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Chapter 38: Problem 35

How would muscle contractions be affected if ATP was completely depleted in a muscle fiber?

Short Answer

Expert verified
Without ATP, muscles would enter a state of rigor and remain contracted, unable to relax.

Step by step solution

01

Understanding Muscle Contraction

Muscle contraction is driven by the interaction between the proteins actin and myosin within the muscle fibers. Specifically, myosin heads attach to binding sites on actin filaments to form cross-bridges and pull the actin filaments inward, resulting in contraction.
02

Role of ATP in Muscle Contraction

ATP (adenosine triphosphate) is critical for muscle contraction. It provides the energy that myosin heads need to detach from the actin filament after a power stroke. Then, ATP is hydrolyzed to ADP and inorganic phosphate, which re-cocks the myosin head into a position for another cycle.
03

What Happens Without ATP

If ATP is completely depleted, myosin heads cannot detach from actin after a power stroke. This results in a condition known as rigor, where muscles become stiff and cannot relax.
04

Conclusion

Without ATP, muscles would remain in a contracted state because the myosin heads would be unable to release from the actin filaments, preventing any further contraction or relaxation.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

ATP role in muscle contraction
ATP, or adenosine triphosphate, is essential for muscle contraction. It provides the energy necessary for several key steps in the contraction cycle. During a muscle contraction, ATP binds to the myosin head after it has completed a power stroke. This binding allows the myosin head to detach from the actin filament, enabling the muscle to relax momentarily. The hydrolysis of ATP into ADP (adenosine diphosphate) and inorganic phosphate then 're-cocks' the myosin head, positioning it for the next cycle of contraction. Without ATP, the myosin heads would remain attached to the actin, leading to muscle stiffness and preventing further contractions.
actin and myosin interaction
Muscle contraction relies on the interaction between two key proteins: actin and myosin. Actin filaments serve as the tracks along which myosin heads move. The myosin heads attach to specific binding sites on the actin filaments to form cross-bridges. Once attached, the myosin heads pull the actin filaments inward in a process known as the power stroke. This action shortens the muscle fiber, causing contraction. After the power stroke, ATP is needed for the myosin heads to release from the actin filaments and reset for another cycle. This highly coordinated process repeats many times during muscle contraction, enabling movements ranging from simple twitches to complex motions.
muscle rigor
Muscle rigor, also known as rigor mortis when it occurs after death, is a condition where muscles become stiff and unable to relax. This happens when ATP levels are depleted. Without ATP, the myosin heads cannot detach from the actin filaments after a power stroke. As a result, the muscles remain in a contracted state. In living organisms, this rigidity can be temporary and is usually resolved once ATP is replenished. However, in a dead organism, the lack of ATP continues, leading to permanent muscle stiffness until the muscle tissues begin to break down naturally.

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Most popular questions from this chapter

The epiphyseal plate: a. is arranged as rods or plates b. contains the bone's blood vessels and nerve fibers c. is responsible for the lengthwise growth of Iong bones d. synthesizes and secretes bone matrix

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The ability of a muscle to generate tension immediately after stimulation is dependent on: a. myosin interaction with the \(\mathrm{M}\) line b. overlap of myosin and actin c. actin attachments to the \(\mathrm{Z}\) line d. none of the above
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