Cell Biology: Cellular Adhesion and Organization

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Questions and Answers

What is the primary function of microvilli in cells?

To synthesize proteins for cellular function

To provide structural support for the cell

To regulate the flow of materials into the cell

To increase the surface area for absorption (correct)

Which of the following statements accurately describes the relationship between microvilli and absorptive capacity?

The presence of microvilli is inversely proportional to the cell's absorptive capacity.

Cells with tall, closely packed microvilli have a higher absorptive capacity than cells with short, irregular microvilli. (correct)

Cells with short, irregular microvilli have a higher absorptive capacity than cells with tall, closely packed microvilli.

The number and shape of microvilli do not influence a cell's absorptive capacity.

What is the structural basis for the motile nature of cilia and flagella?

Microtubules (correct)

Actin filaments

Collagen fibers

Intermediate filaments

Which of the following cell junctions is responsible for preventing the flow of materials between cells?

Tight junctions Signup and view all the answers

Which of the following proteins is primarily involved in the formation of tight junctions?

Occludins Signup and view all the answers

Which of the following cell junctions is responsible for providing strong adhesion between cells?

Desmosomes Signup and view all the answers

Which of the following cell junctions allows for communication between adjacent cells?

Gap junctions Signup and view all the answers

What is the correct order of cell junctions from the apical to the basal ends of a cell?

Tight junctions à adhering junctions à desmosomes à gap junctions à hemidesmosomes Signup and view all the answers

What is the primary function of tight junctions in epithelial tissues?

To prevent the flow of materials between cells. Signup and view all the answers

Which type of cell junction is primarily responsible for cell-to-cell communication?

Gap junctions Signup and view all the answers

Which of the following is NOT a function of anchoring junctions?

To regulate the passage of materials between cells. Signup and view all the answers

What is the primary protein involved in the formation of anchoring junctions?

Cadherin Signup and view all the answers

Which type of cell junction is involved in the attachment of epithelial cells to the basal lamina?

Hemidesmosomes Signup and view all the answers

What is the role of the nuclear pore complexes in the context of cell junctions?

They are involved in the organization and regulation of chromatin within the nucleus. Signup and view all the answers

What is the main difference between desmosomes and hemidesmosomes?

Desmosomes are made of cadherins, while hemidesmosomes are made of integrins. Signup and view all the answers

Which of the following statements accurately describes the arrangement of cell junctions from apical to basal ends of epithelial cells?

Tight junctions -> Adhering junctions -> Desmosomes -> Gap junctions -> Hemidesmosomes Signup and view all the answers

What function does the cell membrane primarily serve regarding ion concentration?

Regulates passage of materials. Signup and view all the answers

Which of the following correctly describes phagocytosis?

Entails the engulfment of large particles. Signup and view all the answers

Which type of endocytosis involves the detachment of receptors from the membrane?

Receptor mediated endocytosis. Signup and view all the answers

What is the main outcome of exocytosis?

Release of contents into the extracellular space. Signup and view all the answers

The fluid mosaic model describes the cell membrane as having a structure characterized by what two main components?

Fluidity of lipid bilayer and mosaic of membrane proteins. Signup and view all the answers

What are microvilli primarily associated with in the apical domain?

Absorption and increasing surface area. Signup and view all the answers

Which process is specifically characterized as 'cell drinking'?

Pinocytosis. Signup and view all the answers

What role do receptors play in the receptor mediated endocytosis process?

They bind to specific substances for absorption. Signup and view all the answers

Study Notes

Chromatin and Nuclear Structure

Participates in chromatin organization and anchors nuclear pore complexes.

Cell Junctions Overview

Composed of multiprotein complexes facilitating contact between neighboring cells or with the extracellular matrix.
Critical for intercellular adhesion and communication, especially prominent in epithelial tissues.

Intercellular Adhesion Functions

Tight (occluding) junctions prevent material flow between cells; formed by occludin proteins.
Anchoring junctions (adhering junctions) provide adhesion and do not hinder material passage; rely on cadherin proteins.
Gap junctions facilitate communication between adjacent cells, constructed from connexin proteins.
Junction types arranged from apical to basal: Tight junctions → Adhering junctions → Desmosomes → Gap junctions → Hemidesmosomes.

Types of Anchoring Junctions

Desmosomes: Points of attachment between cells, anchored to intermediate filaments.
Hemidesmosomes: Bind epithelial cells to the basal lamina, containing integrins instead of cadherins.

Cell Membrane Characteristics

Exhibits a fluid mosaic appearance due to the lipid bilayer and embedded proteins.

Cell Membrane Functions

Acts as a selective barrier regulating ion concentration and maintaining intracellular environment.
Performs specific recognition and regulatory functions.
Facilitates cell interactions, including adhesion and signaling.

Endocytosis Mechanisms

Phagocytosis ("cell eating"): WBCs like macrophages engulf and digest materials (e.g., bacteria).
Pinocytosis ("cell drinking"): Small particles are taken into the cell, forming vesicles that break down within lysosomes.
Receptor-mediated endocytosis: Cells absorb specific substances via inward budding of vesicles with receptor proteins.

Exocytosis Process

Vesicles fuse with the plasma membrane to release contents into the extracellular space without compromising membrane integrity.

Cell Surface Specialization

Apical Domain

Microvilli: Projections increasing surface area, crucial for absorption. Height and shape relate to absorptive capacity.
Stereocilia: Long immotile microvilli found in the epididymis and inner ear, aiding absorption.
Cilia and Flagella: Motile structures with a microtubule core (9+2 pattern), cilia primarily sweep fluids across cell surfaces.

Lateral Domain

Tight junctions maintain barriers to fluid flow.
Adhering junctions strengthen cell layers and stabilizing junctions beneath tight junctions.
Organizes junctions from the apical to basal ends: Tight junctions → Adhering junctions → Desmosomes → Gap junctions → Hemidesmosomes.

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Description

Learn about the structures and mechanisms that facilitate cell adhesion and communication, including chromatin organization and nuclear pore complexes.