Extracellular Matrix and Tissue Functions
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Questions and Answers

The ______ provides structural integrity to connective tissues.

extracellular matrix

The ______ serves as a scaffold for cell organisation in tissues.

basal lamina

MMPs are used by dendritic cells to degrade ______.

extracellular matrix

The ECM can immobilize ______ gradients, influencing cell migration.

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

Components of the ECM include ______, fibrous proteins, and adhesive glycoproteins.

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

The ECM regulates cell ______, polarity, differentiation, and function.

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

The ECM provides resistance to compressive forces and elasticity, important for ______ tissues.

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

Different forms and arrangements of ECM components result in varying ______ properties among tissues.

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

The basal lamina connects the epidermis to the ______.

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

Basal lamina acts as a ______ for tissue regeneration.

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

One of the functions of the basal lamina is to determine cell ______.

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

Fibroblasts and chondroblasts are types of cells that ______ extracellular matrix components.

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

Matrix metalloproteases (MMPs) are involved in the ______ of the extracellular matrix.

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

Cell surface localization of proteases, such as MMP-14, is essential for their ______.

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

The extracellular matrix can be oriented by cells such as ______.

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

Cellular proteases are implicated in processes like inflammation and ______ invasion.

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

Laminin is a heterotrimer made up of , , and ______ chains.

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

The extracellular matrix is organized by cells that secrete ______ fibrils.

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

The outermost layer of skin is called the ______.

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

In connective tissues, the ______ determines the tissue’s physical properties.

<p>extracellular matrix (ECM)</p> Signup and view all the answers

Tendons are characterized by their ropelike structure and high ______ strength.

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

Blood vessel walls are described as resilient and ______.

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

Cartilage provides both tensile strength and ______ properties.

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

Bone tissue is known for being rigid and ______.

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

Elements such as ______ polysaccharide chains are important components of the extracellular matrix.

<p>glycosaminoglycan (GAG)</p> Signup and view all the answers

Fibrous proteins like collagen and ______ provide structural integrity to tissues.

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

Adhesive ______ act as adapters in the extracellular matrix.

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

The vitreous body of the eye consists of a transparent, jelly-like ______.

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

Type IX binds type II fibrils in ______

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

Elastic fibres primarily consist of ______

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

Fibronectin helps attach cells to the ______

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

The basal lamina is a thin, tough, flexible sheet of ______

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

Elastic fibres are also covered in ______ made from glycoproteins.

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

The ______ provides structural support and a medium for cell signaling.

<p>extracellular matrix</p> Signup and view all the answers

The ______ is a thin layer of ECM that supports epithelial cells.

<p>basal lamina</p> Signup and view all the answers

Remodeling and degradation of the ECM are essential for ______ during development.

<p>tissue remodeling</p> Signup and view all the answers

The ECM consists of proteins and polysaccharides, including ______, which provides tensile strength.

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

Cellular components in the ECM like ______ play a crucial role in cell communication.

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

Cell adhesion is particularly important in ______ tissues, where cells are tightly bound.

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

Cell-matrix adhesions enable cells to interact with the ______ surrounding them.

<p>extracellular matrix</p> Signup and view all the answers

Adhesion molecules allow cells to adhere to each other and the ______.

<p>extracellular matrix</p> Signup and view all the answers

In connective tissues, there are few cells and a ______ amount of ECM components.

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

Cell adhesion mechanisms are critical for the ______, development, function, and dynamics of tissues.

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

What is a primary role of the basal lamina?

<p>Providing selective barrier function</p> Signup and view all the answers

Which of the following is NOT a feature of the extracellular matrix?

<p>Secretion by adipose tissue</p> Signup and view all the answers

What type of chains compose the structure of laminin?

<p>α, β, and γ chains</p> Signup and view all the answers

What cellular process involves matrix metalloproteases (MMPs) during development?

<p>ECM remodelling and degradation</p> Signup and view all the answers

How do fibroblasts contribute to the extracellular matrix?

<p>By secreting ECM components and applying tension</p> Signup and view all the answers

What role does the extracellular matrix (ECM) play in tissues?

<p>It serves as a scaffold that contributes to tissue structure and function.</p> Signup and view all the answers

How do cell adhesion molecules contribute to cellular functions?

<p>They enable communication between cells in the immune system.</p> Signup and view all the answers

What characterizes epithelial tissues in terms of cell organization?

<p>They are comprised of sheets of tightly bound cells with minimal ECM.</p> Signup and view all the answers

Which statement is true regarding connective tissues?

<p>They are characterized by a rich presence of ECM with few cells.</p> Signup and view all the answers

What is a key feature of the extracellular matrix's role in cellular signaling?

<p>It provides a medium for cell signaling and communication.</p> Signup and view all the answers

Which types of adhesion are primarily found in epithelial tissues?

<p>Cell-cell adhesions linked to the cytoskeleton and some ECM.</p> Signup and view all the answers

How do cell-matrix adhesions function in connective tissues?

<p>They enable interaction between cells and the surrounding ECM.</p> Signup and view all the answers

Which statement correctly describes GAGs?

<p>One of the sugars in GAGs is always an amino sugar.</p> Signup and view all the answers

What is a characteristic feature of hyaluronan?

<p>It can be up to 25,000 disaccharide units long.</p> Signup and view all the answers

Which of the following groups is NOT a type of GAG?

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

What role do the highly negatively charged groups in GAGs serve?

<p>To attract water and create pressure.</p> Signup and view all the answers

Which feature is commonly associated with all GAGs?

<p>They are linear and unbranched.</p> Signup and view all the answers

In the context of proteoglycan synthesis, what happens to the linker added?

<p>It facilitates the attachment of polysaccharide chains.</p> Signup and view all the answers

What is the primary reason for the highly extended conformation of GAGs?

<p>To provide extensive surface area for hydration.</p> Signup and view all the answers

Which GAG is noted for being non-sulphated?

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

What is a common function of ECM components like fibrinogen and fibronectin?

<p>To facilitate cell adhesion.</p> Signup and view all the answers

What is the carbohydrate composition range of glycoproteins by weight?

<p>1-60%</p> Signup and view all the answers

What is the primary function of collagen α-chains?

<p>To create triple helices for structural support</p> Signup and view all the answers

What is a characteristic feature of fibril-associated collagens?

<p>They have non-helical domains that increase flexibility</p> Signup and view all the answers

Which amino acids commonly appear in the collagen backbone structure?

<p>Glycine, proline, and hydroxyproline</p> Signup and view all the answers

What factors influence the organization of collagen fibrils in connective tissue?

<p>The binding of fibril-associated collagens to other ECM molecules</p> Signup and view all the answers

What is the approximate diameter of collagen fibrils?

<p>0.5-3 µm</p> Signup and view all the answers

What is a defining characteristic of proteoglycans compared to glycoproteins?

<p>They have a higher carbohydrate content, often up to 95%</p> Signup and view all the answers

How do collagen trimers self-assemble?

<p>Into fibrils</p> Signup and view all the answers

What is the percentage of total protein mass in mammals that collagen represents?

<p>25%</p> Signup and view all the answers

What role do covalent crosslinks play in collagen fibrils?

<p>They reinforce the structure and stability</p> Signup and view all the answers

What is the primary component of elastic fibers that provides resilience?

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

Which fibrous protein is specifically associated with binding type I fibrils in tendons?

<p>Type XII</p> Signup and view all the answers

What role does fibronectin play in the extracellular matrix?

<p>Attaches cells to the ECM</p> Signup and view all the answers

What structure does the basal lamina provide in tissues?

<p>Support and adhesion</p> Signup and view all the answers

Which of the following describes the structure of elastic fibers?

<p>Formed by crosslinked elastin and microfibrils</p> Signup and view all the answers

What characteristic of collagen fibrils contributes to their function in the body?

<p>Tensile strength</p> Signup and view all the answers

What is a function of the microfibrils found within elastic fibers?

<p>To enhance elasticity</p> Signup and view all the answers

Which type of collagen is responsible for binding type II fibrils found in cartilage?

<p>Type IX</p> Signup and view all the answers

How is fibronectin structured?

<p>As usually heterodimers with multiple domains</p> Signup and view all the answers

What is a key chemical property of elastin?

<p>Hydrophobic protein</p> Signup and view all the answers

Study Notes

Cell Adhesion and Cell Signalling

  • Topics covered include adhesion in epithelia, the extracellular matrix, and cell-cell and cell-matrix adhesion
  • Learning objectives include describing ECM components, understanding how ECM contributes to tissue structure and function, discussing adhesion molecules, understanding their role in cellular function (especially the immune system), and the role of adhesion in tissues (especially epithelia). Understanding cellular signaling with examples of pathways and components.
  • Recommended textbook is Alberts et al. Molecular Biology of the Cell, Chapter 19.
  • Topics for Biochemistry and Cell Biology lectures include what is the extracellular matrix?, and how do cells adhere to each other and ECM

What Holds Us Together

  • Cells need to stick to each other and to other parts to form multicellular organisms.
  • Cells and components are organized into tissues.
  • Tissues are made of cells and extracellular space with a network of macromolecules forming the ECM
  • Cell adhesion mechanisms and the ECM are crucial for tissue organization, development, function, and dynamics.
  • The roles and contributions of different parts of the ECM varies in different tissue types.

Extremes of Animal Tissue Organisation

  • Epithelial tissues are sheets of tightly bound cells; cell-cell adhesions are linked to the cytoskeleton, with a thin layer of ECM.
  • Connective tissues are rich in components (e.g., collagen fibers), have few cells (e.g., fibroblasts, fat cells, immune cells), and prioritize cell-matrix adhesions

Fibroblasts in Rat Cornea

  • Image shows fibroblasts in rat cornea.

Connective Tissue

  • ECM in connective tissues determines the physical properties.
  • Connective tissue provides pathways for communication and supply of blood vessels, nerves, and lymphatics.

Types of Connective Tissue

  • Tendons: rope-like, high tensile strength (collagen fibrils).
  • Blood vessels: resilient, flexible (elastic fibers).
  • Cartilage: tensile strength and elastic properties (collagen and proteoglycan aggrecan).
  • Bone: rigid and incompressible (calcified collagen).
  • Vitreous content of the eye: transparent jelly (collagen fibers and hyaluronan).
  • Different tissues have variants, proportions, and arrangements of similar components.

Components of the Extracellular Matrix

  • Two main component types are glycosaminoglycan (GAG) polysaccharide chains, and fibrous proteins.
  • GAGs include heparin sulfate, hyaluronan, proteoglycans, decorin, serglycin, perlecan, syndecan.
  • Fibrous proteins include collagen, fibrillin, elastin, and laminin.
  • Adhesive glycoproteins like fibrinogen, fibronectin, osteopontin, tenascin, and vitronectin are also present.

ECM Macromolecules

  • Proteoglycans and GAGs are shown in an image, as are fibrous proteins, and glycoproteins.
  • Hyaluronan and type IV collagen and fibrillar collagen are specific examples of components.
  • Illustrations depict molecular structures, sizes, and relationships within the ECM.

GAGs

  • Unbranched polysaccharide chains are composed of repeating disaccharide units.
  • One sugar is an amino sugar (N-acetylglucosamine or N-acetylgalactosamine).
  • The second is typically a uronic acid.
  • GAGs are highly negatively charged (sulfate and carboxyl groups).
  • Four main groups: hyaluronan, chondroitin sulfate, dermatan sulfate, heparan sulfate, and keratan sulfate.

Hyaluronan

  • Extremely long chain length (up to 25,000 disaccharide units).
  • Non-sulphated.
  • Highly extended conformation.
  • Attracts water, creating a non-compressible space filler.

Proteoglycan Synthesis

  • Proteoglycans are synthesized in the ER and golgi and transported via the secretory pathway.
  • Linkers add glycosyl transferases in ER/golgi.
  • Post-translational modifications occur in the Golgi.

Examples of Proteoglycans

  • Examples of proteoglycans and their properties (approximate molecular weight of core protein, type of GAG chains, number of GAG chains, location, and functions) are provided in a table, including Aggrecan, Betaglycan, Decorin, Perlecan, Syndecan-1, and Dally (Drosophila).
  • Proteoglycans are a variable form of a single core protein with varying numbers of GAGS.

Aggrecan in Cartilage

  • Image illustrating the structure of aggrecan and cartilage.

Rat Cartilage

  • Image showing a section of rat cartilage. The structure and components are shown

Collagens

  • Major fibrous ECM component, making up 25% of mammal's body protein (especially skin and bone).
  • 42 human genes for collagen a-chains (form triple helix).
  • Different combinations are expressed in tissues (~30 different molecules).

Collagen Fibrils in Tadpole Skin

  • Image showing collagen fibrils in tadpole skin.

Some Collagens Form Fibrils

  • Image showing bundles of collagen fibrils in connective tissue of embryonic chick skin.

Collagen α-chains Form Trimers

  • Each chain folds into a helix with three amino acids per turn (glycine-X-Y, where X and Y are often proline and hydroxyproline).
  • Chains wrap around each other to form a tightly packed triple-helical rod.

Collagen Trimers Can Form Fibrils

  • Collagen trimers self-assemble into fibrils (1.5 nm diameter).
  • Covalent crosslinks form between lysines and hydroxylysines (making them very strong and resistant to stretch).
  • Collagen fibrils bundle into fibres.

Synthesis and Assembly of Collagen

  • Steps in collagen synthesis and assembly, including pro-α-chain synthesis, hydroxylation, glycosylation, self-assembly, procollagen triple helix formation, secretion, cleavage of propeptides, self-assembly into fibrils, and aggregation to form fibers are illustrated.

Fibril-associated Collagens

  • Non-helical domains interrupt triple helix to make the molecule more flexible.
  • Retain propeptides so they don't aggregate into fibrils.
  • Bind to fibrils to interact with other ECM molecules and determine fibril organization (e.g., type IX with II in cartilage, type XII with I in tendons).
  • Images are present.

Types of Collagen and Their Properties

  • Table summarizing properties (tissue distribution, polymerized form) of different collagen types, including fibril-forming and fibril-associated types. Mutant phenotypes associated with a given type of collagen (related to the structure or related disease) are also presented.

Elastic Fibres in Dog Aorta

  • Images (A and B) of elastic fibers in a dog aorta, showing different magnifications.

Elastin

  • Collagen fibrils provide tensile strength, but some tissues require elasticity (e.g., blood vessels, lungs, skin).
  • Elastic fibers provide resilience and the ability to recoil after stretch.
  • Elastin, a hydrophobic protein, is the primary component, secreted as tropoelastin and cross-linked to form a network of fibers and sheets.
  • Elastic fibers are often covered with microfibrils composed of other glycoproteins (e.g., fibrillin)

Fibronectin Helps Attach Cells to the ECM

  • Fibronectin forms dimers (usually heterodimers - a result of differential splicing).
  • Each subunit has multiple functionally distinct domains and repeated modules (e.g., type III fibronectin repeat).
  • Fibronectin can also form insoluble, crosslinked fibrils, but only when binding cells and subject to tension.

The Basal Lamina (Basement Membrane)

  • Thin, tough, flexible ECM sheet.
  • Essential for mechanical function (e.g., connecting epidermis to dermis).
  • Underlies epithelia and surrounds muscle and nerve cells

Examples of Basal Lamina

  • Examples of basal lamina in different tissue types (epithelial/luminal surface, muscle, kidney glomerulus).
  • Functions such as physical support, selective cell barrier, filtration, and acting as a template for tissue regeneration, cell polarity, cell metabolism influence, and cell proliferation and differentiation are noted.

Basal Lamina in Chick Embryo Cornea

  • Image showing basal lamina in chick embryo cornea.

Molecular Structure of Basal Lamina

  • Diagram illustrating the arrangement of components in the basal lamina. Key components like type IV collagen, perlecan, laminin, nidogen, and integrins are presented.

Laminin Structure

  • Laminin is a heterotrimer of α, β, and γ chains (multiple isoforms of each).
  • Laminin has multiple binding sites for other components and cells.
  • It assembles into a network via heads.

The Extracellular Matrix Is Secreted and Organized by Cells Within It

  • Fibroblasts, chondroblasts (cartilage), and osteoblasts (bone) secrete and assemble ECM components (e.g., collagen fibrils).
  • They bind ECM components via integrins and cytoskeleton (e.g., fibronectin fibrils).
  • Cells can orient the ECM.

Remodeling/Degradation of the ECM

  • Remodeling occurs during normal tissue development, wound healing, bone remodeling, cell migration (e.g., inflammation/wound healing), and tumour invasions;
  • Matrix metalloproteases (MMPs) degrade ECM (e.g., MMP-9-collagenase).
  • Serine proteases (e.g., urokinase-type plasminogen activator-uPA) are also involved, and are found in certain disease processes.)
  • MMP activity is localized and regulated by cell-surface localization/activation from inactive precursors and inhibitors.

Dendritic Cells Use MMPs to Degrade ECM

  • An image showing the action of dendritic cells using MMPs to degrade the ECM.

Roles of the ECM

  • Structural integrity of connective tissues.
  • Scaffold for cells.
  • Reservoir for growth factors and cytokines.
  • Pathways for cell migration.
  • Regulation of cell shape, polarity, survival, and proliferation.
  • Regulation of tissue development.

ECM Can Immobilize Chemokine Gradients

  • Image shows cells migrating into skin lymphatic vessels in response to chemokine gradients.

ECM Can Immobilize Chemokine Gradients (with Heparitinase)

  • Illustrative images of controlled cell migration and response to gradients.
  • A graph shows the effect of hepranitinase (which degrades ECM) versus a control group on dendritic cell migration into lymphatic vessels.

Extracellular Matrix Summary

  • Found in all tissues, playing a crucial structural role in connective tissues (resisting compressive forces and providing tensile strength).
  • Basal lamina provides cell organization scaffolding.
  • ECM comprises polysaccharides, fibrous proteins, and adhesive glycoproteins acting as adaptors.
  • Components are secreted and remodeled by cells.
  • Variations in their forms, amounts, and arrangement produce tissue-specific properties, and these properties greatly influence cell shape, polarity, and function and much more.

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Cell Adhesion and ECM PDF

Description

This quiz explores the critical roles of the extracellular matrix (ECM) and its components in connective tissues. It covers the structural integrity, cell organization, and various functions of the ECM, including its influence on cell behavior and tissue regeneration. Test your knowledge of ECM components and their significance in biological tissues.

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