Cell Adhesion and Signalling Quiz
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Questions and Answers

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

  • Type IX (correct)
  • Type I
  • Type XII
  • Type II

Elastic fibers in tissues are primarily composed of collagen.

False (B)

What is the main function of fibronectin in the extracellular matrix (ECM)?

Help attach cells to the ECM

The main component of elastic fibers is _____, which is secreted as tropoelastin.

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

Match the following components to their primary roles:

<p>Type IX collagen = Binds type II fibrils in cartilage Elastin = Provides resilience and recoil Fibronectin = Attaches cells to ECM Basal lamina = Provides a tough, flexible sheet of ECM</p> Signup and view all the answers

What is one function of the extracellular matrix (ECM)?

<p>To provide structural support to tissues (A)</p> Signup and view all the answers

Epithelial tissues have a thick layer of extracellular matrix (ECM).

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

What is the primary type of adhesion molecule that allows cells to adhere to each other?

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

The two extremes of animal tissue organization are _______ tissues and connective tissues.

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

Match the following types of tissues with their characteristics:

<p>Epithelial tissues = Sheets of tightly bound cells with minimal ECM Connective tissues = Rich in ECM components with few cells Cell-cell adhesion = Involves cadherins Cell-matrix adhesion = Involves integrins</p> Signup and view all the answers

Which component is primarily responsible for the tensile strength in the extracellular matrix?

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

Adhesion molecules are only important for the immune system.

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

Which type of connective tissue is known for its high tensile strength due to collagen fibrils?

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

Elastic fibers are mainly found in bone tissue.

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

What are the two main types of components in the extracellular matrix (ECM)?

<p>Glycosaminoglycan polysaccharide chains and fibrous proteins</p> Signup and view all the answers

The primary function of connective tissue is to provide _____ and communication routes.

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

Match the following connective tissues to their characteristics:

<p>Tendon = High tensile strength Cartilage = Tensile strength and elastic properties Bone = Rigid and incompressible Blood vessel walls = Resilient and flexible</p> Signup and view all the answers

Which of the following is a glycosaminoglycan found in the extracellular matrix?

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

Fibroblasts are responsible for producing the extracellular matrix in connective tissues.

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

Name one function of adhesive glycoproteins in the extracellular matrix.

<p>They bind matrix proteins, cells, or both.</p> Signup and view all the answers

In cartilage, the extracellular matrix contains collagen and _____ aggrecan.

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

Which of the following is NOT a group of Glycosaminoglycans (GAGs)?

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

Hyaluronan is a highly sulfated Glycosaminoglycan.

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

What type of sugar is always one of the repeating disaccharide units in GAGs?

<p>amino sugar</p> Signup and view all the answers

The four main groups of GAGs include hyaluronan, chondroitin sulfate, heparan sulfate, and __________ sulfate.

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

Match the following GAGs with their characteristics:

<p>Hyaluronan = Attracts water and creates pressure Chondroitin sulfate = Typically found in cartilage Heparan sulfate = Involved in cell signaling Keratan sulfate = Found in cornea and cartilage</p> Signup and view all the answers

Which of the following characteristics is true about GAGs?

<p>They contain repeating disaccharide units. (B)</p> Signup and view all the answers

Proteoglycan synthesis involves the translocation of an amino sugar.

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

What is the role of GAGs in the extracellular matrix?

<p>They provide structural support and create a hydrated environment.</p> Signup and view all the answers

GAGs have a __________ charge due to the presence of sulfate and carboxyl groups.

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

What is the maximum length of the hyaluronan chain?

<p>25,000 disaccharide units (B)</p> Signup and view all the answers

Which of the following statements about collagens is true?

<p>Collagens form the major fibrous extracellular matrix component. (D)</p> Signup and view all the answers

Proteoglycans can consist of up to 95% carbohydrate by weight.

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

What role do glycosyltransferases play in the cell?

<p>They are involved in the glycosylation process, adding carbohydrate chains to proteins.</p> Signup and view all the answers

Collagen trimers self-assemble into __________ in the extracellular matrix.

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

Match the following components with their respective characteristics:

<p>Glycosyltransferases = Enzymes that add carbohydrates to proteins Fibril-associated collagens = Do not form fibrils, have non-helical domains GAGs = Glycosaminoglycans that are part of proteoglycans Collagen fibers = Bundles of collagen fibrils</p> Signup and view all the answers

What is a common consequence of scurvy?

<p>Decreased collagen stability (A)</p> Signup and view all the answers

Collagen α-chains form without any twists or turns.

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

How many human genes are responsible for collagen α-chains?

<p>42</p> Signup and view all the answers

The __________ is a common GAG found in cartilage.

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

What type of carbohydrate molecule is primarily found in proteoglycans?

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

Flashcards

Extracellular Matrix (ECM)

A network of macromolecules that fills the space between cells in tissues.

Cell Adhesion

Mechanisms that allow cells to stick to each other and to the extracellular matrix (ECM).

Epithelial Tissues

Sheets of tightly bound cells with strong cell-cell adhesions and a thin layer of ECM.

Connective Tissues

Tissues rich in ECM components, containing few cells, and where cell-matrix adhesions are important.

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Cell-cell adhesion

Mechanisms that allow cells to stick to each other. Important for epithelial tissues.

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Cell-matrix adhesion

Mechanisms that allow cells to stick to the extracellular matrix. Important for connective tissues.

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Tissue Organization

Multicellular organisms organize cells and other components into tissues to maintain structure and function.

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GAGs

Unbranched polysaccharide chains composed of repeating disaccharide units. One sugar is always an amino sugar, the other usually a uronic acid. Highly negatively charged due to sulphate and carboxyl groups.

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Hyaluronan

An extremely long, non-sulphated GAG. It attracts water, creating pressure and non-compressible space. Acts as a filler in tissues.

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What makes GAGs negatively charged?

GAGs are negatively charged due to the presence of sulphate and carboxyl groups within their structure.

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What are the four main groups of GAGs?

The four main groups of GAGs are hyaluronan, chondroitin sulphate and dermatan sulphate, heparan sulphate, and keratan sulphate.

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What is the repeating disaccharide unit in heparan sulphate?

The repeating disaccharide unit in heparan sulphate is composed of glucosamine and glucuronic acid.

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What is the function of hyaluronan?

Hyaluronan attracts water, creating a pressure and non-compressible space. It acts as a filler in tissues, providing structure and cushioning.

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What is the difference between hyaluronan and other GAGs?

Hyaluronan is non-sulphated, while other GAGs are usually sulphated, making them more negatively charged and able to bind to proteins.

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How are proteoglycans synthesized?

Proteoglycans are synthesized by first translocating a core protein into the ER. A linker protein is then added, followed by the polysaccharide chain. Finally, modifications like sulphation occur.

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What is the function of GAGs in the ECM?

GAGs provide structure, support, and hydration to the ECM. They also interact with proteins, forming proteoglycans, which play important roles in cell signaling and adhesion.

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What is the relationship between GAGs and proteoglycans?

GAGs are the polysaccharide chains that attach to core proteins to form larger structures called proteoglycans. Proteoglycans are important components of the ECM, influencing its properties and interacting with cells.

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Collagen's Role

Collagen fibers provide tensile strength, resisting stretching. It's important for tissues like tendons and ligaments.

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Elastin's Function

Elastin fibers provide resilience, allowing tissues to stretch and recoil. This is crucial for blood vessels and lungs.

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Fibronectin's Job

Fibronectin acts as a bridge, attaching cells to the ECM. It helps form dimers and can create insoluble fibrils.

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Basal Lamina's Purpose

The basal lamina is a thin, strong sheet of ECM that provides mechanical support. It's vital for tissues like the skin and muscles.

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What are microfibrils made of?

Microfibrils are made of glycoproteins like fibrillin. They are found alongside elastic fibers, providing structural support.

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Proteoglycans

Large, complex molecules composed of a core protein with attached glycosaminoglycans (GAGs). They are major components of the extracellular matrix.

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Glycosaminoglycans (GAGs)

Long, unbranched polysaccharide chains made up of repeating disaccharide units. They are negatively charged and attract water, contributing to the gel-like properties of the ECM.

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Collagen

A fibrous protein that is the major component of the extracellular matrix. It provides structural support and tensile strength.

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Collagen Trimer

Three collagen α-chains that wind around one another, forming a triple helix.

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Collagen Fibrils

Bundles of collagen trimers that self-assemble into larger structures.

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Scurvy

A disease caused by a deficiency in vitamin C, which is needed for the proper synthesis of collagen.

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Fibril-associated collagens (FACITs)

Collagens that don't form fibrils due to non-helical domains interrupting their triple helix. They bind to fibrillar collagens and play a role in organizing the ECM.

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Glycosyltransferase

Enzymes that attach sugar molecules (glycans) to proteins or lipids. They play a crucial role in building complex carbohydrates in the ECM.

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Sulphation

The addition of sulfate groups to molecules. It's an important modification of GAGs, adding to their negative charge.

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Epimerisation

A reaction that converts a sugar molecule into a different isomer by changing the configuration of a specific carbon atom.

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ECM Composition

The extracellular matrix (ECM) consists of two main types of components: (1) Glycosaminoglycan polysaccharide chains (GAGs) such as heparin sulphate, hyaluronan, and (2) Fibrous proteins like collagen, elastin, fibrillin, and laminin.

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ECM Function in Tendon

In a tendon, the ECM is primarily composed of collagen fibrils. This arrangement gives tendons a rope-like structure, making them strong and resistant to pulling.

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ECM Function in Blood Vessels

The ECM in blood vessel walls is rich in elastic fibers. These fibers allow vessels to stretch and recoil, accommodating blood flow and pressure changes.

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ECM Function in Cartilage

Cartilage's ECM contains both collagen and proteoglycan aggrecan. This combination provides strength and flexibility, enabling cartilage to withstand pressure and movement.

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ECM Function in Bone

Bone's ECM is primarily made of calcified collagen, making it rigid and incompressible. This structure provides strong support and protection.

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ECM Function in Vitreous Humor

The 'jelly' of the eye, vitreous humor, is composed of collagen fibres and hyaluronan. This transparent gel helps maintain the eye's shape and provides support.

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ECM Adaptability

The ECM composition and arrangement can vary within different tissues to suit specific functional needs. This variation allows for a wide range of tissue properties and functions.

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Study Notes

Cell Adhesion and Cell Signalling

  • Topics covered include adhesion in epithelia, the extracellular matrix, and cell-cell and cell-matrix adhesion.

  • Specific learning objectives include describing the molecular components and functions of the extracellular matrix (ECM), understanding how the ECM contributes to tissue structure and function, and discussing various adhesion molecule families which allow cells to adhere to the ECM and each other.

  • Another learning objective includes understanding the roles of adhesion molecules in cellular functions and in epithelial tissues.

  • Students should understand the principles of cellular signalling and be able to discuss examples of signaling pathways and their components.

Extracellular Matrix (ECM)

  • The ECM is a network of macromolecules that fills the space between cells in tissues.

  • Key components include glycosaminoglycan (GAG) polysaccharide chains (e.g., heparin sulfate, hyaluronan), fibrous proteins (e.g., collagen, fibrillin, elastin, laminin), and adhesive glycoproteins (e.g., fibrinogen, fibronectin, osteopontin).

  • ECM determines the tissue's physical properties.

  • Different tissues have different ECM compositions allowing for varied function (eg. tensile strength, flexibility).

Components of the Extracellular Matrix (ECM)

  • GAGs: Unbranched polysaccharide chains with repeating disaccharide units, commonly containing amino sugars and uronic acids. They are negatively charged, and attract water, creating a non-compressible space filler. Examples include hyaluronan, chondroitin sulfate, dermatan sulfate, heparan sulfate, and keratan sulfate.

  • Fibrous proteins: Provide strength and support. Examples include collagen (major component in mammals, forms triple helices), fibrillin, elastin, and laminin.

  • Adhesive glycoproteins: Act as adapters, mediating interactions between the ECM, cells, and other matrix proteins. Examples include fibrinogen, fibronectin, osteopontin, tenascin, and vitronectin.

Types of Connective Tissue

  • Tendons: Rope-like, high tensile strength, primarily collagen fibrils.

  • Blood vessel walls: Resilient and flexible, containing elastic fibres.

  • Cartilage: Provides tensile strength and elasticity using collagen and proteoglycan aggrecan.

  • Bone: Rigid and incompressible featuring calcified collagen.

  • Vitreous humor of the eye: Transparent jelly with collagen fibres and hyaluronan.

Proteoglycans

  • Proteoglycans are a type of glycoprotein with a core protein covalently linked to GAGs.

  • Varying amount of proteoglycan will vary the characteristics of the connective tissue

Collagen Summary

  • Collagen is the major fibrous ECM component.

  • It constitutes about 25% of total mammalian protein mass, is prevalent in skin and bone.

  • Human genes encode different collagen α-chains, which form triple helices, and combine in various forms in different tissues.

  • Collagen α-chains fold into a helix and wrap around each other forming tightly packed triple-helical rods and trimers.

  • Collagen trimers form fibrils and fibrils frequently bundle into fibres giving tensile and structural support.

ECM Remodeling and Degradation

  • ECM remodeling and degradation occur during normal tissue development, wound healing, bone remodeling, cell migration (inflammation), and tumor invasion/metastasis.

  • These processes depend on cellular proteases, including matrix metalloproteinases (MMPs) and serine proteases (like uPA).

  • Cells control the activity of proteases by regulating their localizations.

  • Inhibitors such as TIMPs and serpins control protease activity.

Basal Lamina

  • The basal lamina is a thin, tough ECM sheet underlying epithelia and surrounding muscle and nerve cells.

  • It connects the epidermis to dermis.

  • It offers a foundation for cell organization, polarity, and influences cell metabolism.

  • It helps maintain cell survival, proliferation, and differentiation.

  • It is made of type IV collagen, laminin, perlecan, and nidogen.

Elastic Fibres

  • Elastic fibres provide tissues with resilience and recoil after stretch, essential in tissues such as blood vessels, lungs, and skin.

  • The primary component of elastic fibres is elastin - a hydrophobic protein which when secreted forms a cross-linked network of fibres.

  • The network of fibres is also covered with microfibrils, made of other glycoproteins such as fibrillin.

Fibronectin

  • Fibronectin is an adhesive glycoprotein that attaches cells to the ECM.

  • Fibronectin assembles into dimers or longer structures, often crosslinking with itself.

  • The molecule has various binding domains, including ones for cells, collagen, and heparin.

  • Fibronectin can bundle into fibrils especially when under tension.

ECM Functions

  • The ECM provides structural support, a scaffold for cells, and regulates cell shape, polarity, survival, proliferation and function.

  • It also acts as a reservoir for growth factors and cytokines, and provides pathways for cell migration and communication.

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Cell Adhesion and Cell Signalling PDF

Description

Test your knowledge on cell adhesion, the molecular components of the extracellular matrix, and the principles of cellular signalling. This quiz covers adhesion in epithelia and the roles of various adhesion molecules in tissue structure and cellular functions. Understand the mechanics behind how cells interact and communicate through these crucial processes.

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