Epithelial and Connective Tissues Overview

These flashcards cover the main distinctions between epithelial and connective tissues, their structures, components, and functional roles in biology.

What is a key characteristic of connective tissue?

The extracellular matrix is plentiful, with sparse cells.

What protein is a major component of the extracellular matrix?

Collagen.

What is collagen composed of in terms of structure?

Collagen is formed by three polypeptide chains that wrap around each other to form a triple helix.

Why is glycine important in collagen's structure?

Glycine is the smallest amino acid, allowing tight packing of collagen strands.

What role do cells play in organizing collagen fibers?

They crawl on matrix collagen, pulling and arranging the fibers into ordered tracks.

What is fibronectin?

A key protein that helps cells attach to the extracellular matrix.

What do integrins do?

Integrins integrate cellular surfaces with the extracellular environment.

How do integrins behave uniquely compared to other receptors?

They can be activated from both outside-in and inside-out.

What is the role of proteoglycans in the extracellular matrix?

They consist of protein-polysaccharide complexes that attract water and provide structure.

What are glycosaminoglycans?

Long polysaccharides that are part of proteoglycans, consisting of repeating glucose derivatives.

What is a characteristic feature of proteoglycans?

They are highly hydrophilic and can form large hydrated spaces.

How do extracellular matrices affect molecular diffusion?

They can mediate selective passage based on molecular size.

What is columnar epithelium?

Epithelium composed of tall, thin cells.

What is squamous epithelium?

Epithelium made up of flat, broad cells.

Define cell polarity in the context of epithelial cells.

Epithelial cells have distinct apical and basolateral surfaces.

What is the function of tight junctions?

They prevent the movement of molecules between the apical and basolateral sides of epithelial cells.

What proteins are involved in tight junctions?

Occludin and claudin.

How can the function of tight junctions be experimentally tested?

By applying a molecule on one side and checking if it penetrates to the other side.

What is the role of cadherins in anchoring junctions?

They form homotypic interactions and bind to either actin or intermediate filaments.

What is apical constriction?

A process where the top side of cells becomes smaller, aiding in tissue shape changes.

How does the process of gastrulation utilize apical constriction?

Cells invaginate to form new embryonic layers.

What type of junction is crucial for rapid electrical coupling between cells?

Gap junctions.

Where are gap junctions commonly found?

In heart tissue and between certain fast-communicating neurons.

What information about extracellular matrix should be kept in mind for exams?

Its components, roles in cell signaling, and structure.

How does the extracellular matrix contribute to cell migration?

It provides surfaces for cells to attach and move along.

What is the average protein mass percentage that collagen represents in a person?

About a quarter of a person's protein mass.

What is the stability of collagen's triple helix due to?

The arrangement of glycine residues at every third position.

Describe the hierarchical structure of proteoglycans.

They consist of a long core polysaccharide with proteins and side chain polysaccharides attached.

What happens if proteins are improperly localized in epithelial cells?

It can disrupt the function of transporters and lead to ineffective substrate transport.

What are the consequences of doing experiments with cadherins?

You can disaggregate cells or study cell-to-cell connections.

What does the term 'homotypic interaction' refer to in cadherins?

It's when cadherin proteins attach to the same type of cadherin on another cell.

What cellular structure does actin contribute to, related to cell shape?

It helps cells contract and change shape.

What is one method to study the action of tight junctions?

Using tracer molecules to see if they penetrate through the junction.

What do intermediate filaments connect to in epithelial tissues?

They are attached to cadherins, providing structural support.

In what process do cells constrict during embryonic development?

During gastrulation, causing invagination.

What type of protein mediates the attachment of cells to the extracellular matrix?

Integrins.

What is the main role of the extracellular matrix in relation to cells?

To provide structural support and facilitate cell signaling.

How do glycosaminoglycans affect the extracellular environment?

They attract water, creating hydrated spaces.

What do we mean by 'polarity' in epithelial cells?

Epithelial cells have different functional sides: apical and basolateral.

What are junctions that combine epithelial cells called?

Cell junctions, including tight and adherens junctions.

What are the components primarily found in connective tissues?

A matrix of proteins and polysaccharides.

What structure helps in rapid electrical signaling between heart cells?

Gap junctions.

What happens to extracellular matrix molecules when they are hydrated?

They swell and create spaces for cell movement and nutrient passage.

What adhesive function do integrins have regarding collagen?

They bind cells to collagen fibers in the extracellular matrix.

What is unique about the activation of integrins?

They can be activated from both the extracellular and intracellular sides.

Which junctions can prevent water and solute movement between epithelial cells?

Tight junctions.

What experimental techniques can demonstrate the function of cadherins?

Disaggregating cells and observing reaggregation based on cadherin types.