The Question is from neet-zoology locomotion-and-movement structure-of-contractile-proteins, and it was created by the author Mr. BALACHANDRA.N

Question

During muscle contraction, the conformational change in the myosin head that leads to the power stroke is primarily driven by:

Mr. BALACHANDRA.N · Accepted Answer

## CORE INFORMATION
✓ **Answer**: C
## CONCEPT FRAMEWORK
 **Primary Concept**: Muscle contraction mechanism
 **Related Topics**: Myosin, actin, ATP hydrolysis, cross-bridge cycle
 **Prerequisites**: Basic understanding of protein structure and function, energy metabolism
## SOLUTION PATHWAY
**Given Information**:
  The question asks about the primary driver of the myosin head power stroke during muscle contraction.
**Method & Steps**:
 1. Understanding the Cross-Bridge Cycle: Muscle contraction involves a cyclical interaction between myosin and actin filaments.  This cycle includes attachment, power stroke, detachment, and cocking.
  Reasoning: The power stroke is the conformational change in the myosin head that pulls the actin filament towards the center of the sarcomere.
  Formula/Rule: No specific formula is directly applicable here, but understanding the sequence of events in the cross-bridge cycle is crucial.
 2. Analyzing the Role of ATP Hydrolysis and Phosphate Release: ATP hydrolysis provides the energy for the myosin head to bind to actin.  The release of inorganic phosphate ($P_i$) is the trigger for the power stroke.
  Working:  ATP binds to the myosin head, causing a conformational change.  This is followed by ATP hydrolysis to ADP and $P_i$. The release of $P_i$ is the critical event that induces the conformational change in the myosin head, leading to the power stroke.
  Key Point: While ATP hydrolysis provides the energy, the release of $P_i$ is the direct trigger for the power stroke.  The subsequent release of ADP allows for detachment and the cycle to repeat.
 3. Eliminating Incorrect Options:  Binding of ATP initiates the cycle but doesn't directly cause the power stroke.  Calcium ion binding to troponin is essential for initiating contraction by exposing the myosin-binding sites on actin, but it's not the direct trigger for the power stroke itself.
  Result: The release of inorganic phosphate ($P_i$) is the primary driver of the conformational change in the myosin head that leads to the power stroke.
  Verification: This aligns with the established understanding of the cross-bridge cycle in muscle contraction.
 ## OPTION ANALYSIS
A :x: Hydrolysis of ATP provides the energy, but the power stroke is triggered by $P_i$ release.
B :x: ATP binding initiates the cycle, but doesn't directly cause the power stroke.
C ✓: Release of inorganic phosphate ($P_i$) directly triggers the power stroke.
D :x: Calcium ion binding to troponin is crucial for initiating contraction but doesn't directly cause the myosin head conformational change.
 ## LEARNING AIDS
 **Common Mistakes**:
  1.Confusing ATP hydrolysis with the power stroke trigger:  While ATP hydrolysis is necessary, the release of $P_i$ is the direct trigger.
  2.Overlooking the sequential steps in the cross-bridge cycle: Understanding the order of events is key to understanding the power stroke mechanism.
 **Quick Tips**:
  1.Remember the sequence: ATP binding, hydrolysis, $P_i$ release (power stroke), ADP release.
  2.Visualize the cross-bridge cycle using diagrams to understand the conformational changes.

Mr. BALACHANDRA.N · Answer

Hydrolysis of ATP

Mr. BALACHANDRA.N · Answer

Binding of ATP

Mr. BALACHANDRA.N · Answer

The correct Option is "Release of inorganic phosphate (Pi)"

Mr. BALACHANDRA.N · Answer

Binding of Calcium ions to troponin

NEET Zoology Locomotion And Movement Structure Of Contractile Proteins MCQs

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