Extracellular Matrix Function and Components

Questions and Answers

What is one function of the primary cell wall?

Mediates adhesion between organelles

Allows for cell expansion (correct)

Enhances tissue waterproofing

Provides insulation to tissues

What role does lignin play in plant tissues?

Enhances rigidity and waterproofing (correct)

Inhibits cell division

Induces cell migration

Provides compression resistance

Which of the following statements about plasmodesmata is true?

They are responsible for cell-to-cell adhesion.

They are found exclusively in animal cells.

They are integral to the Supracellularity Hypothesis. (correct)

They allow movement of large proteins only.

What is a characteristic of secondary cell walls?

Thicker and more rigid than primary cell walls Signup and view all the answers

How do cell walls contribute to tissue and organ specialization?

By being highly dynamic and remodeled Signup and view all the answers

What is the primary component of pectin in cell walls?

Polysaccharides Signup and view all the answers

What function does the cell wall serve regarding signaling molecules?

It acts as a long-term reservoir. Signup and view all the answers

What process is affected by integrin switching during cell migration?

Directional cell movement Signup and view all the answers

What is the role of Na+-driven glucose symport in glucose transport?

It actively transports glucose into the epithelial cell. Signup and view all the answers

How do tight junctions contribute to epithelial function?

They seal neighboring cells to prevent leakage of water-soluble molecules. Signup and view all the answers

What occurs at the basolateral domain during glucose transport?

Glucose carriers mediate facilitated diffusion from the cell to the extracellular fluid. Signup and view all the answers

What is a key requirement for the Na+-glucose symport during glucose transport?

It must not migrate to the basolateral surface of the cell. Signup and view all the answers

Which epithelial structures are primarily influenced by tight junctions?

The intestines and urinary bladder. Signup and view all the answers

What is the primary function of occluding junctions?

Seal the space between epithelial cells Signup and view all the answers

Which type of junction is classified as a communicating junction?

Gap junctions Signup and view all the answers

Which protein is crucial for stability and barrier function in tight junctions?

Occludin Signup and view all the answers

Which of the following proteins determines the barrier properties of the cell contacts in tight junctions?

Claudin Signup and view all the answers

Which junction type encircles the apical end of each cell in epithelial sheets?

Tight junctions Signup and view all the answers

What is the primary role of cadherins in animal cells?

Mediate cell-cell adhesion Signup and view all the answers

Which protein serves as scaffolding in the assembly of tight junctions?

ZO proteins Signup and view all the answers

What type of junction is characterized by an anastomosing network of protein strands?

Occluding junctions Signup and view all the answers

Which type of intercellular junction is specifically designed for attachment to intermediate filaments?

Desmosomes Signup and view all the answers

Which of the following is a role of cingulin in intercellular junctions?

Regulating gene expression Signup and view all the answers

What is the primary role of linker molecules in the ECM?

To connect collagen and proteoglycans with each other and with the plasma membrane Signup and view all the answers

Which mechanism allows ECM proteins to accumulate adjacent to target tissues?

Local synthesis in the target tissue Signup and view all the answers

What structural feature is common to fibronectin?

Two nearly identical polypeptide chains Signup and view all the answers

How do ECM components change as development progresses?

They are restricted in their expression to certain developing tissues Signup and view all the answers

What is the primary function of cellulose in plant cells?

To provide tensile strength Signup and view all the answers

Which protein is known to link microfibrils together in the extracellular matrix?

Extensins Signup and view all the answers

What does encapsulation of ECM components refer to?

The accumulation of proteins through receptor-dependent interactions Signup and view all the answers

Which statement best describes hemicellulose?

A network-forming polysaccharide that links microfibrils in plants Signup and view all the answers

What characteristic distinguishes the cell walls of different organisms?

The specific composition of polysaccharides and proteins Signup and view all the answers

What role does signaling play in cell differentiation with respect to ECM interaction?

It prolongs the signaling of other pathways necessary for differentiation Signup and view all the answers

What is the primary arrangement of septate junctions in epithelial cells?

Parallel rows with regular periodicity Signup and view all the answers

Which statement about connexons is true?

Connexons hold interacting plasma membranes at a fixed distance. Signup and view all the answers

How do gap junctions primarily function between cells?

By facilitating cell-cell communication Signup and view all the answers

What factors can cause gap junctions to close?

High levels of calcium and low pH in the cytosol Signup and view all the answers

What characteristic is common to most connexin disorders?

They are predominantly autosomal dominant. Signup and view all the answers

Study Notes

Linker Molecules

Connect collagen and proteoglycans in the extracellular matrix (ECM) and with the plasma membrane via fibronectin and laminin, which are adhesive glycoproteins.
Contain multiple domains that serve as binding sites for other ECM components and cell surface receptors.
Accumulate in target tissues through local synthesis, migration of cells, or distant secretion followed by capture.

Fibronectin

Composed of two nearly identical polypeptide chains linked by disulfide bonds.
Functions in ECM assembly at specific sites within the developing organism.
Accumulation can occur via receptor-dependent or independent mechanisms, requiring interaction with proteins on target tissues.

ECM and Development

ECM composition evolves throughout the development of an organism.
Certain ECM components are localized to specific developing tissues.
Interaction with the ECM is crucial for signaling pathways that promote cell differentiation.

ECM of Plant Cells

Contains cell wall (CW) components such as microfibrils of cellulose embedded in polysaccharide and protein matrices.
Functions of the CW include providing rigidity, serving as a permeability barrier and protecting cells from damage and infection.

Cell Wall Components

Cellulose: A glucose-based polysaccharide contributing tensile strength.
Hemocellulose & Extensins: Link microfibrils into a network, facilitating cell expansion and structure.
Pectin: Polysaccharide that aids in adhesion and forms matrix structures for support.
Lignin: Complex polymer present in woody tissues offering enhanced rigidity and waterproofing.

Cell Wall Structure

Primary CW: Thin wall formed during cell division, allowing expansion.
Secondary CW: Thicker and more rigid, formed post-growth, often with high cellulose content and potential lignin.
Plasmodesmata serve as cytoplasmic bridges connecting adjacent plant cells, allowing transport of solutes and regulatory molecules.

Cell Junctions

Occluding Junctions: Seal epithelial cells, preventing leakage of water-soluble molecules.
- Tight Junctions: Present in vertebrates, contribute to barrier function and segmentation of membrane domains.
- Septate Junctions: Found in invertebrates, form continuous bands around epithelial cells.

Proteins Involved in Tight Junctions

Occludin: Crucial for junction stability and barrier integrity.
Claudin: Determines barrier characteristics between cells.
ZO Proteins: Scaffolding proteins that aid in the structural organization of junctions.
Cadherins: Mediate cell adhesion and are essential for tissue morphogenesis and stability.

Functions of Junctions

Tight junctions prevent free passage of solutes, creating barriers in tissues like the intestinal epithelium.
Localize and constrain transport proteins to their respective membrane domains, ensuring proper function and signaling within cells.

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Description

Explore the roles of linker molecules, fibronectin, and the extracellular matrix (ECM) in organism development. This quiz covers the composition, functions, and interactions of ECM components and their significance in signaling pathways. Understand how ECM evolves and its impact on cell differentiation.