Actin Filaments and Polymerization Quiz

Long, helical polymers made of F-actin, approximately 7 nm in diameter.

Globular form of actin that polymerizes to form F-actin.

The end of an actin filament where growth occurs rapidly.

The end of an actin filament where disassembly occurs slowly.

Energy molecule required for the polymerization of G-actin.

A protein that interacts with actin filaments to facilitate movement.

A type of cytoskeleton that contains both actin and myosin filaments.

A structural unit found in muscle cells, responsible for muscle contraction.

The ability of actin filaments to change shape, forming bundles or networks.

The process of muscle contraction is regulated by the level of calcium ions.

A protein found in muscle fibers that is involved in regulating muscle contraction.

The regulation of muscle contraction in smooth muscle is controlled by phosphorylation of myosin light chains.

The process of adding a phosphate group to a molecule.

A protein chain that forms part of the myosin molecule.

The release of calcium from the sarcoplasmic reticulum (SR) triggers muscle contraction, while its reabsorption back into the SR leads to relaxation.

A sequence of events that links a nerve impulse to muscle contraction.

The process by which the arrival of an action potential at a motor neuron leads to the release of acetylcholine, initiating muscle contraction.

The process by which calcium binds to troponin, initiating a conformational change that uncovers the binding site of the myosin head on the actin filament.

The step in muscle contraction where the myosin head binds to actin, creating a cross-bridge.

The movement of myosin towards the center of the sarcomere, powered by ATP hydrolysis.

The process of restoring calcium levels in the SR, leading to muscle relaxation.

The process of forming a new actin filament from individual G-actin monomers.

The concentration of free G-actin monomers at which the rate of polymerization equals the rate of depolymerization, maintaining a steady state of filament length.

The process by which actin filaments maintain a constant length by adding monomers at the plus end while simultaneously losing monomers at the minus end.

Specialized proteins that bind to actin filaments and regulate their behavior, influencing polymerization, depolymerization, and organization.

A type of ABP that stabilizes actin filaments by binding along their sides.

An ABP that severs actin filaments and prevents their elongation by binding to the plus end.

A type of myosin that is responsible for muscle contraction.

A type of muscle tissue that is responsible for voluntary movement, attached to bones via tendons. Characterized by a striated appearance due to sarcomeres.

A type of muscle tissue that is involuntary and responsible for continuous heart contractions. Similar to skeletal muscle, but branched and interconnected by intercalated discs.

A type of muscle tissue that is involuntary and responsible for slower, sustained contractions in organs like the intestines and blood vessels. Not striated; involved in movement of internal organs.

The process by which muscle cells contract. It involves the sliding of actin filaments past myosin filaments.

A specialized cell junction that connects cardiac muscle cells, enabling the rapid propagation of action potentials and synchronized contraction.

A long, elastic protein that extends from the Z line to the M line in the sarcomere. It helps to maintain the structure of the sarcomere and provides elasticity to muscle fibers.

Projections from the surface of epithelial cells that increase surface area for absorption, particularly in the intestines. Formed by actin filaments.

In muscle contraction, the sliding filament model describes how actin and myosin filaments interact. Myosin heads attach to actin, pull them along, and detach, causing the muscle to shorten.

Tropomyosin is a protein that wraps around actin filaments, blocking myosin binding sites. This prevents muscle contraction unless calcium is present.

Troponin, a complex of proteins, regulates muscle contraction by binding to calcium ions. This binding causes a conformational change, removing tropomyosin from the actin filament, allowing myosin to bind and contraction to occur.

ATP, adenosine triphosphate, is a crucial energy source for muscle contraction. It helps to detach myosin from actin and reposition it for the next cycle of contraction.

The process of actin and myosin interacting and detaching to shorten a sarcomere, resulting in muscle contraction.

Myosin heads bind to actin filaments. When ATP binds to myosin, it detaches. ATP hydrolysis and repositioning of the myosin head occur. Pi and ADP are released, enabling the myosin head to bind to actin again.

In cell movement, lamellipodia are thin, sheet-like extensions of the cell membrane. These extensions are used to sense the environment and stick to a surface, allowing the cell to move forward.

Cell movement involves a coordinated process of protrusion, attachment, and retraction. Protrusion extends lamellipodia, attachment links these extensions to the support, and retraction detaches the rear of the cell to allow forward movement.

A large protein that binds to actin filaments, regulating their length and contributing to the structure and stability of the sarcomere.

Proteins that cap the ends of actin filaments, ensuring their length remains constant. They include Cap Z and Tropomodulin.

The process where actin filaments slide past myosin filaments, causing the sarcomere to shorten and result in muscle contraction.

Structures involved in cell adhesion, migration, and mechanical sensing. They are found in non-muscle cells, but are similar in structure to muscle sarcomeres.

Cell membrane protrusions that play a role in cell migration, such as phagocytosis or tissue invasion.

The process of a cell moving from one point to another, involving actin polymerization, adhesion, and protrusion.

The formation of focal contacts, which are specialized structures that link the cytoskeleton to the extracellular matrix and facilitate cell migration.

The process of actin polymerization that drives the leading edge of a cell forward during migration.

The interaction of different actin filaments to form a complex network, contributing to cellular shape and functions such as cell division and migration.

A protein complex responsible for regulating the polymerization of actin filaments. It is involved in cell migration and other cellular processes.

A molecule that binds to actin filaments, changing their structure and function. These molecules can regulate actin filament dynamics, including polymerization and depolymerization.