology, Nephron structure, Water permeability in different parts of the nephron.
	**Prerequisites**: Basic understanding of kidney function and nephron anatomy.
## SOLUTION PATHWAY
**Given Information**:
	The question asks about the location(s) where obligatory water reabsorption occurs.
	Obligatory water reabsorption is the passive movement of water down its concentration gradient.
**Method & Steps**:
	1. Identify the parts of the nephron involved in water reabsorption: The Proximal Convoluted Tubule (PCT) and the Loop of Henle are the primary sites.
		Reasoning: The PCT is highly permeable to water due to the presence of aquaporins, and the descending limb of the loop of Henle is also permeable to water.
		Formula/Rule:  Obligatory water reabsorption is driven by osmotic gradients.
	2. Determine if water reabsorption in PCT and Loop of Henle is considered obligatory: Both PCT and descending limb of loop of Henle are sites of obligatory water reabsorption.
		Working: Water moves passively following the osmotic gradient created by the reabsorption of solutes.
		Key Point: Obligatory reabsorption is not regulated by hormones, unlike facultative reabsorption in the collecting duct.
	3. Identify the correct option: Both PCT and loop of Henle are sites of obligatory water reabsorption.
		Result: Option C is the correct answer.
		Verification: The other options are incorrect because they either only specify one location or describe secretion, not reabsorption.
 ## OPTION ANALYSIS
[A] :x: This option is partially correct, but it doesn't include the loop of Henle.
[B] :x: This option is partially correct, but it doesn't include the PCT.
[C] ✓: Both the PCT and the loop of Henle are sites of obligatory water reabsorption.
[D] :x: This option describes water secretion, not reabsorption.
 ## LEARNING AIDS
	**Common Mistakes**:
		1.[Error 1]: Confusing obligatory and facultative reabsorption. [How to avoid]: Remember that obligatory reabsorption is passive and occurs in PCT and loop of Henle, while facultative is hormonally regulated and occurs in the collecting duct.
		2.[Error 2]: Thinking water is actively transported during reabsorption. [How to avoid]: Water reabsorption is mostly passive and driven by osmotic gradients.
	**Quick Tips**:
		1.[Helpful shortcut]: Remember the PCT and descending limb of loop of Henle are always permeable to water and reabsorb water obligatorily.
		2.[Memory aid]: Think of 'obligatory' as 'unavoidable' or 'passive' water reabsorption.

A SUBRAMANYAM · Answer

Reabsorption of water from PCT

A SUBRAMANYAM · Answer

Reabsorption of water from loop of Henle

A SUBRAMANYAM · Answer

The correct Option is "Both (a) and (b)"

A SUBRAMANYAM · Answer

Water secretion by Bowman’s capsule

NEET Zoology Excretory Products And Their Elimination MCQs

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