The Question is from neet-botany , and it was created by the author Mr. NARESH KUMAR K

Question

Certain integral membrane proteins facilitate the diffusion of molecules across the membrane without directly binding to the transported molecule.  These proteins create a continuous aqueous pathway through the lipid bilayer. Which of the following is the BEST example of such facilitated diffusion?

Mr. NARESH KUMAR K · Accepted Answer

## CORE INFORMATION
✓ **Answer**: C
## CONCEPT FRAMEWORK
 **Primary Concept**: Facilitated Diffusion
 **Related Topics**: Membrane transport, integral membrane proteins, aquaporins, ion channels
 **Prerequisites**: Understanding of cell membranes, passive transport mechanisms.
## SOLUTION PATHWAY
**Given Information**:
The question describes a type of facilitated diffusion where a protein creates a continuous aqueous pathway across the membrane, without directly binding to the transported molecule.
**Method & Steps**:
1. **Identify the key characteristic**: The key is the creation of a continuous aqueous pore through the membrane.
2. **Analyze the options**: 
    a) GLUT transporters bind to glucose molecules before transporting them across the membrane.
    b) The sodium-potassium pump is an active transport mechanism, requiring energy (ATP) to move ions against their concentration gradients.
    c) Aquaporins are channel proteins that form pores allowing water molecules to pass through the membrane without direct binding. This perfectly matches the description.
    d) Chloride channels are gated, meaning their opening and closing is regulated, and they typically involve some level of interaction with the transported ion.
3. **Select the best example**: Aquaporins are the best example of facilitated diffusion that forms a continuous aqueous pathway without direct binding to the transported molecule.

## OPTION ANALYSIS
A :x: GLUT transporters use facilitated diffusion, but they bind to glucose molecules during transport.
B :x: The sodium-potassium pump is active transport, not passive facilitated diffusion.
C ✓: Aquaporins create water channels, forming a continuous aqueous pathway through the membrane. Water molecules pass through without direct binding to the aquaporin protein.
D :x: Chloride channels are gated ion channels; their mechanism is more complex than simply creating a continuous aqueous pathway.
## LEARNING AIDS
 **Common Mistakes**:
  1. Confusing facilitated diffusion with active transport:  Remember that facilitated diffusion is still passive transport; it doesn't require energy. 
  2. Focusing on the 'facilitated' aspect and overlooking the 'continuous aqueous pathway' requirement:  Pay attention to all parts of the question's description.
 **Quick Tips**:
  1.  Visualize the different transport mechanisms.  Draw diagrams to help understand how each works.
  2. Memorize the key characteristics of different membrane proteins (e.g., aquaporins are water channels, GLUT transporters are carrier proteins).

Mr. NARESH KUMAR K · Answer

GLUT transporters moving glucose

Mr. NARESH KUMAR K · Answer

Sodium-potassium pump maintaining ion gradients

Mr. NARESH KUMAR K · Answer

The correct Option is "Aquaporins transporting water"

Mr. NARESH KUMAR K · Answer

Chloride channels gated by voltage

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