Cytoskeletal Filaments Structure and Dynamics

False (B)

Parallel actin filaments

<p>filamin</p> Signup and view all the answers

<p>Villin and Fimbrin = Cross-link actin into parallel bundles in microvilli Filamin and Spectrin = Web-forming/stabilizing proteins Myosin = Interacts with actin to produce movement Calmodulin = Calcium-binding messenger protein</p> Signup and view all the answers

<p>Tau (C)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>tropomyosin</p> Signup and view all the answers

<p>cofilin</p> Signup and view all the answers

<p>Tropomyosin (D)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>CapZ = Stabilizes the plus end of actin ARP complex = Stabilizes the minus end of actin Filaggrin = Bundles keratin filaments in the skin Plectin = Cross-links intermediate filaments to microtubules</p> Signup and view all the answers

<p>epidermolysis bullosa, muscular dystrophy, and neurodegeneration</p> Signup and view all the answers

<p>Stathmins (A)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>Both bind to and stabilize the minus end of a cytoskeletal element and promote nucleation.</p> Signup and view all the answers

<p>50-100</p> Signup and view all the answers

<p>MAP2 = Microtubules Villin = Microfilaments Plectin = Intermediate Filaments Formins = Microfilaments</p> Signup and view all the answers

<p>To anchor and stabilize the minus end of microtubules (C)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>A structure with spikes emanating out from one bright spot resembling a star, with the minus ends anchored at the center (MTOC) and plus ends growing outwards.</p> Signup and view all the answers

<p>right</p> Signup and view all the answers

<p>Gamma tubulin ring complexes (D)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>It helps to position the centrosome at its center and provides an internal coordinate system to properly position organelles.</p> Signup and view all the answers

<p>Centrosome = The microtubule organizing center (MTOC) Centrioles = Rod like structures positioned at right angles to each other within the centrosome matrix MT Aster = Star-like configuration of microtubules emanating from the MTOC Minus end of MT = The end that is anchored at the centrosome.</p> Signup and view all the answers

<p>Adding actin subunits to the growing end of the filament (B)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>plasma membrane</p> Signup and view all the answers

<p>stathmin</p> Signup and view all the answers

<p>It releases tubulin and enhances polymerization. (C)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>by exposing more plus ends</p> Signup and view all the answers

<p>Formin = Adds actin subunits to growing filament ends Profilin = Unlocks actin to make it available for polymerization Stathmin = Sequesters unpolymerized tubulin subunits Severing Proteins = Regulates the length and kinetic behavior of actin filaments</p> Signup and view all the answers

<p>Near the nucleus (C)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>providing directionality for transport</p> Signup and view all the answers

<p>plasma membrane</p> Signup and view all the answers

<p>The Minus end (A)</p> Signup and view all the answers

<p>Centrosomes (A)</p> Signup and view all the answers

<p>Centrosome = Located near the nucleus Plus end of microtubules in polarized cells = Oriented toward the basal side Minus end of microtubules in polarized cells = Oriented toward the apical side Actin nucleation = Occurs near the plasma membrane</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

A structure found in the center of animal cells. It acts as a microtubule organizing center (MTOC) and is crucial for the organization and formation of microtubule networks. The minus end of microtubules is anchored to the centrosome.

The plus end of a microtubule is the end that grows outwards from the centrosome. It is the more dynamic end, meaning it can grow or shrink faster than the minus end.

The minus end of the microtubule is anchored to the centrosome. It is more stable compared to the plus end.

A structure found within the centrosome. It appears as a pair of rod-like structures arranged at right angles to each other. They duplicate during cell division and move to opposite poles of the cell.

The process by which a cell divides into two identical daughter cells. During mitosis, the centrioles duplicate and move to opposite poles of the cell, playing a role in the separation of chromosomes.

A protein complex that forms ring-like structures within the centrosome. These rings are involved in the nucleation of microtubule assembly, or the initiation of microtubule growth.

The dynamic nature of microtubules is largely due to the activity at the plus end, where they can grow or shrink rapidly. The minus end is relatively stable and anchored to the centrosome.

The astral configuration of microtubules in animal cells is characterized by plus ends pointing outwards from the MTOC. This arrangement allows the centrosome to be positioned at the center of the cell and provides an internal coordinate system for organelle positioning.

The arrangement of microtubules (MTs) in a cell can vary depending on the cell type and stage of development. In dividing cells, MTs radiate outwards from the microtubule organizing center (MTOC), typically near the nucleus, pushing against the cell's edges and establishing a central direction for transport.

In differentiated cells, which have specialized functions, microtubules can have a different arrangement. They may not be directly connected to the MTOC and can be oriented in a specific direction to facilitate transport within the cell.

In polarized cells, which are specialized cells with an apical (top) and basal (bottom) surface, microtubule orientation is crucial for directed transport. The minus ends of MTs are positioned towards the apical side, while the plus ends point to the basal side.

Actin filaments, which are part of the cell's cytoskeleton, are often nucleated (formed) at the plasma membrane, the cell's outer boundary. This proximity allows actin to quickly respond to signals from the environment and participate in dynamic cell processes.

Actin filaments contribute to various structures on the cell surface, including microvilli (finger-like projections), filopodia (thin, long projections), lamellipodia (broad, sheet-like extensions), and even phagocytic cups, which engulf particles.

MAP2 is a microtubule-associated protein found in dendrites. It binds to microtubules at both ends, creating larger spacing between them compared to axonal microtubules.

Tau is a microtubule-associated protein located in axons. It binds to microtubules at both ends but creates smaller spacing between them compared to dendritic microtubules.

Tropomyosin is an elongated protein that stabilizes actin filaments by binding to 7 adjacent actin subunits. It prevents cofilin from destabilizing the filament.

Cofilin is a protein that destabilizes actin filaments by binding and twisting them more tightly. It prefers to bind to older, ADP-containing filaments.

CapZ is a protein that caps and stabilizes the plus end of actin filaments. It prevents further polymerization at the plus end.

The ARP complex stabilizes the minus end of actin filaments. It is essential for branching and the formation of actin networks.

Filaggrin is a protein that bundles keratin filaments in the outer layer of skin. It provides strength and toughness to the skin.

Plectin is a protein that cross-links intermediate filaments to microtubules and actin filament bundles. It helps maintain cell structure and stability.

Formin is a protein that acts like a spinning table top, adding actin subunits to the growing end of an actin filament.

Profilin, a protein that binds to actin monomers and competes with thymosin for available actin, is essential for adding actin to the growing filament.

Profilin is activated by extracellular signals, often through receptor tyrosine kinases, which triggers its release from the plasma membrane and allows it to bind to actin.

Stathmins are proteins that bind to tubulin dimers, preventing them from adding to growing microtubule filaments.

Phosphorylation of stathmins releases tubulin, allowing it to bind to microtubules and promoting microtubule polymerization.

Severing proteins break down existing long actin filaments into shorter filaments, accelerating the assembly of new filaments and increasing depolymerization.

Cancer cells often overexpress stathmins, leading to an increased rate of microtubule turnover, which contributes to changes in the morphology of cancer cells.

The plasma membrane serves as a location for profilin to bind to phospholipids and await activation by extracellular signals, ultimately driving actin polymerization at the cell surface.

Actin filaments are bundled into parallel arrays by crosslinking proteins like villin and fimbrin. These bundles form the core of microvilli, finger-like projections that increase surface area.

Filamins and spectrins are proteins that help create actin networks, which are more flexible and can change shape. These networks are important for cell movement and maintaining cell shape.

Filamin-deficient cancer cells have difficulty moving and spreading, suggesting that actin webs are critical for cell migration.

Spectrins provide flexibility and resilience to red blood cells, allowing them to squeeze through narrow blood vessels and return to their original shape.

Actin filaments are dynamic structures that can be assembled and disassembled rapidly. This property allows cells to change shape and move.

A protein involved in building microtubule networks, the minus end of a microtubule is anchored to the centrosome, which is the microtubule organizing center.

A protein complex that promotes the formation of branched actin filaments, they can bind to the sides of older actin filaments and nucleate new actin filament growth.

Cofilin can bind to old actin filaments (those with ADP bound to their subunits) more tightly than new actin filaments (those with ATP bound to their subunits), which makes it more likely to depolymerize old filaments.

Cells have a high concentration of actin monomers that can form a dynamic network of filaments. This allows the cell to rapidly remodel its cytoskeleton in response to stimuli and changes in the environment.

The centrosome is a microtubule organizing center (MTOC) which functions to organize microtubules. Once microtubules emerge from the centrosome they extend radially outward and probe the cell periphery. The centrosome moves to the center of the cell, indicating an equal distribution of microtubules around its periphery.