Multiple Choice
The box in the image below surrounds what structure?
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9. Muscle Tissue
Sliding Filament Theory and the Sarcomere
3:13 minutesProblem 17
Textbook Question
What is the calcium-binding protein in smooth muscle tissue?
Verified step by step guidance1
Understand that calcium-binding proteins are molecules that bind calcium ions (Ca^{2+}) and play a crucial role in muscle contraction by regulating calcium availability.
Recall that in skeletal muscle, the primary calcium-binding protein is troponin, but smooth muscle lacks troponin.
Identify that in smooth muscle tissue, the calcium-binding protein responsible for initiating contraction is calmodulin.
Recognize that calmodulin binds calcium ions, which then activates myosin light-chain kinase (MLCK), leading to smooth muscle contraction.
Conclude that the calcium-binding protein in smooth muscle tissue is calmodulin.
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Video duration:
3mKey Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Calcium-Binding Proteins
Calcium-binding proteins are molecules that can bind calcium ions, playing a crucial role in cellular signaling and muscle contraction. They regulate calcium availability and mediate processes triggered by calcium influx, essential for muscle function.
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Smooth Muscle Tissue
Smooth muscle tissue is an involuntary, non-striated muscle found in walls of internal organs like blood vessels and the digestive tract. Its contraction is regulated differently from skeletal muscle, relying heavily on calcium-binding proteins for activation.
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Calmodulin in Smooth Muscle
Calmodulin is the primary calcium-binding protein in smooth muscle. When calcium binds to calmodulin, it activates myosin light-chain kinase, initiating contraction. This mechanism is distinct from skeletal muscle, which uses troponin for calcium regulation.
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