Cytoskeleton and ECM Quiz
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Questions and Answers

Which structure is responsible for connecting muscle fibers and transmitting force in skeletal muscle?

  • H zone
  • Z disc (correct)
  • M line
  • A band

What role does calcium play in muscle contraction?

  • It binds to troponin C to facilitate contraction. (correct)
  • It breaks down ATP.
  • It is stored in the sarcomere.
  • It directly interacts with myosin.

What are integrins primarily involved in?

  • Cell adhesion to the extracellular matrix (correct)
  • Actin filament growth
  • Cell signaling pathways
  • ATP synthesis

Which type of junction is primarily responsible for maintaining strong adhesion between adjacent cells in tissues?

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

What characterizes the H zone in a sarcomere?

<p>It contains only myosin filaments. (B)</p> Signup and view all the answers

What is the function of formin in relation to actin filaments?

<p>It nucleates actin filament formation. (B)</p> Signup and view all the answers

Which part of the sarcomere is responsible for the overall length and strength of muscle contraction?

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

Which of the following statements about ATP and muscle contraction is true?

<p>ATP powers the movement of myosin on actin. (A)</p> Signup and view all the answers

What is the primary role of the I band during muscle contraction?

<p>It is where the thin filaments slide during contraction. (B)</p> Signup and view all the answers

Which filament structure provides the site for muscle contraction by allowing sliding interactions?

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

What is the primary role of integrins in cellular functions?

<p>Anchor the cell to the extracellular matrix (C)</p> Signup and view all the answers

What role does formin play in the assembly of actin filaments?

<p>Facilitates nucleation of new actin filaments (B)</p> Signup and view all the answers

In what cellular context is calcium binding to TNC critical?

<p>Triggering muscle contraction (C)</p> Signup and view all the answers

What is the primary function of stress fibers within a cell?

<p>Maintain cell shape and stability (B)</p> Signup and view all the answers

Why is the M Line significant in skeletal muscle structure?

<p>It anchors the thick filaments in the sarcomere (C)</p> Signup and view all the answers

What physiological event occurs in muscle cells in the absence of calcium?

<p>Inhibition of actin-myosin interaction (B)</p> Signup and view all the answers

Which region of the sarcomere can be characterized as the area with no overlapping filaments?

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

What is the significance of the I band during muscle contraction?

<p>It shortens as the muscle contracts (D)</p> Signup and view all the answers

What is the primary function of cadherins at cell-cell junctions?

<p>Anchor cells together in tissues (C)</p> Signup and view all the answers

What is the main role of stress fibers within a cell?

<p>Providing structural support and stiffness. (A)</p> Signup and view all the answers

Which of the following is essential for the sliding mechanism between actin and myosin filaments?

<p>Formation of cross-bridges. (A), Binding of calcium to TNC. (C)</p> Signup and view all the answers

How does the presence of calcium influence muscle contraction?

<p>It binds to troponin C, allowing myosin to bind to actin. (D)</p> Signup and view all the answers

What structural feature of the sarcomere is characterized by regions of overlapping thick and thin filaments?

<p>A band. (C)</p> Signup and view all the answers

Which component is primarily involved in connecting the extracellular matrix to the cytoskeleton?

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

What occurs at the M Line of the sarcomere?

<p>The center where thick filaments are anchored. (D)</p> Signup and view all the answers

Which filament structure is primarily composed of G-actin monomers?

<p>Actin filaments. (D)</p> Signup and view all the answers

What is the significance of the Z disc in muscle fibers?

<p>It marks the boundary between adjacent sarcomeres. (B)</p> Signup and view all the answers

Which process is triggered upon the binding of calcium to troponin?

<p>Exposing binding sites on the actin filaments. (D)</p> Signup and view all the answers

What happens to muscle contraction in the absence of ATP?

<p>Cross-bridges will remain attached and lead to stiffness. (B)</p> Signup and view all the answers

What is the basic role of G-actin in muscle contraction?

<p>Forms thin filaments (B)</p> Signup and view all the answers

What is the primary purpose of the Z disc in muscle fibers?

<p>Anchors actin filaments (D)</p> Signup and view all the answers

How do integrins function within the extracellular matrix?

<p>Connect the cytoskeleton to the ECM (C)</p> Signup and view all the answers

What does the H zone represent in a sarcomere?

<p>The area of non-overlapping myosin only (C)</p> Signup and view all the answers

What is the role of calcium in muscle contraction?

<p>It activates troponin to allow actin-myosin interactions (B)</p> Signup and view all the answers

What primary structures contribute to the formation of focal adhesions?

<p>Integrins and actin filaments (A)</p> Signup and view all the answers

Which two structures are essential for the sliding mechanism of muscle contraction?

<p>Actin and myosin filaments (D)</p> Signup and view all the answers

What is a function of the adherens junctions?

<p>Provide mechanical strength between cells (A)</p> Signup and view all the answers

The M Line in a sarcomere is responsible for holding together the I band.

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

Calcium and ATP are both essential for muscle contraction to occur.

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

The Z disc in muscle fibers is responsible for producing calcium.

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

The H zone in a sarcomere is characterized by overlapping filaments.

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

Integrins play a key role in connecting the cytoskeleton to the extracellular matrix.

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

Stress fibers are primarily composed of myosin filaments.

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

Formins promote the nucleation and polymerization of actin filaments.

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

During muscle contraction, the A band remains the same length.

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

G-actin monomers do not play a significant role in muscle fiber contraction.

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

The I band in a sarcomere represents the area where actin and myosin are overlapping.

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

The basic unit of muscle contraction is called a ______.

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

In skeletal muscle, the ______ zone is where thick and thin filaments overlap.

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

Calcium binds to ______ to initiate muscle contraction.

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

During muscle contraction, myosin heads utilize ______ for energy.

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

The ______ disc anchors the actin filaments in a sarcomere.

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

The ______ line holds the thick filaments together in the center of the sarcomere.

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

The ______ fibers are primarily responsible for providing mechanical support within the cell.

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

In the absence of calcium, muscle contraction cannot occur because ______ remains bound to actin.

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

Integrins are crucial for ______ the extracellular matrix to the cytoskeleton.

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

The ______ zone is characterized by the absence of overlapping thick and thin filaments.

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

Match the components of the sarcomere with their descriptions:

<p>I band = Region where thin filaments slide past each other A band = Entire filament length including overlapping regions H zone = Region where there is no overlapping of filaments Z disc = Structure that anchors thin filaments together</p> Signup and view all the answers

Match the cellular structures with their primary functions:

<p>G-actin = Monomeric unit of actin filaments Formins = Facilitators of actin filament nucleation Integrins = Connectors between ECM and cytoskeleton Cadherins = Mediators of cell-cell adhesion in tissues</p> Signup and view all the answers

Match the types of muscle contraction with their requirements:

<p>Calcium = Facilitates binding to troponin for contraction ATP = Energy source for myosin movement on actin Stress fibers = Support cell shape and motility Focal adhesions = Connect the cell to ECM for force transmission</p> Signup and view all the answers

Match the regions of the sarcomere with their characteristics:

<p>M Line = Anchors thick filaments in place Z disc = Defines the boundary of a sarcomere A band = Area containing both thick and thin filaments H zone = Area of the A band not occupied by thin filaments</p> Signup and view all the answers

Match the roles of calcium in muscle function to their effects:

<p>Binds to TNC = Initiates contraction process in muscle cells In absence = Prevents muscle contraction Calcium influx = Triggers signaling for muscle activation Calcium release = Facilitates sliding filament mechanism</p> Signup and view all the answers

Match the parts of muscle contraction to their roles:

<p>Thin filaments = Composed of actin and responsible for contraction Thick filaments = Composed of myosin and interact with thin filaments Sliding mechanism = Relies on ATP and calcium presence Tension generation = Result of cross-bridge cycling between actin and myosin</p> Signup and view all the answers

Match the types of filaments to their associated proteins:

<p>Actin filaments = Formed from G-actin monomers Myosin filaments = Motor proteins that pull on actin Focal adhesions = Formed via integrin interactions Stress fibers = Rich in actin for structural support</p> Signup and view all the answers

Match the concepts related to actin dynamics:

<p>Nucleation = Initial stage of filament assembly Polarity = Describes the orientation of actin filaments Treadmilling = Dynamic equilibrium in filament growth Capping proteins = Regulate filament length and stability</p> Signup and view all the answers

Match the factors influencing muscle contraction to their descriptions:

<p>Calcium availability = Critical for muscle activation ATP levels = Necessary for myosin cross-bridge cycling Fiber type = Determines contraction speed and endurance Signal transduction = Relays messages for contraction onset</p> Signup and view all the answers

Match the junction types with their functions:

<p>Adherens junctions = Strengthen cell-cell adhesion Tight junctions = Prevent paracellular transport Desmosomes = Provide structural integrity to tissue layers Gap junctions = Facilitate intercellular communication</p> Signup and view all the answers

Flashcards

G-actin filaments

Actin filaments are made up of G-actin monomers that assemble into long, helical chains. These filaments are involved in various cellular processes, including cell movement, shape maintenance, and muscle contraction.

Formin

Formin is a protein that helps to assemble actin filaments. It acts as a nucleator, initiating the assembly of new actin filaments in specific directions.

Focal adhesions

Focal Adhesions are specialized structures that connect the cytoskeleton inside the cell to the extracellular matrix outside the cell. They are important for cell adhesion, migration, and signaling.

Integrins

Integrins are transmembrane proteins that connect the cytoskeleton to the extracellular matrix. They play a crucial role in cell signaling and mediating interactions with other cells.

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Stress fibers

Stress fibers are bundles of actin filaments that help to maintain cell shape and allow cells to withstand mechanical stress. They are often found in cells that are undergoing migration or adhering to a surface.

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Adherens junctions

Adherens junctions are cell-cell junctions that connect cells together through cadherins. These junctions are important for maintaining tissue integrity and cell communication.

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Cadherins

Cadherins are transmembrane proteins that bind to each other across the space between two adjacent cells, contributing to the formation of adherens junctions.

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Sarcomere

A sarcomere is the fundamental unit of muscle contraction. It contains both thin (actin) and thick (myosin) filaments that slide past each other during contraction, shortening the sarcomere.

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I band

The I band of a sarcomere is the region where only thin filaments (actin) are present. It shortens during muscle contraction as the filaments slide past each other.

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M line

The M line of a sarcomere is a protein structure that anchors the thick filaments (myosin) in the center of the sarcomere. It helps to maintain the structural integrity of the sarcomere.

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What are actin filaments composed of?

Actin filaments are made up of G-actin monomers that assemble into long, helical chains. These filaments are involved in various cellular processes, including cell movement, shape maintenance, and muscle contraction.

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What protein helps build actin filaments?

Formin is a protein that helps assemble actin filaments by acting as a nucleator, initiating the formation of new filaments in specific directions.

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What connects the cytoskeleton to the ECM?

Focal adhesions are specialized structures that connect the cytoskeleton inside the cell to the extracellular matrix outside the cell. They are important for cell adhesion, migration, and signaling.

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What proteins bridge the cytoskeleton and the ECM?

Integrins are transmembrane proteins that connect the cytoskeleton to the extracellular matrix. They play a crucial role in cell signaling and mediating interactions with other cells.

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What are bundles of actin filaments called that resist stress?

Stress fibers are bundles of actin filaments that help maintain cell shape and allow cells to withstand mechanical stress. They are often found in cells that are undergoing migration or adhering to a surface.

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What type of junction connects cells with cadherins?

Adherens junctions are cell-cell junctions that connect cells together through cadherins. These junctions are important for maintaining tissue integrity and cell communication.

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What proteins are responsible for cell-cell adhesion in adherens junctions?

Cadherins are transmembrane proteins that bind to each other across the space between two adjacent cells, contributing to the formation of adherens junctions.

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What is the basic unit of muscle contraction?

A sarcomere is the fundamental unit of muscle contraction. It contains both thin (actin) and thick (myosin) filaments that slide past each other during contraction, shortening the sarcomere.

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What region in a sarcomere contains only actin filaments?

The I band of a sarcomere is the region where only thin filaments (actin) are present. It shortens during muscle contraction as the filaments slide past each other.

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What structure anchors the thick filaments in the center of a sarcomere?

The M line of a sarcomere is a protein structure that anchors the thick filaments (myosin) in the center of the sarcomere. It helps to maintain the structural integrity of the sarcomere.

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What protein helps assemble actin filaments?

Formin initiates the assembly of new actin filaments in specific directions, acting as a nucleator.

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What links the cytoskeleton to the ECM?

Focal adhesions are structures connecting the cytoskeleton inside the cell to the extracellular matrix outside.

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What are bundles of actin filaments that resist stress called?

Stress fibers are bundles of actin filaments that help maintain cell shape and withstand mechanical stress.

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What proteins bridge the cytoskeleton and ECM?

Transmembrane proteins that bridge the cytoskeleton to the ECM, playing a crucial role in attaching cells to their surroundings and cell signaling.

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What is Formin?

A protein that helps to assemble actin filaments by acting as a nucleator, initiating the assembly of new filaments in specific directions.

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What are focal adhesions?

Specialized structures that connect the cytoskeleton inside the cell to the extracellular matrix outside the cell. They are important for cell adhesion, migration, and signaling.

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What are integrins?

Transmembrane proteins that connect the cytoskeleton to the extracellular matrix. They play a crucial role in cell signaling and mediating interactions with other cells.

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What are stress fibers?

Bundles of actin filaments that help to maintain cell shape and allow cells to withstand mechanical stress. They are often found in cells that are undergoing migration or adhering to a surface.

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What are adherens junctions?

Cell-cell junctions that connect cells together through cadherins. These junctions are important for maintaining tissue integrity and cell communication.

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What are cadherins?

Transmembrane proteins that bind to each other across the space between two adjacent cells, contributing to the formation of adherens junctions.

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What is a Sarcomere?

The fundamental unit of muscle contraction. It contains both thin (actin) and thick (myosin) filaments that slide past each other during contraction, shortening the sarcomere.

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What is the I band?

The region where only thin filaments (actin) are present. It shortens during muscle contraction as the filaments slide past each other.

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What is the M line?

A protein structure that anchors the thick filaments (myosin) in the center of the sarcomere. It helps to maintain the structural integrity of the sarcomere.

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What is the A band?

The entire filament where the regions are overlapping. It remains constant during muscle contraction.

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What are actin filaments?

Actin filaments are made of G-actin monomers assembling into long, helical chains. Vital for cell movement, shape, and muscle contraction.

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What is the role of formin?

Formin is a protein that helps build actin filaments by acting as a nucleator. It starts the assembly of new filaments.

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How do integrins contribute to cell signaling?

Integrins are transmembrane proteins that connect the cytoskeleton to the extracellular matrix. They play a crucial role in cell signaling and mediating interactions with other cells.

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Where is the I band located?

The I band of a sarcomere is the region where only thin filaments (actin) are present. It shortens during muscle contraction as the filaments slide past each other.

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What is the role of the M line?

The M line of a sarcomere is a protein structure that anchors the thick filaments (myosin) in the center of the sarcomere. It helps maintain the structural integrity of the sarcomere.

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What are actin filaments made of?

G-actin, a globular protein monomer, forms long chains that make up actin filaments, crucial for various cellular functions.

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What junctions connect cells through cadherins?

Adherens junctions connect cells together through cadherin proteins, maintaining tissue integrity and cell communication.

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Study Notes

Cytoskeleton

  • Actin Filaments:

    • Assembled into higher-order structures (bundles or networks) within cells.
    • Actin-binding proteins influence actin filament function.
    • Myosin motors mediate muscle contraction, and intracellular transport.
    • Actin filament assembly and disassembly are regulated by ATP and specific proteins.
    • Actin-binding proteins and how they influence the structural organization of actin networks are explained with considerations for specific examples for cellular movement and myosin functions..
    • There are specific experimental techniques to visualize actin filament dynamics, including using ATP and specific proteins and techniques for visualizing cellular movement and myosin functions..
    • Specific examples of actin filament contributions to cellular movement in different cell types are given, including details of myosin's roles in muscle contraction and intracellular transport, along with experimental techniques for visualization.
    • The relationship between actin-binding proteins and the dynamics of actin filament assembly is explained with consideration of specific examples for cellular movement and myosin functions, along with techniques for visualization.
    • Examples of how actin filaments contribute to cellular movement in different cell types are provided, including details of myosin's roles in muscle contraction and intracellular transport, along with experimental techniques for visualization. A clarification of the roles of myosin in muscle contraction and intracellular transport will be included. Techniques and details on visualizing cellular movement and myosin functions will further be elucidated.

  • Microtubules:

    • Assembled microtubules
    • Microtubule-associated proteins (MAPs) organize microtubules.
    • Microtubule motor proteins facilitate intracellular transport, including types of myosin, and their roles.
    • Mechanisms and factors regulating microtubule stability, like dynein and kinesin, are described.
    • Motor proteins like kinesin and dynein coordinate intracellular transport.
    • Factors determining microtubule polarity are explained and why polarity as important is given. Processes like polymerization and depolymerization are discussed and clarified.
    • How microtubule motor proteins are selectively recruited for intracellular transport is noted, along with how disruptions in microtubule assembly contribute to disorders, and real-world examples demonstrating the critical role of MAPs in disease and therapy.
    • Real-world examples demonstrating the critical role of MAPs in disease and therapy are provided, and details of processes like polymerization and depolymerization are examined and clarified. Processes involved in polymerization and depolymerization are expanded upon.

  • Intermediate Filaments:

    • Described assembly process, primary roles in structure and function.
    • Defects in these filaments associate with diseases (various types of IFs and function are specified).
    • Different types of intermediate filaments, and their roles in cellular processes, are discussed with details about various proteins.
    • Factors that regulate the assembly or disassembly of intermediate filaments during cell division are explained.

  • Cell-Cell and Cell-ECM Contacts:

    • Compared focal adhesions and hemidesmosomes, noting specific structural and functional differences, detailed process are included.
    • Differences between adherens junctions and desmosomes, also noted in structure and function, including the proteins involved are elaborated.
    • Integrins and cadherins are involved in signaling between cells and the cell's interior during adhesion, with examples discussed, and methods to study them in labs. details on each protein and structure of junctions are elaborated.
    • Actin, integrins, and intermediate filaments are involved in ECM interactions.
    • The differences in signaling pathways activated by focal adhesions versus adherens junctions, as well as the structural and functional differences between hemidesmosomes and desmosomes, are described, and diseases/disorders due to defects are discussed, including examples for clarity.

Extracellular Matrix (ECM)

  • Matrix Components:
    • Three major components of the ECM (collagen, proteoglycans, and glycosaminoglycans), and their specific roles in tissues are highlighted, with specific details of each.
    • Properties relating to tissue hydration and resistance to compression, with examples given, elaborated.
    • The roles of each component are detailed, including how GAGs and proteoglycans influence tissue hydration and resistance to compression, along with their influences on mechanical properties and signaling, further details are provided.
  • Adhesion Proteins:
    • Roles of fibronectin and laminins in the ECM, including details about cell-ECM interactions and their importance, clarified and elaborated.
    • How integrins mediate cell-matrix interactions.
    • Other adhesion proteins are noted and their functions are discussed with more details.
    • Role of ECM structural proteins and proteoglycans in tissue mechanical properties and signaling interactions with growth factors are explained.
    • The roles of fibronectin and laminins in tissue repair and regeneration are detailed with examples.
    • ECM composition changes during development or disease progression are described, along with ways to study ECM remodeling in living tissues, using examples.
    • Techniques for studying ECM remodeling in living tissues are detailed.
    • ECM structural proteins, such as collagen, influence tissue mechanical properties; proteoglycans' role in signaling and interactions with growth factors is elaborated.
    • Fibronectin and laminins play different important roles in tissue repair and regeneration, and methods/techniques for studying ECM remodeling in living tissues are given with details. Other relevant adhesion proteins are further elaborated. More examples are described to illustrate the role of ECM remodeling, particularly in tissue repair and regeneration.

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Description

Test your knowledge on the cytoskeleton and extracellular matrix (ECM) components. This quiz covers actin filaments, microtubules, intermediate filaments, and the various roles of ECM's matrix components. Understand the structural and functional differences of cell junctions and adhesion proteins.

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