Retta - L21 part 2

Questions and Answers

What component of glycosaminoglycans (GAGs) is typically responsible for the attraction of cations such as sodium?

The presence of repeating disaccharide units

The linkage formed with the core protein

The sulphation of the amino sugars (correct)

The linear structure of the protein

In glycoproteins, how does the sugar portion differ from that in proteoglycans?

It contains repeating disaccharide units

It is more dominant in overall structure

It consists of longer unbranched chains

It forms short highly branched chains (correct)

Which statement about the structure of proteoglycans is true?

They can have 10 to 15 GAG chains attached to their core protein. (correct)

They consist solely of glycosaminoglycans.

They are stabilized primarily by hydrogen bonds.

They contain no covalent bonds between GAGs and proteins.

What is the function of glycosaminoglycans in tissues?

Allowing tissues to withstand compressive forces due to their hydration Signup and view all the answers

Which component is involved in linking GAGs to the core protein of proteoglycans?

Tetra-saccharide link Signup and view all the answers

What distinguishes proteoglycans from glycoproteins in terms of structure?

Proteoglycans often have multiple GAG chains attached to a core protein. Signup and view all the answers

Which statement about collagen types is incorrect?

Type 4 collagen is involved in fibril formation. Signup and view all the answers

What is the primary role of pro-collagen in the extracellular matrix (ECM)?

To undergo cleavage and maturation into functional collagen. Signup and view all the answers

How do cells influence the organization of collagen fibers in the ECM?

Through mechanical tension exerted on the matrix. Signup and view all the answers

How do proteoglycans interact with other proteins in the extracellular matrix?

They can modify the activity of other proteins such as proteases. Signup and view all the answers

What is the significance of elastin in the extracellular matrix?

To confer elasticity primarily to blood vessels and skin. Signup and view all the answers

What characterizes the collagen molecule structure?

It is a long, stiff, triple-stranded helix with three interacting alpha chains. Signup and view all the answers

What is a significant outcome of a mutation in the gene encoding type 1 collagen?

Severe bone defects and fractures, such as osteogenesis imperfecta. Signup and view all the answers

What protein is affected by mutations in the fibrillin gene, leading to Marfan syndrome?

Fibrillin. Signup and view all the answers

Which sequence is essential for the binding of integrins to fibronectin?

RGD sequence. Signup and view all the answers

What role do GAG chains play in the structure of proteoglycans?

They are numerous and can significantly alter the size of the proteoglycan. Signup and view all the answers

What is the main reason scientists study the interaction between integrins and fibrinogen?

To create anticoagulant drugs that interfere with clot formation. Signup and view all the answers

How do the cross-links in elastin fibers contribute to its function?

They allow the fibers to stretch and relax. Signup and view all the answers

What role does fibronectin play in the extracellular matrix?

It helps in the assembly and organization of ECM components. Signup and view all the answers

What is the major function of the basal lamina in relation to epithelial tissues?

It acts as a barrier for selective molecule passage. Signup and view all the answers

Which of the following correctly describes the composition of the basal lamina?

Laminin and type 4 collagen. Signup and view all the answers

What type of molecules do integrins bind to within the basal lamina?

Laminin and type 4 collagen. Signup and view all the answers

What role do matrix metalloproteinases (MMPs) play in extracellular matrix (ECM) dynamics?

They cleave ECM molecules for remodeling. Signup and view all the answers

How do cancer cells utilize matrix metalloproteinases?

To invade surrounding tissues by degrading ECM. Signup and view all the answers

Which of the following components of the basal lamina has varied tissue distributions due to its different isoforms?

Laminin. Signup and view all the answers

What is the primary purpose of the basal lamina in nerve and muscle regeneration?

To provide scaffolding for new tissue development. Signup and view all the answers

What do the various types of alpha, beta, and gamma chains in laminin contribute to?

Creation of diverse laminin isoforms. Signup and view all the answers

Which model organism is recognized for its utility in understanding developmental biology?

Nematode (Caenorhabditis elegans). Signup and view all the answers

During embryonic development, what does the process of differentiation allow?

Specialization of cells for different tissue types. Signup and view all the answers

What does it indicate if a transplanted cell retains the features of its original region in a different environment?

The cell is already determined. Signup and view all the answers

In the context of cell fate determination, how does differential gene expression contribute to cellular identity?

It facilitates the activation of certain genes for specific cell functions. Signup and view all the answers

What role do inductive signals play in the differentiation of cells?

They instruct neighboring undifferentiated cells to acquire specific fates. Signup and view all the answers

How does cell memory affect the response of cells to subsequent signals?

Cells respond differently based on their history of signals received. Signup and view all the answers

What is the significance of a gradient of soluble signals during cell differentiation?

It allows cells to sense and respond differently based on their proximity to the morphogen source. Signup and view all the answers

What is the primary role of beta 1 integrin during early embryonic development?

To enable the implantation of the embryo Signup and view all the answers

How does the process of specification differ from determination in cellular fate?

Specification can be altered by environmental factors while determination cannot Signup and view all the answers

What is the significance of E-cadherin in embryonic development?

Its mutation can lead to embryonic lethality at early stages Signup and view all the answers

What occurs during the compaction phase of embryonic development?

Cells at the 8-cell stage become tightly packed together Signup and view all the answers

Which of the following describes the role of cadherins during development?

They create cellular junctions that stabilize cell interactions Signup and view all the answers

At which stage of embryonic development does the blastocoel cavity form?

Blastocyst stage Signup and view all the answers

What is the main difference between differentiation and determination?

Differentiation involves visible changes while determination does not Signup and view all the answers

What happens to a specified cell when it is isolated from its environment?

It will still follow the fate it was instructed, but not visibly Signup and view all the answers

What defines the morula stage in embryonic development?

Solid ball of cells prior to blastocyst formation Signup and view all the answers

During embryonic development, which factor directly influences cell fate decisions?

Induction events and the surrounding environment Signup and view all the answers

What is the role of procollagen in collagen maturation?

It is cleaved to remove pro-peptides, facilitating the formation of mature collagen. Signup and view all the answers

How do cells exert influence over the organization of collagen in the extracellular matrix (ECM)?

Through mechanical tension exerted on collagen fibers to guide their alignment. Signup and view all the answers

What is one consequence of mutations in the fibrillin gene?

Developing aortic rupture and connective tissue disorders such as Marfan syndrome. Signup and view all the answers

What characterizes the structure of glycosaminoglycans (GAGs)?

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

Why is the RGD sequence significant in the context of fibronectin and integrin binding?

It serves as a recognition site for integrins, facilitating cell adhesion. Signup and view all the answers

How do glycosaminoglycans (GAGs) contribute to tissue functions?

By attracting cations that draw water into the matrix. Signup and view all the answers

What is the primary function of the disulfide bonds in fibronectin?

To link fibronectin repeats, providing structural integrity. Signup and view all the answers

In what way does the sugar portion of proteoglycans differ from that of glycoproteins?

Proteoglycans have longer and unbranched sugar chains. Signup and view all the answers

Which aspects contribute to the dominance of GAGs in the structure of proteoglycans?

Their repeated disaccharide composition. Signup and view all the answers

What is the primary structural component that links glycosaminoglycans to protein in proteoglycans?

Tetra-saccharide link. Signup and view all the answers

Which protein is the principal component of skin and bones, associated with severe bone defects when mutated?

Collagen type 1 Signup and view all the answers

Which proteoglycan is known for being transmembrane and has GAG chains attached to it?

Syndecan Signup and view all the answers

What is the main function of glycosaminoglycans in the extracellular matrix?

Regulating the activity of secreted proteins Signup and view all the answers

Which type of collagen is primarily present in cartilage and is linked to dwarfism when deficient?

Collagen type 2 Signup and view all the answers

What characterizes the structure of a typical collagen molecule?

Three alpha chains forming a triple stranded helix Signup and view all the answers

Which component of the basal lamina is specifically responsible for forming a cross-like structure?

Laminin Signup and view all the answers

What is the major function of matrix metalloproteinases (MMPs) in the extracellular matrix?

They cleave extracellular matrix molecules and allow remodeling. Signup and view all the answers

How do laminin receptors function in relation to the basal lamina?

They interact with integrins and bind to the basal lamina components. Signup and view all the answers

In what way are the alpha, beta, and gamma chains of laminin significant?

They provide varied tissue distributions and binding capabilities. Signup and view all the answers

During the process of embryonic development, what role does differentiation play?

It enables cells to become specialized for forming specific tissues. Signup and view all the answers

Study Notes

Glycosaminoglycan (GAG) Chains

Proteoglycans consist of glycosaminoglycan (GAG) chains covalently linked to core proteins.
GAGs are built from repetitive disaccharides, including an amino sugar (N-acetylglucosamine or N-acetylgalactosamine) and a uronic acid (glucuronic or iduronic acid).
GAGs attract cations like sodium, creating highly hydrated gels that help tissues endure compressive stress.
Major roles of GAGs include involvement in wound healing and constituting joint fluid.
Three of four GAG types are covalently attached to proteins, forming proteoglycans which dominate the structure of these macromolecules.

Structural Differences: Glycoproteins vs. Proteoglycans

Glycoproteins have shorter, branched sugar chains, while proteoglycans feature long and unbranched sugar chains with repeating disaccharides.
Sugar components in proteoglycans often make up the bulk of the molecule, with examples like Aggrecan containing over 100 GAG chains.
Decorin is a smaller proteoglycan with 1 to 10 GAG chains and is involved in decorating collagen fibrils.

Proteoglycans and ECM Regulation

Extracellular matrix (ECM) regulates secreted protein activities; some proteins can be sequestered within the ECM and activated based on signaling needs.
Proteoglycans can modulate the function of proteases and inhibitors, allowing for controlled signaling through their actions.
Certain proteoglycans, such as Syndecan, serve as transmembrane proteins that interact with the ECM and can be cleaved by proteases.

Collagen in the ECM

Collagen is a principal protein within the ECM and exhibits a distinctive triple-stranded helical structure.
Over 25 distinct collagen alpha chains exist, encoded by separate genes, leading to at least 20 types of collagen in connective tissues.
Major types include Type 1 (skin, bone), Type 2 (cartilage, intervertebral discs), and Type 4 (basal lamina), each with unique roles and deficiencies linked to specific diseases.

Fibroblast Function and Collagen Organization

Collagen fibers are organized through cell-mediated tension and can adopt various orientations, influencing tissue structure and function.
Fibril-associated collagen, like Type 9, contributes to cross-linking between collagen fibrils, enhancing structural integrity.

Elastin and Tissue Elasticity

Elastin provides elasticity to tissues, especially in arteries (like the aorta), skin, and lungs, allowing them to recoil after stretching.
Mutations in elastin-related genes can lead to conditions such as Marfan syndrome, affecting connective tissue health.

Roles of Glycoproteins in ECM

Fibronectin, a key glycoprotein, forms dimers and has multiple binding sites for integrins, crucial for cell adhesion and signaling.
RGD sequences in fibronectin and fibrinogen facilitate integrin binding, leading to signal transduction essential for cellular responses.
Disintegrins from snake venom inhibit blood clotting by interfering with these integrin interactions.

ECM Remodeling and Matrix Metalloproteinases

Matrix metalloproteinases (MMPs) are enzymes that cleave ECM components, essential for tissue remodeling and regeneration.
MMP activity is pivotal in cancer progression, enabling tumors to invade surrounding tissues by breaking down the ECM framework.

Development and Stem Cells

The fertilized egg's genome drives the differentiation of cells into specialized tissues as development progresses through stages like gastrulation.
Pattern information and cell differentiation are fundamental to forming diverse tissue types and their respective functions in multicellular organisms.### Model Organisms in Developmental Biology
Nematode (Caenorhabditis elegans): Valuable in developmental studies due to its simplicity and well-mapped genome.
Fruit fly (Drosophila melanogaster): Widely used for genetic studies and understanding biological processes.
Sea urchins (Echinodermata): Serve as models for studying fertilization and early development.
African clawed frog (Xenopus laevis): Important for embryonic development studies, particularly due to its large eggs.
Chick (Gallus gallus): Malpighi's early 17th-century drawings provide a historical framework for developmental stages.
Mouse (Mus musculus): Commonly used in mammalian genetics and developmental biology.
Plant (Arabidopsis thaliana): Model organism in plant biology for genetics and developmental studies.

Early Mammalian Development

Cells harbor identical genetic material, yet specialize through processes known as cell fate determination and differentiation.
Specialization results in cells with specific functions and characteristics based on their position and interactions.
Beta 1 integrin is crucial for early developmental stages, particularly for implantation.

Embryonic Development Stages

Cleavage Processes: Mammals exhibit rotational cleavage, while echinoderms and amphibians undergo radial cleavage.
Compaction: Occurs at the 8-cell stage, leading to the formation of the morula, which eventually develops into the blastocyst.
Cell Interactions: Essential for the expression of different proteins which direct cell specialization.

Cadherins and E-cadherins

Cadherins facilitate cell-cell junction formation; E-cadherin is critical for proper embryonic development.
Mutations in E-cadherin can lead to embryonic lethality, emphasizing its importance in differentiation.

Cell Fate Specification and Determination

Specification: Cells can change fate based on environmental cues; specifies what a cell will become without permanent commitment.
Determination: Cells reach a point where fate becomes fixed and cannot change regardless of environmental conditions.
Changes in gene expression lead cells to differentiate into specific types observable at the phenotypic level.

Inductive Interactions

Cells secrete factors influencing nearby cells; findings illustrate the significance of direct contact and soluble signals in development.
Differing developmental cues can activate distinct signaling pathways, ultimately guiding fate determination.

Stem Cells and Their Capabilities

Stem Cells: Capable of self-renewal; give rise to differentiated cells via asymmetric division.
Types of Stem Cells:
- Totipotent: Can generate all cell types.
- Pluripotent: Limited to specific lineages (e.g., ectoderm, mesoderm).
- Multipotent: Restricted to a smaller subset of cell types.

Stem Cell Plasticity and Applications

Embryonic stem cells are derived from the inner cell mass of blastocysts and are pluripotent.
Induced pluripotent stem cells (iPS cells) can be created from somatic cells using transcription factors, allowing for patient-specific therapeutic applications.
iPS cells facilitate research into disease mechanisms, drug testing, and potential gene therapies.

Ethical Considerations

Ethical issues arise with embryonic stem cells due to the destruction of embryos; adult and induced stem cells bypass these concerns.
The creation of transgenic animals through embryonic stem cells has advanced our understanding of genetics and medicine.

Application of Stem Cells

iPS cells can be used to develop models of diseases and test new therapeutic compounds.
Gene therapy approaches may allow for correction of genetic defects by manipulating patient-derived cells before reintegration into the patient.