Extracellular Matrix in Animal Tissues

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Questions and Answers

What primary role does the extracellular matrix perform for cells?

It stores genetic information for the cells.

It detoxifies harmful substances in the body.

It regulates cell behavior and influences various functions. (correct)

It acts solely as a passive structural support.

Which of the following cells are primarily responsible for secreting matrix macromolecules in connective tissues?

Fibroblasts (correct)

Chondrocytes

Adipocytes

Osteocytes

What structural feature does the extracellular matrix NOT possess?

It can form a jelly-like substance like in jellyfish.

It can naturally undertake a rigid structure like in plants. (correct)

It can have a specialized organization such as in tendons.

It can be calcified to form bones.

Which type of cell is specifically responsible for forming bone?

Osteoblast Signup and view all the answers

What is a significant outcome of the orientation of the cytoskeleton in cells that produce the extracellular matrix?

It affects the orientation of the extracellular matrix itself. Signup and view all the answers

Which of the following best describes the composition of the extracellular matrix?

It is made up of a complex of macromolecules including proteins and polysaccharides. Signup and view all the answers

Which type of specialized extracellular matrix is found beneath all epithelial cells?

Basal lamina Signup and view all the answers

What characteristic of the extracellular matrix contributes to the tensile strength of tendons?

The rope-like organization of its components. Signup and view all the answers

What are the three major classes of macromolecules that construct the extracellular matrix?

Glycosaminoglycans, Fibrous proteins, Noncollagen glycoproteins Signup and view all the answers

Which of the following best describes the role of glycosaminoglycans (GAGs) in connective tissue?

They form hydrated gels that resist compressive forces. Signup and view all the answers

What is the typical structure of glycosaminoglycan (GAG) chains?

Unbranched polysaccharide chains consisting of repeating disaccharide units. Signup and view all the answers

What is the most anionic biological molecule known?

Heparin Signup and view all the answers

What structural component of the extracellular matrix primarily resists stretching forces?

Collagen fibrils Signup and view all the answers

Which of the following groups of GAGs includes heparin?

Heparin and heparan sulfate Signup and view all the answers

How do GAGs affect water retention in the extracellular matrix?

They attract cations that cause water to be osmotically active. Signup and view all the answers

Which macromolecule predominantly forms the gel-like ground substance in connective tissue?

Proteoglycans Signup and view all the answers

What happens to the extracellular matrix when there is a deficiency in GAG production?

It becomes overly rigid and less resilient. Signup and view all the answers

What primarily contributes to the unique blend of matrix components in each tissue?

Individual matrix-associated proteins and enzymes modifying behaviors. Signup and view all the answers

What roles do matrix glycoproteins serve in tissue?

They promote cell migration and settling. Signup and view all the answers

Which statement accurately describes hyaluronan?

It consists of a regular repeating sequence of disaccharide units. Signup and view all the answers

What allows the cartilage matrix to withstand high compressive pressures?

The characteristic swelling pressure from GAGs. Signup and view all the answers

What is the purpose of freeze substitution in tissue preparation?

To prevent the collapse of GAG chains. Signup and view all the answers

Which type of collagen is most common and primarily found in skin and bone?

Type I Signup and view all the answers

What characterizes the helical structure of collagen molecules?

It has a left-handed helical configuration. Signup and view all the answers

What role do syndecans play in fibroblasts?

They modulate integrin function. Signup and view all the answers

How many distinct genes code for different collagen α chains in humans?

42 Signup and view all the answers

Which of the following is true about GAG chains in proteoglycans?

They are faintly stained in electron micrographs. Signup and view all the answers

What is the main structural feature of the triple-stranded collagen molecule?

It has a rope-like superhelix structure. Signup and view all the answers

Collagen types IV and VII have specific roles; what defines their function?

They link collagen fibrils and are involved in attachment. Signup and view all the answers

Which protein is primarily linked to the actin cytoskeleton in syndecans?

Core protein Signup and view all the answers

What characteristic largely determines the assembly of collagen molecules?

The combination of expressed collagen α chain genes. Signup and view all the answers

Which types of collagens are known as fibril-associated collagens?

Type IX and XII Signup and view all the answers

Which amino acid is frequently found in collagen and helps maintain its helical structure?

Glycine Signup and view all the answers

What is one function of the proteoglycans in the extracellular matrix?

Influencing cell growth and proliferation. Signup and view all the answers

What distinguishes hyaluronan from typical glycosaminoglycans (GAGs)?

It does not contain sulfated sugars. Signup and view all the answers

Which process describes how hyaluronan is synthesized?

It is directly synthesized and spun out from the cell surface. Signup and view all the answers

What role does hyaluronan play during embryonic development?

It helps in creating a cell-free space for cell migration. Signup and view all the answers

What is a primary characteristic of proteoglycans?

They contain GAG chains covalently linked to a core protein. Signup and view all the answers

Which enzyme is responsible for degrading excess hyaluronan?

Hyaluronidase Signup and view all the answers

Which statement about the structure of GAG chains in proteoglycans is true?

They contain a repeating disaccharide unit. Signup and view all the answers

What is a significant feature of the GAG known as aggrecan?

It is a major component of cartilage with high molecular mass. Signup and view all the answers

What modification occurs to GAG chains in the Golgi apparatus?

Sulfation, increasing their negative charge. Signup and view all the answers

What role do proteoglycans have in the extracellular matrix?

They create large polymeric complexes with GAGs. Signup and view all the answers

What is a key distinction between proteoglycans and glycoproteins?

Proteoglycans can contain up to 95% carbohydrate by mass. Signup and view all the answers

How do decorin and aggrecan differ in terms of GAG chains?

Aggrecan has more than 100 GAG chains, while decorin has one. Signup and view all the answers

Which type of GAG is chondroitin sulfate composed of?

D-glucuronic acid and N-acetyl-D-galactosamine Signup and view all the answers

What is the main function of hyaluronan in joint fluid?

To reduce friction as a lubricant. Signup and view all the answers

What characterizes the molecular mass of large aggrecan aggregates?

In the range of 3 × 10⁶ daltons or more. Signup and view all the answers

What is the primary function of elastin in the extracellular matrix of arteries?

To provide elasticity and allow stretching and recoiling Signup and view all the answers

What effect do mutations in the elastin gene have on arteries?

Narrowing of the aorta and excessive smooth muscle cell proliferation Signup and view all the answers

Which protein is essential for the integrity of elastic fibers?

Fibrillin Signup and view all the answers

How do fibroblasts influence the extracellular matrix?

By synthesizing collagen and organizing it through mechanical interaction Signup and view all the answers

What is one consequence of an abnormally high density of the extracellular matrix?

Association with fibrotic diseases and potential cancer risk Signup and view all the answers

What role do microfibrils play in the extracellular matrix?

They serve as a scaffold for elastin deposition and can also be elastic Signup and view all the answers

What is the relationship between fibroblasts and collagen in the extracellular matrix?

Fibroblasts produce and orient collagen fibrils they synthesize Signup and view all the answers

What disease can result from mutations in the fibrillin gene?

Marfan syndrome Signup and view all the answers

What impact does the composition of the extracellular matrix have on stem cells?

It regulates their proliferation, migration, and developmental fate Signup and view all the answers

Which glycoproteins in the extracellular matrix help organize tissues?

Multidomain glycoproteins Signup and view all the answers

What is one role of fibronectin in the extracellular matrix?

To help organize the matrix and facilitate cell attachment Signup and view all the answers

Which collagen type is responsible for severe bone defects and fractures?

Type I Signup and view all the answers

What structural feature is associated with collagen fibrils during their formation?

They require a specific orientation contributed by fibroblasts Signup and view all the answers

What is the primary function of propeptides in procollagen?

They guide the intracellular formation of triple-stranded collagen molecules. Signup and view all the answers

How does the behavior of fibroblasts change as the extracellular matrix density varies?

Fibroblasts migrate more freely in low-density matrices Signup and view all the answers

What happens to collagen production in scurvy due to vitamin C deficiency?

Collagen production is inhibited due to unstable pro-α chains. Signup and view all the answers

Which property is unique to collagen and elastin regarding covalent bonds?

Certain lysines and hydroxylysines are deaminated to form reactive aldehyde groups. Signup and view all the answers

Which collagen types are each composed of two or three types of α chains?

Types I, V, and XI Signup and view all the answers

What is a primary consequence of inhibited cross-linking in collagen?

Fragile collagenous tissues that tear easily. Signup and view all the answers

In which tissue type is Type II collagen predominantly found?

Cartilage Signup and view all the answers

What effect does glycosylation of hydroxylysines have on collagen?

It enhances the stability of the triple helical structure. Signup and view all the answers

What states a characteristic of Type IV collagen?

Creates a sheet-like network. Signup and view all the answers

What is the role of the enzyme lysyl oxidase in collagen formation?

It deaminates lysines and hydroxylysines to form aldehyde groups. Signup and view all the answers

What pattern do collagen fibrils in mammalian skin follow to resist tensile stress?

Wickerwork pattern Signup and view all the answers

What can result from the degradation of collagen in tissues?

Fragility in blood vessels and poor healing. Signup and view all the answers

How do connective-tissue cells influence the organization of collagen fibrils?

By secreting different types of matrix macromolecules Signup and view all the answers

What is a common feature of collagen types V and XI?

They are associated with type I and type II fibrils, respectively. Signup and view all the answers

What is a notable feature of fibril-associated collagens compared to fibrillar collagens?

They do not aggregate to form fibrils. Signup and view all the answers

Which type of collagen molecule is known to bind to type II collagen-containing fibrils?

Type IX collagen Signup and view all the answers

Which factor is essential for the hydroxylation of proline during collagen synthesis?

Ascorbic acid (vitamin C) Signup and view all the answers

What characterizes Type III collagen's tissue distribution?

Primarily in skin, blood vessels, and internal organs. Signup and view all the answers

What are elastic fibers primarily composed of?

Elastin and collagen Signup and view all the answers

What property enables tissues with elastic fibers to return to their original shape after being stretched?

Elastic properties of elastin Signup and view all the answers

What role does fibronectin play in collagen fibril formation?

It guides the organization of collagen fibrils. Signup and view all the answers

What characteristic of elastin contributes significantly to its rubberlike properties?

Random-coil conformation of polymer chains Signup and view all the answers

In what way does the arrangement of collagen fibrils in tendons differ from that in skin?

They are arranged in parallel bundles. Signup and view all the answers

What distinguishes fibril-associated collagens from fibrillar collagens in terms of structural characteristics?

They have interruptions in their helical structure. Signup and view all the answers

What primarily restricts the degree of stretching in tissues with elastic fibers?

The inelastic nature of collagen fibrils Signup and view all the answers

What activity happens to soluble tropoelastin once it is secreted into the extracellular space?

It assembles into elastic fibers. Signup and view all the answers

What factor is crucial for the assembly and characteristics of elastin fibers?

The specific types of amino acids present Signup and view all the answers

How are the different types of fibrillar collagen molecules expressed in connective-tissue cells?

By expressing one or more genes Signup and view all the answers

What is the approximate length of the type III fibronectin repeat?

90 amino acids Signup and view all the answers

What key function does the RGD sequence serve in fibronectin?

Binding to integrins Signup and view all the answers

How many times does the type III fibronectin repeat occur in each subunit of fibronectin?

What is the structural arrangement of the fibronectin dimer?

Linked at C-termini Signup and view all the answers

What type of proteins have sequences resembling epidermal growth factor (EGF) in their structure?

Matrix proteins Signup and view all the answers

Which of the following repeats are included in fibronectin?

Type I, II, and III Signup and view all the answers

What is the estimated total length of each fibronectin chain?

2500 amino acids Signup and view all the answers

Which of the following statements about fibronectin in mutant mice is true?

They die early in embryogenesis Signup and view all the answers

What role does alternative splicing play in the generation of fibronectin isoforms?

It produces multiple fibronectin isoforms Signup and view all the answers

In addition to fibronectin, which other types of proteins may contain an RGD sequence?

Other extracellular matrix proteins Signup and view all the answers

What is the function of the flexible polypeptide chains in fibronectin?

Enhance binding sites accessibility Signup and view all the answers

Which tripeptide sequence is necessary for cellular attachment to fibronectin?

Arg-Gly-Asp Signup and view all the answers

Fibronectin's structural diversity is increased by what process?

Exon splicing Signup and view all the answers

Which of the following best describes the binding domains of fibronectin?

Specialized for binding to specific molecules Signup and view all the answers

What is a distinctive feature of hyaluronan compared to other glycosaminoglycans?

It has a regular repeating sequence of identical disaccharide units. Signup and view all the answers

Which type of collagen is primarily associated with cartilage tissue?

Type II collagen Signup and view all the answers

What role does fibronectin play in the extracellular matrix?

It facilitates adhesion and migration of cells. Signup and view all the answers

What distinguishes fibrillar collagen from other types of collagen?

It assembles into long, rope-like structures. Signup and view all the answers

What role do integrins play in the assembly of fibronectin fibrils?

They link fibronectin molecules to the cell membrane and the actin cytoskeleton. Signup and view all the answers

Which of the following best describes the structure of the basal lamina?

It consists of a flexible network of type IV collagen. Signup and view all the answers

What is the primary function of the RGD sequence in extracellular proteins?

It serves as a binding site for integrins. Signup and view all the answers

Which characteristic is essential for fibronectin to assemble into fibrils?

Sufficient mechanical tension exerted on the fibronectin molecules. Signup and view all the answers

The primary structural characteristic of elastic fibers is due to which protein?

Elastin Signup and view all the answers

What is one primary function of the basal lamina?

To provide a dynamic scaffold that supports cell organization and survival. Signup and view all the answers

What type of collagen is predominantly found in the basal lamina?

Type IV collagen Signup and view all the answers

Which type of protease is specifically characterized by having a reactive serine in its active site?

Serine protease Signup and view all the answers

Which extracellular matrix components contribute to the specialized structure of the basal lamina?

Laminin, type IV collagen, nidogen, and perlecan. Signup and view all the answers

What is the role of matrix metalloproteinases in the extracellular matrix?

They degrade matrix proteins. Signup and view all the answers

How does tension on fibronectin affect its structural properties?

It causes fibronectin to unfold and exposes additional binding sites. Signup and view all the answers

Which feature is shared by all glycosaminoglycans (GAGs)?

They are composed of repeating disaccharide units. Signup and view all the answers

What is the typical thickness of the basal lamina?

40-120 nm Signup and view all the answers

What anatomical structures are often associated with the basal lamina?

Epithelial cells and Schwann cells Signup and view all the answers

What effect does fibronectin fibril assembly have on cell behavior?

It promotes cellular migration and communication. Signup and view all the answers

In what locations does the basal lamina play a critical role?

Underneath epithelial cells and surrounding certain muscle cells. Signup and view all the answers

What is a consequence of fibronectin being unable to assemble into fibrils in solution?

Cellular tension and surface interactions are necessary for its organization. Signup and view all the answers

What additional extracellular matrix component is mentioned as influential in the behavior of other molecules?

Type III fibronectin repeats Signup and view all the answers

What is one of the supportive roles of the basal lamina as highlighted in the content?

It organizes proteins in adjacent plasma membranes. Signup and view all the answers

What is the primary role of laminin in the basal lamina?

Organizing the sheet structure Signup and view all the answers

Which of the following statements about laminin is true?

Laminin heterotrimers can self-assemble into a network. Signup and view all the answers

What consequence occurs in mice that lack the laminin γ1 chain?

They are unable to form a basal lamina. Signup and view all the answers

Type IV collagen differs from fibrillar collagens primarily in its structure due to:

Interruptions that allow bending. Signup and view all the answers

Which cellular receptors play a crucial role in organizing basal lamina assembly?

Integrins and dystroglycan Signup and view all the answers

The basal lamina acts as a selective barrier primarily to prevent contact between:

Epithelial cells and fibroblasts Signup and view all the answers

Junctional epidermolysis bullosa is caused by:

Genetic defects in laminin-332 Signup and view all the answers

What role does the basal lamina play in tissue regeneration?

Acts as a scaffold for regenerating cells Signup and view all the answers

Which of the following best describes the composition of laminins?

Three polypeptide chains held by disulfide bonds Signup and view all the answers

Type IV collagen assembles into which kind of network in the basal lamina?

Flexible and felt-like Signup and view all the answers

Which isoform of laminin is specifically associated with muscle tissue?

Laminin-211 Signup and view all the answers

Which of these statements about the basal lamina is false?

It allows all types of cells to pass through freely. Signup and view all the answers

What is the relationship between laminin and integrins concerning the basal lamina?

Integrins facilitate the adhesion of laminin to cells. Signup and view all the answers

What is the primary role of heparan sulfate chains in proteoglycans?

They interact with secreted signal molecules. Signup and view all the answers

How do proteoglycans enhance the activity of fibroblast growth factors (FGFs)?

By oligomerizing FGF molecules and aiding receptor interaction. Signup and view all the answers

What is a crucial role of the basal lamina in relation to epithelial cells?

It provides mechanical support and regulates cell attachment. Signup and view all the answers

Which extracellular matrix component is primarily responsible for its tensile strength?

Fibrillar collagen Signup and view all the answers

What is the effect of a mutation in the gene encoding Dally in Drosophila?

Decreased activity of the signaling protein Dpp. Signup and view all the answers

What is a key feature of glycosaminoglycan (GAG) chains?

They attract water due to their negative charges. Signup and view all the answers

In what way do matrix glycoproteins influence cell behavior?

By directly activating cell-surface receptors. Signup and view all the answers

Which matrix molecule is involved in forming morphogen gradients during tissue development?

Proteoglycans Signup and view all the answers

What is a function of type IV collagen within the extracellular matrix?

It forms a sheet-like mesh structure in the basal lamina. Signup and view all the answers

What is a common function of matrix proteoglycans in cellular signaling?

Creating local reservoirs of signaling molecules. Signup and view all the answers

What characteristic differentials glypicans from other types of proteoglycans?

They are membrane-associated and linked to heparan sulfate. Signup and view all the answers

What effect do extensive arrays of binding domains in matrix glycoproteins have on signaling?

They influence the presentation of signal proteins to target cells. Signup and view all the answers

What role does the basal lamina play at the neuromuscular junction after an injury?

It directs regenerating nerve and muscle cells to the correct location. Signup and view all the answers

Which component of the basal lamina is responsible for regulating the assembly of acetylcholine receptors in muscle cells?

Agrin Signup and view all the answers

Why is the ability to degrade the extracellular matrix important for cells?

It enables division and migration through the matrix. Signup and view all the answers

What is the primary function of proteases in relation to the extracellular matrix?

To degrade matrix proteins. Signup and view all the answers

What are matrix metalloproteases primarily dependent on for their activity?

Calcium and zinc ions Signup and view all the answers

What happens to the structural integrity of the extracellular matrix due to the action of specific metalloproteases?

It is preserved while allowing for cell movement. Signup and view all the answers

What is a consequence of defects in components of the basal lamina?

Some forms of muscular dystrophy. Signup and view all the answers

How does localized degradation of matrix components affect white blood cells?

It allows them to escape from blood vessels into tissues. Signup and view all the answers

What is the largest group of matrix-degrading proteases in vertebrates?

Matrix metalloproteases Signup and view all the answers

What is a critical function of the proteolytic cleavage of type IV collagen?

It releases fragments that inhibit local blood vessel formation. Signup and view all the answers

Which type of protease is characterized by having a reactive serine in its active site?

Serine proteases Signup and view all the answers

What enables cells to divide while embedded in the extracellular matrix?

The production of extracellular proteolytic enzymes. Signup and view all the answers

Why is tight regulation of protease activity necessary?

To prevent uncontrolled matrix degradation and structural collapse. Signup and view all the answers

Study Notes

Extracellular Matrix of Animals

Tissues are composed of cells and an extracellular matrix (ECM) made of macromolecules.
ECM macromolecules are secreted by cells and assembled into a meshwork.
Variations in ECM composition and organization create diverse tissue properties, like bone (hard), cornea (transparent), and tendons (strong).
ECM is not just a passive support structure, it actively influences cell behavior (survival, development, migration, etc.).

Major ECM Macromolecules

ECM is composed of three major macromolecule types:
- Glycosaminoglycans (GAGs): Large, highly charged polysaccharides, usually covalently linked to protein as proteoglycans. They form hydrated gels that resist compression.
- Fibrous Proteins: Primarily collagens, forming strong structures.
- Noncollagen Glycoproteins: Diverse group, often multidomain, that mediate cell interactions and matrix organization.

GAG Chains

GAGs are unbranched polysaccharide chains of repeating disaccharide units.
They're highly negatively charged due to sulfate and carboxyl groups.
They occupy large volumes due to extended conformations.
These hydrated gels resist compression and enable rapid diffusion.
Hyaluronan is a simple, nonsulfated GAG that acts as a space filler during development and wound healing.
Proteoglycans, which contain GAG chains, have large carbohydrate components.

Proteoglycans

Most GAGs are part of proteoglycans.
Proteoglycans form a highly hydrated gel, embedding collagen and glycoproteins.
Collagens organize the matrix, elastin gives resilience.
Glycoproteins aid cell migration and differentiation.
Aggrecan, a large proteoglycan, forms aggregates with hyaluronan in cartilage.

Collagens

Collagens are a family of fibrous proteins, extremely abundant (e.g. 25% of total mammalian protein).
They have a unique triple-stranded helical structure.
Over 40 collagen types exist, with different tissues expressing different types.
Fibrillar collagens (like type I) aggregate into fibrils, providing tensile strength.
Fibril-associated collagens (like IX and XII) organize the fibrils.
Network-forming collagens (like IV) create specialized structures like basal lamina.
Collagen synthesis involves post-translational modifications (e.g. hydroxylation, glycosylation).
Propeptides help guide collagen formation and prevent premature fibril formation.
Extracellular enzymes remove propeptides to form collagen.
Covalent cross-links strengthen collagen fibrils.

Elastin

Elastin provides elasticity to tissues, like skin, blood vessels, and lungs.
It's a hydrophobic protein, rich in proline and glycine.
Elastin molecules cross-link into networks, giving the tissue resilience.
Elastin is surrounded by a microfibrillar sheath.
Microfibrils provide scaffold for elastin deposition.

Fibronectin

Fibronectin is a large multidomain glycoprotein.
It's involved in cell-matrix adhesion and cell migration.
Its RGD sequence binds to integrins on cell surfaces.
Fibronectin assembles into fibrils where tension is applied.

Basal Lamina

Basal lamina is a thin sheet of ECM separating cells from connective tissue.
It's composed mainly of laminin, type IV collagen, nidogen, perlecan.
It's crucial for epithelial attachment and cell organization.
Its diverse functions include cell polarity, migration, and cell signaling.

ECM Degradation

Cells degrade ECM via proteases (metalloproteases and serine proteases).
This allows cell division and movement.
Degradation is regulated for tissue structure.
Proteases can also generate active protein fragments.

ECM Regulation of Cell Signaling

Heparan sulfate chains of proteoglycans interact with signaling molecules (e.g., growth factors).
The ECM influences signal molecule diffusion and activity.
Matrix molecules can work as co-receptors.

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Description

Explore the crucial role of the extracellular matrix (ECM) in animal tissues. This quiz delves into the composition, major macromolecules, and the impact of ECM on cell behavior and tissue properties. Test your understanding of GAGs, fibrous proteins, and noncollagen glycoproteins.