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

Question

A prokaryotic cell lacking MreB protein is most likely to exhibit which shape?

Mr. NARESH KUMAR K · Accepted Answer

## CORE INFORMATION
✓ **Answer**: C
## CONCEPT FRAMEWORK
 **Primary Concept**: Role of MreB protein in prokaryotic cell shape
 **Related Topics**: Prokaryotic cell structure, cytoskeleton, cell morphology
 **Prerequisites**: Basic understanding of prokaryotic cells and their components.
## SOLUTION PATHWAY
**Given Information**:
A prokaryotic cell lacks MreB protein.
**Method & Steps**:
1. Identify the function of MreB protein.
  Reasoning: MreB is a prokaryotic homolog of actin. It plays a crucial role in determining cell shape by forming filaments that dictate cell wall synthesis.  In rod-shaped bacteria, MreB forms helical filaments beneath the cytoplasmic membrane, guiding the synthesis of peptidoglycan to create the rod shape.
  Formula/Rule: No formula is directly applicable.
2. Predict the consequence of MreB absence.
  Working: If MreB is absent, the organized synthesis of peptidoglycan is disrupted, leading to a loss of rod shape. The cell would likely adopt a simpler, less organized shape.
  Key Point: The absence of MreB does not necessarily lead to cell lysis, but rather a change in morphology.
3. Determine the most likely shape.
  Result: Spherical (coccus) shape is the most likely outcome because it represents the simplest and most energetically favorable shape in the absence of a guiding structure like MreB.
  Verification: This is consistent with experimental observations where MreB mutants often exhibit a spherical morphology.
 ## OPTION ANALYSIS
A :x: Rod-shaped bacteria require MreB for their shape.
B :x: Spiral shapes also require specific cytoskeletal elements for their structure, which MreB is not solely responsible for.
C ✓: Spherical shape is the default shape in the absence of a cytoskeletal framework like that provided by MreB.
D :x: Filamentous shapes require specific mechanisms for elongation and maintenance, which are not present when MreB is absent.
 ## LEARNING AIDS
 **Common Mistakes**:
  1.Assuming MreB is the only factor determining cell shape: Other factors, though less prominent, can influence cell shape.
  2.Confusing MreB with other cytoskeletal proteins: MreB has a specific role distinct from other prokaryotic cytoskeletal elements.
 **Quick Tips**:
  1.Remember the analogy of MreB to actin in eukaryotic cells.  Actin is crucial for maintaining cell shape in eukaryotes.
  2.Think of the simplest possible shape for a cell without a defined cytoskeleton – a sphere.

Mr. NARESH KUMAR K · Answer

Rod-shaped

Mr. NARESH KUMAR K · Answer

Spiral

Mr. NARESH KUMAR K · Answer

The correct Option is "Spherical"

Mr. NARESH KUMAR K · Answer

Filamentous

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