20 Questions
What protein is a calcium-sensitive switch that regulates myosin’s access to the actin microfilament?
Troponin
What defines the distance from one Z line to another in a sarcomere?
Sarcomere length
Which type of filaments are anchored at the Z lines?
F-actin
What is responsible for muscle contraction according to the sliding-filament model?
Sliding of thin filaments past thick filaments
What holds the thin and thick filaments together during muscle contraction?
Cross-bridges
What type of structure requires energy for the sliding of thin filaments past thick filaments?
Sarcomeres
What is the primary function of myosins in cellular events?
Muscle contraction
Which statement accurately describes the structure of myosins?
The globular head group binds actin and uses ATP hydrolysis for movement.
In what direction are most myosins motors directed?
Toward the positive end of actin filaments
What is a common function of Type II myosins?
Pulling arrays of actin filaments together
What is the role of light chains in myosins?
Regulating the ATPase for movement
What is a characteristic feature of myosin II molecules?
They bunch together in a staggered formation to make thick filaments.
What is the role of ATP in muscle contraction?
Binds to myosin
In skeletal muscle cells, what leads to muscle relaxation?
Decline in calcium levels due to ATP-dependent pumps
What is responsible for regulating the availability of myosin-binding sites on actin filaments?
Tropomyosin
Which event allows myosin to bind to actin filaments during muscle contraction?
Increase in calcium concentration causing tropomyosin shift
Which type of muscle contraction is responsible for involuntary contractions?
Smooth muscle
What are the dense bodies found in smooth muscles responsible for?
Anchoring actin and myosin filaments
What causes a conformational change in myosin in smooth muscle cells?
Myosin light-chain phosphorylation
What removes phosphate from the myosin light chain in smooth muscle cells to promote relaxation?
MLCP Myosin Light-Chain Phosphatase
Explore the mechanisms behind microfilament-based motility focusing on muscle contraction in skeletal muscle vs. smooth muscle, as well as the role of myosins in various cellular events such as cell movement, muscle contraction, and vesicle transport.
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