Extracellular Matrix and Collagen Overview

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Questions and Answers

What primarily influences cellular behavior through cell-surface receptors?

Cytoskeleton

Extracellular matrix (correct)

Endoplasmic reticulum

Nuclear envelope

What structural feature do collagen molecules have?

Hexamer of six chains

Single polypeptide chain

Trimer of three chains (correct)

Dimer of two chains

How does the arrangement of collagen molecules in a fibril enhance its properties?

By increasing flexibility

By incorporating elastin fibers

By providing a staggered arrangement (correct)

By forming a solid mass

What happens to mammary gland epithelial cells when the surrounding ECM is digested?

Cells shrink and lose differentiated state Signup and view all the answers

What is a primary function of the basement membrane?

Acts as a barrier to macromolecules Signup and view all the answers

What is the result of continued cross-linking of collagen fibrils in the elderly?

Reduced skin elasticity Signup and view all the answers

In which tissue is the ECM most prominently found?

Connective tissue Signup and view all the answers

How are collagen fibers in tendons arranged to optimize their function?

Aligned parallel to the tendon’s long axis Signup and view all the answers

What structure allows Type IV collagen trimer to provide flexibility in basement membranes?

Nonhelical segments Signup and view all the answers

How do glycosaminoglycans (GAGs) contribute to the mechanical properties of tissues?

By attracting cations and forming hydrated gels Signup and view all the answers

What is the primary function of proteoglycan aggregates in connective tissues?

Providing resistance to compression Signup and view all the answers

Which of the following best describes the role of integrins in cells?

They facilitate attachment to the ECM and influence signaling. Signup and view all the answers

What is the likely result when cells from different developing organs are mixed?

They self-sort into homogeneous clusters. Signup and view all the answers

Where are desmosomes predominantly found?

In tissues subject to mechanical stress Signup and view all the answers

What is the characteristic feature of the junctional complex?

It contains tight junctions, gap junctions, and desmosomes. Signup and view all the answers

What type of enzyme is involved in the degradation of the extracellular matrix?

Matrix metalloproteinases (MMPs) Signup and view all the answers

What is the term for the continual, unregulated synthesis and secretion of substances from the cell?

Constitutive secretion Signup and view all the answers

Which of the following substances are synthesized in the Golgi apparatus?

Lipids and carbohydrates Signup and view all the answers

During a pulse-chase experiment, what is the role of the pulse step?

To introduce labeled amino acids Signup and view all the answers

What excatly is the chase step in a pulse-chase experiment?

Transfer to a medium with unlabeled amino acids Signup and view all the answers

How are proteins targeted to their specific destinations within the cell?

Using sorting signals recognized by receptors Signup and view all the answers

What technique allows visualization of specific proteins in a living cell?

Using green fluorescent protein (GFP) Signup and view all the answers

What general term describes the breaking apart of the cytomembrane system into smaller components?

Homogenization Signup and view all the answers

Where does radiolabeling first appear in the cell when tissues are incubated with radioactive amino acids?

In the rough endoplasmic reticulum (RER) Signup and view all the answers

What physiological changes occur in cells due to ligand binding?

Alterations in cytoplasmic pH and Ca²⁺ concentration Signup and view all the answers

What is a primary characteristic of gap junctions?

They allow the synchronization of cellular responses by direct communication. Signup and view all the answers

How do connexons contribute to gap junction formation?

They align from adjacent cells to create intercellular channels. Signup and view all the answers

Why can’t plants exhibit specialized junctions like those in animal cells?

Cell adhesion molecules are absent and the presence of rigid cell walls limits direct contact. Signup and view all the answers

What is the function of pectin in industrial applications?

Provides a gel-like consistency in products like jams and jellies. Signup and view all the answers

What essential structural feature is shared between mature plant cell walls and corneal stroma?

Fibrous elements organized into perpendicular layers for strength. Signup and view all the answers

What defines the structure of plasmodesmata in plant cells?

Cylindrical channels lined by plasma membrane containing a desmotubule. Signup and view all the answers

How do viruses utilize plasmodesmata to move between plant cells?

They use movement proteins to widen plasmodesmata for larger particles. Signup and view all the answers

Which process primarily influences lipid composition changes as membranes progress through various compartments within the cell?

Selective inclusion during vesicle budding Signup and view all the answers

What is the role of glycosyltransferases in the Golgi complex?

They determine the sequence of sugar addition to glycoproteins. Signup and view all the answers

What initiates the unfolded protein response (UPR) in the endoplasmic reticulum?

Accumulation of misfolded proteins Signup and view all the answers

In the context of glycoprotein synthesis, what is the main function of GT when it interacts with a misfolded protein?

To add a glucose residue for further folding Signup and view all the answers

What model describes the transformation of Golgi cisternae as they progress from the cis to trans face?

The cisternal maturation model Signup and view all the answers

What type of transport occurs when vesicles move from the trans end back to the cis end of the Golgi complex?

Retrograde transport Signup and view all the answers

How can researchers observe the pathway of secretory proteins from the ER to the Golgi complex?

By employing fluorescently tagged proteins like GFP Signup and view all the answers

What is the primary function of protein coats on budding vesicles?

To assist in vesicle formation and cargo selection Signup and view all the answers

What causes the differences in lipid and protein composition of vesicles from different parts of the Golgi complex?

Their destination and function Signup and view all the answers

What is the observable effect in a yeast cell with a gene mutation that inhibits vesicle formation at the ER membrane?

Expanded ER cisternae Signup and view all the answers

What role does the enzyme oligosaccharyltransferase play in the RER?

It transfers sugar chains to proteins Signup and view all the answers

Which statement describes the function of molecular chaperones like BiP and calnexin?

They facilitate correct protein folding and prevent aggregation Signup and view all the answers

How can one demonstrate that the rough ER (RER) and smooth ER (SER) membranes are interconnected?

By tracking the diffusion of labeled lipids or proteins Signup and view all the answers

Which of the following processes occurs in the rough endoplasmic reticulum (RER)?

Protein synthesis Signup and view all the answers

What happens to the number of unfused vesicles in a yeast cell with a mutation affecting vesicle fusion?

They increase in number Signup and view all the answers

Which characteristic is true about the asymmetry of phospholipid bilayers?

Specific lipids are preferentially localized to one side Signup and view all the answers

Study Notes

Extracellular Matrix (ECM)

The ECM is a network of extracellular materials surrounding cells, regulating cell shape, adhesion, migration, growth, and differentiation.
It's composed of proteins like collagen and proteoglycans.
Interactions influence cellular behavior, regulating activities like migration, growth, and differentiation via cell-surface receptors.
Mammary gland epithelial cells lose differentiated state and secretory activities when treated with enzymes digesting the surrounding ECM.
ECM is prominent in connective tissues like cartilage, bones, tendons, and cornea.
Basement membrane functions include mechanical support, signalling, facilitating cell migration, tissue separation, and providing a barrier to cancer cells and macromolecules.

Collagen

Collagen is the most abundant protein in the human body, comprising over 25% of total protein.
Collagen molecules are composed of three polypeptide chains forming a triple helix.
Some collagen molecules assemble into fibrils, then into fibers.
Staggered arrangement of collagen molecules in fibrils creates strength and characteristic banding via covalent cross-links between lysine and hydroxylysine.
Cross-linking in elderly reduces skin elasticity, and increases bone brittleness.
Collagen fibers in tendons are aligned parallel to the tendon's long axis for optimal resistance to pulling forces.
Corneal stroma collagen layers are arranged orthogonally, for strength and transparency to reduce light scattering.

Other ECM components

Glycosaminoglycans (GAGs) are acidic polysaccharides with negative charges that attract cations and water, forming hydrated gels resisting compression.
Proteoglycans bind large amounts of water due to GAGs, contributing to the mechanical strength of tissues.
Laminin supports cell migration, growth, and differentiation

Endomembrane Systems

Electron micrographs show membrane-bound vesicles, channels, networks, and stacks of cisternae in the cell interior.
Vesicle trafficking pathways exist: biosynthetic (ER to Golgi to destinations) and endocytic (cell surface to compartments).
Golgi apparatus produces lipids, carbohydrates, and certain glycoproteins.
Constitutive secretion is continuous, unregulated substance release.
Endocytic pathway enables movement of substances into the cell.
Proteins are targeted to specific locations via signals.

Protein Sorting

Proteins have sorting signals (sequences or attached oligosaccharides) recognized by receptors.
This facilitates sorting into specific locations.
Radiolabeled amino acids initially appear in the rough ER, where proteins are synthesized.
Pulse-chase experiments track protein transport.
Vesicular transport and cisternal maturation models explain Golgi function.
Retrograde transport moves vesicles through the Golgi complex from trans to cis.
Protein coats (e.g., clathrin, COPI, COPII) facilitate vesicle formation and cargo selection.

Other Information

Molecular chaperones assist protein folding and prevent aggregation.
Membranes are derived from pre-existing membranes (not created de novo).
Asymmetrical phospholipid bilayers are established during membrane synthesis and maintained.
Glycoproteins (sugars) aid folding, binding, and protection from degradation.
Unfolded protein response (UPR) increases chaperone production and reduces protein synthesis when misfolded proteins accumulate.
Sensors in the ER monitor unfolded/misfolded protein concentration through direct binding or stress monitoring.

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Description

This quiz covers key concepts related to the Extracellular Matrix (ECM) and collagen, including their composition, functions, and roles in cellular behavior and connective tissues. Explore how ECM influences cell activities and the significance of collagen in the human body.