Podcast
Questions and Answers
Cells are bound together via ______ complexes.
Cells are bound together via ______ complexes.
junctional
Epithelial sheets connect cells to form structures that line ______ and surfaces.
Epithelial sheets connect cells to form structures that line ______ and surfaces.
cavities
The apical surface is free and exposed to the air or to a watery ______.
The apical surface is free and exposed to the air or to a watery ______.
fluid
The basal surface of epithelial cells is attached to a sheet of connective tissue called the ______.
The basal surface of epithelial cells is attached to a sheet of connective tissue called the ______.
In many tissues, each cell is separated from the next by an extracellular ______.
In many tissues, each cell is separated from the next by an extracellular ______.
There are five different types of cell ______ found in epithelial cells.
There are five different types of cell ______ found in epithelial cells.
Tight junctions act as barriers between fluid ______.
Tight junctions act as barriers between fluid ______.
Tight junctions form seals that prevent the free passage of molecules between the cells of ______ sheets.
Tight junctions form seals that prevent the free passage of molecules between the cells of ______ sheets.
One function of tight junctions is to separate the apical and ______ domains of the plasma membrane.
One function of tight junctions is to separate the apical and ______ domains of the plasma membrane.
Occludin is a major component of the tight junction and is a ______ protein.
Occludin is a major component of the tight junction and is a ______ protein.
Tight junctions prevent the free diffusion of lipids and membrane ______ between the apical and basolateral domains.
Tight junctions prevent the free diffusion of lipids and membrane ______ between the apical and basolateral domains.
Tight junctions allow ______ transport and paracellular transport.
Tight junctions allow ______ transport and paracellular transport.
The tight junction protein Occludin has a short N-terminal and a much longer ______ region exposed in the cytosol.
The tight junction protein Occludin has a short N-terminal and a much longer ______ region exposed in the cytosol.
The binding to occludin on adjacent cells is known as ______ binding.
The binding to occludin on adjacent cells is known as ______ binding.
The first extracellular loop of claudin is hypothesized to determine paracellular tightness and selective ion ______.
The first extracellular loop of claudin is hypothesized to determine paracellular tightness and selective ion ______.
Junction Adhesion Molecules (JAM) are part of the immunoglobulin ______ family.
Junction Adhesion Molecules (JAM) are part of the immunoglobulin ______ family.
Tight junctions help to regulate the paracellular pathway function and maintain cell ______.
Tight junctions help to regulate the paracellular pathway function and maintain cell ______.
Tight junctions provide minimal adhesive strength compared to ______ junctions.
Tight junctions provide minimal adhesive strength compared to ______ junctions.
Cadherins, which are responsible for adherens junctions, require ______ to bind effectively.
Cadherins, which are responsible for adherens junctions, require ______ to bind effectively.
Tight junction dysfunction is characterized by a reduction of tight junction ______.
Tight junction dysfunction is characterized by a reduction of tight junction ______.
Anchoring junctions connect the cytoskeleton to a neighbor or to the ______.
Anchoring junctions connect the cytoskeleton to a neighbor or to the ______.
Linker proteins β-catenin and p120 bind to the cytosolic tails of cadherins binding it to ______.
Linker proteins β-catenin and p120 bind to the cytosolic tails of cadherins binding it to ______.
E-cadherin acts as a tumour ______.
E-cadherin acts as a tumour ______.
Desmosomes are similar to ______ junctions.
Desmosomes are similar to ______ junctions.
Desmosomes contain specialised nonclassical cadherins that link to ______ filaments instead of actin filaments.
Desmosomes contain specialised nonclassical cadherins that link to ______ filaments instead of actin filaments.
Pemphigus is a severe autoimmune blistering skin disease caused by autoantibodies primarily targeting the ______ required for firm adhesion.
Pemphigus is a severe autoimmune blistering skin disease caused by autoantibodies primarily targeting the ______ required for firm adhesion.
Hemidesmosomes anchor cells to the ______ lamina.
Hemidesmosomes anchor cells to the ______ lamina.
Integrins in hemidesmosomes attach to intermediate filaments and the protein ______ present in the basal lamina.
Integrins in hemidesmosomes attach to intermediate filaments and the protein ______ present in the basal lamina.
Gap junctions provide direct connections between the ______ of adjacent cells.
Gap junctions provide direct connections between the ______ of adjacent cells.
Gap junctions are constructed of four-pass transmembrane proteins called ______.
Gap junctions are constructed of four-pass transmembrane proteins called ______.
Each gap junction consists of many ______ pairs in parallel.
Each gap junction consists of many ______ pairs in parallel.
Gap junctions allow ions and small molecules to diffuse between ______ cells.
Gap junctions allow ions and small molecules to diffuse between ______ cells.
There are at least ______ different human connexin proteins.
There are at least ______ different human connexin proteins.
Tight junctions help polarize cells and prevent leakage of extracellular ______.
Tight junctions help polarize cells and prevent leakage of extracellular ______.
The main proteins found at adherens junctions are ______ molecules.
The main proteins found at adherens junctions are ______ molecules.
Gap junctions couple cells metabolically, allowing one cell to provide necessary ______ to neighboring cells.
Gap junctions couple cells metabolically, allowing one cell to provide necessary ______ to neighboring cells.
Smooth muscle cells communicate through ______ junctions.
Smooth muscle cells communicate through ______ junctions.
Epithelial cells connect to one another to form epithelial sheets that line ______ throughout the animal body.
Epithelial cells connect to one another to form epithelial sheets that line ______ throughout the animal body.
The apical surface of epithelial cells is exposed to the air or to a watery ______.
The apical surface of epithelial cells is exposed to the air or to a watery ______.
Connective tissue is composed of cells surrounded by an extensive ______ matrix.
Connective tissue is composed of cells surrounded by an extensive ______ matrix.
The basal surface of epithelial cells is attached to a sheet of connective tissue called the basal ______.
The basal surface of epithelial cells is attached to a sheet of connective tissue called the basal ______.
Tight junctions act as barriers between fluid compartments and help to determine the ______ of the plasma membrane.
Tight junctions act as barriers between fluid compartments and help to determine the ______ of the plasma membrane.
Homophilic binding refers to binding between ______ cells.
Homophilic binding refers to binding between ______ cells.
Claudin proteins are hypothesized to determine the paracellular tightness and selective ion ______.
Claudin proteins are hypothesized to determine the paracellular tightness and selective ion ______.
Tight junction dysfunction is observed in conditions such as ______ disease.
Tight junction dysfunction is observed in conditions such as ______ disease.
Cadherins are a family of proteins that require ______ to bind to one another.
Cadherins are a family of proteins that require ______ to bind to one another.
The intracellular tails of transmembrane proteins in tight junctions bind to cytosolic proteins in the zonula ______ family.
The intracellular tails of transmembrane proteins in tight junctions bind to cytosolic proteins in the zonula ______ family.
Desmosomes contain specialized nonclassical cadherins that link to ______ filaments.
Desmosomes contain specialized nonclassical cadherins that link to ______ filaments.
Transmembrane proteins called ______ are major components of tight junctions.
Transmembrane proteins called ______ are major components of tight junctions.
Tight junctions separate the ______ and basolateral domains of the plasma membrane.
Tight junctions separate the ______ and basolateral domains of the plasma membrane.
Tight junctions form seals that prevent the free passage of ______ between cells.
Tight junctions form seals that prevent the free passage of ______ between cells.
The main function of tight junctions is to act as barriers between fluid ______.
The main function of tight junctions is to act as barriers between fluid ______.
One type of junction that connects the cytoskeleton to neighboring cells is called a ______ junction.
One type of junction that connects the cytoskeleton to neighboring cells is called a ______ junction.
Hemidesmosomes anchor epithelial cells to the ______ lamina.
Hemidesmosomes anchor epithelial cells to the ______ lamina.
Cadherins, which are a key component of adherens junctions, require ______ to bind effectively.
Cadherins, which are a key component of adherens junctions, require ______ to bind effectively.
Gap junctions allow for direct communication between the ______ of adjacent cells.
Gap junctions allow for direct communication between the ______ of adjacent cells.
Desmosomes provide mechanical ______ to epithelia.
Desmosomes provide mechanical ______ to epithelia.
The loss of E-cadherin correlates with increased invasiveness and ______ of tumors.
The loss of E-cadherin correlates with increased invasiveness and ______ of tumors.
Desmosomes resist mechanical stress due to their strongly ______ state.
Desmosomes resist mechanical stress due to their strongly ______ state.
Gap junctions are formed from different combinations of ______, which create channels with varying properties.
Gap junctions are formed from different combinations of ______, which create channels with varying properties.
A connexon is a structure formed when ______ connexins assemble together.
A connexon is a structure formed when ______ connexins assemble together.
Gap junctions allow for the movement of ______ and small molecules between adjacent cells.
Gap junctions allow for the movement of ______ and small molecules between adjacent cells.
The main function of gap junctions is to couple cells ______ and electrically.
The main function of gap junctions is to couple cells ______ and electrically.
Gap junctions consist of connexon pairs that form a sort of ______ to facilitate communication.
Gap junctions consist of connexon pairs that form a sort of ______ to facilitate communication.
Cardiac and smooth muscle communicate primarily through ______ junctions.
Cardiac and smooth muscle communicate primarily through ______ junctions.
Different tissues can exhibit varying ______ and regulation in their gap junctions.
Different tissues can exhibit varying ______ and regulation in their gap junctions.
In heart muscle, gap junctions ensure that electrical signals are ______ to neighbouring cells.
In heart muscle, gap junctions ensure that electrical signals are ______ to neighbouring cells.
What is the primary purpose of tight junctions in epithelial cells?
What is the primary purpose of tight junctions in epithelial cells?
Which of the following proteins are crucial for the adhesion in adherens junctions?
Which of the following proteins are crucial for the adhesion in adherens junctions?
What distinguishes epithelial sheets from connective tissues in terms of cellular arrangement?
What distinguishes epithelial sheets from connective tissues in terms of cellular arrangement?
Which type of junction connects the cytoskeleton to neighboring cells, providing mechanical strength?
Which type of junction connects the cytoskeleton to neighboring cells, providing mechanical strength?
What role do gap junctions play in cellular communication?
What role do gap junctions play in cellular communication?
Which transmembrane protein is a major component of tight junctions?
Which transmembrane protein is a major component of tight junctions?
Which statement accurately describes the function of tight junctions?
Which statement accurately describes the function of tight junctions?
What characterizes the arrangement of proteins in tight junctions?
What characterizes the arrangement of proteins in tight junctions?
What is the significance of the C-terminal region of Occludin?
What is the significance of the C-terminal region of Occludin?
What is one method by which tight junctions manage transport across epithelial cells?
What is one method by which tight junctions manage transport across epithelial cells?
What type of junction is primarily involved in the adhesion process between epithelial cells?
What type of junction is primarily involved in the adhesion process between epithelial cells?
What happens to tight junctions during tight junction dysfunction?
What happens to tight junctions during tight junction dysfunction?
What structure is formed when six connexins assemble together?
What structure is formed when six connexins assemble together?
What type of molecules can diffuse through gap junctions?
What type of molecules can diffuse through gap junctions?
Which type of junction helps in sealing neighboring cells to prevent leakage of extracellular molecules?
Which type of junction helps in sealing neighboring cells to prevent leakage of extracellular molecules?
In which type of muscle cells are gap junctions notably important for communication?
In which type of muscle cells are gap junctions notably important for communication?
How do gap junctions influence metabolic activity between cells?
How do gap junctions influence metabolic activity between cells?
Which of the following proteins primarily forms gap junctions?
Which of the following proteins primarily forms gap junctions?
What is the primary function of adherens junctions?
What is the primary function of adherens junctions?
How does the permeability of gap junctions vary between different tissues?
How does the permeability of gap junctions vary between different tissues?
What is the role of E-cadherin in the context of cancer?
What is the role of E-cadherin in the context of cancer?
Which protein is primarily responsible for linking cadherins to the actin cytoskeleton?
Which protein is primarily responsible for linking cadherins to the actin cytoskeleton?
What do desmosomes primarily provide to epithelial tissues?
What do desmosomes primarily provide to epithelial tissues?
Which of the following statements about hemidesmosomes is accurate?
Which of the following statements about hemidesmosomes is accurate?
Pemphigus is a disease resulting from autoantibodies targeting which component?
Pemphigus is a disease resulting from autoantibodies targeting which component?
Which type of junction provides direct communication between the cytoplasm of adjacent cells?
Which type of junction provides direct communication between the cytoplasm of adjacent cells?
What is the function of integrins in hemidesmosomes?
What is the function of integrins in hemidesmosomes?
Which proteins are primarily involved in the adhesion of desmosomes?
Which proteins are primarily involved in the adhesion of desmosomes?
What type of binding occurs between occludin on adjacent cells within tight junctions?
What type of binding occurs between occludin on adjacent cells within tight junctions?
What is a hypothesized role of the first extracellular loop of claudin?
What is a hypothesized role of the first extracellular loop of claudin?
What is the primary function of Junction Adhesion Molecules (JAM)?
What is the primary function of Junction Adhesion Molecules (JAM)?
Which type of protein connects tight junctions to the actin cytoskeleton?
Which type of protein connects tight junctions to the actin cytoskeleton?
What directly contributes to tight junction dysfunction in Crohn's disease?
What directly contributes to tight junction dysfunction in Crohn's disease?
What role does calcium play in the function of cadherins within adherens junctions?
What role does calcium play in the function of cadherins within adherens junctions?
What distinguishes tight junctions from anchoring junctions in terms of strength?
What distinguishes tight junctions from anchoring junctions in terms of strength?
What is a key characteristic of desmosomes in relation to other junction types?
What is a key characteristic of desmosomes in relation to other junction types?
Which statement accurately describes the function of gap junctions in epithelial cells?
Which statement accurately describes the function of gap junctions in epithelial cells?
What is a key characteristic of hemidesmosomes in epithelial tissue?
What is a key characteristic of hemidesmosomes in epithelial tissue?
Which protein family is primarily involved in the formation of adherens junctions?
Which protein family is primarily involved in the formation of adherens junctions?
Which type of junction is characterized by its role in regulating paracellular transport?
Which type of junction is characterized by its role in regulating paracellular transport?
What role do claudin proteins play in tight junctions?
What role do claudin proteins play in tight junctions?
What is the primary structural unit of gap junctions?
What is the primary structural unit of gap junctions?
Which of the following best describes the function of gap junctions?
Which of the following best describes the function of gap junctions?
What is the primary role of the larger first extracellular loop of claudin in tight junctions?
What is the primary role of the larger first extracellular loop of claudin in tight junctions?
How many different human connexin proteins have been identified?
How many different human connexin proteins have been identified?
Which proteins link tight junctions to the actin cytoskeleton?
Which proteins link tight junctions to the actin cytoskeleton?
What is the significance of the differences in connexin composition in gap junctions across different tissues?
What is the significance of the differences in connexin composition in gap junctions across different tissues?
Which type of junction is primarily responsible for sealing cells together to prevent leakage in epithelial tissue?
Which type of junction is primarily responsible for sealing cells together to prevent leakage in epithelial tissue?
What is the molecular weight of Junction Adhesion Molecules (JAM)?
What is the molecular weight of Junction Adhesion Molecules (JAM)?
Which component of gap junctions allows ions and small molecules to diffuse between adjacent cells?
Which component of gap junctions allows ions and small molecules to diffuse between adjacent cells?
What characterizes the tight junction dysfunction observed in Crohn's disease?
What characterizes the tight junction dysfunction observed in Crohn's disease?
What role do connexins play in the formation of gap junctions?
What role do connexins play in the formation of gap junctions?
Why do cadherins require calcium in the extracellular medium?
Why do cadherins require calcium in the extracellular medium?
What type of binding occurs between occludin on adjacent cells?
What type of binding occurs between occludin on adjacent cells?
Which statement about the functionalities of gap junctions is correct?
Which statement about the functionalities of gap junctions is correct?
Which junction is primarily responsible for providing mechanical strength among epithelial cells?
Which junction is primarily responsible for providing mechanical strength among epithelial cells?
What is the effect of the shorter second extracellular loop of claudin on the paracellular cleft?
What is the effect of the shorter second extracellular loop of claudin on the paracellular cleft?
What role does β-catenin play in adherens junctions?
What role does β-catenin play in adherens junctions?
Which type of protein do desmosomes primarily use to connect to intermediate filaments?
Which type of protein do desmosomes primarily use to connect to intermediate filaments?
What is one of the primary functions of hemidesmosomes?
What is one of the primary functions of hemidesmosomes?
What disease is characterized by the autoantibodies targeting desmogleins?
What disease is characterized by the autoantibodies targeting desmogleins?
How does E-cadherin function in relation to tumors?
How does E-cadherin function in relation to tumors?
What is the function of gap junctions in cells?
What is the function of gap junctions in cells?
Which of the following best describes the structural difference between adherens junctions and desmosomes?
Which of the following best describes the structural difference between adherens junctions and desmosomes?
What component is found in hemidesmosomes that helps anchor cells to the basal lamina?
What component is found in hemidesmosomes that helps anchor cells to the basal lamina?
Which statement correctly describes the role of tight junctions in epithelial cells?
Which statement correctly describes the role of tight junctions in epithelial cells?
Which protein serves as a major component of tight junctions?
Which protein serves as a major component of tight junctions?
What type of transport do tight junctions primarily restrict?
What type of transport do tight junctions primarily restrict?
How do tight junctions contribute to the polarization of epithelial cells?
How do tight junctions contribute to the polarization of epithelial cells?
Which feature distinguishes tight junctions from other types of cell junctions?
Which feature distinguishes tight junctions from other types of cell junctions?
In what way does occludin differ from claudin in the context of tight junctions?
In what way does occludin differ from claudin in the context of tight junctions?
What is the primary function of the transmembrane proteins found in tight junctions?
What is the primary function of the transmembrane proteins found in tight junctions?
What type of connections do gap junctions provide between adjacent epithelial cells?
What type of connections do gap junctions provide between adjacent epithelial cells?
What is the primary function of tight junctions in epithelial cells?
What is the primary function of tight junctions in epithelial cells?
Which type of junction is primarily responsible for connecting cells to the extracellular matrix?
Which type of junction is primarily responsible for connecting cells to the extracellular matrix?
What type of proteins are involved in forming gap junctions?
What type of proteins are involved in forming gap junctions?
Which junction provides minimal adhesive strength compared to others?
Which junction provides minimal adhesive strength compared to others?
What is the role of cadherins in adherens junctions?
What is the role of cadherins in adherens junctions?
Which protein is a major component of tight junctions?
Which protein is a major component of tight junctions?
What do tight junctions help to separate in the plasma membrane?
What do tight junctions help to separate in the plasma membrane?
What type of transport do tight junctions primarily facilitate?
What type of transport do tight junctions primarily facilitate?
What characteristic structure do tight junctions form between epithelial cells?
What characteristic structure do tight junctions form between epithelial cells?
Which type of junction is primarily responsible for enabling strong adhesion between epithelial cells?
Which type of junction is primarily responsible for enabling strong adhesion between epithelial cells?
Which domain of the plasma membrane do tight junctions primarily interact with?
Which domain of the plasma membrane do tight junctions primarily interact with?
What is the weight of the Occludin protein typically associated with tight junctions?
What is the weight of the Occludin protein typically associated with tight junctions?
What role does E-cadherin play in the context of tumors?
What role does E-cadherin play in the context of tumors?
How do desmosomes contribute to epithelial tissue?
How do desmosomes contribute to epithelial tissue?
What type of junction anchors cells to the basal lamina?
What type of junction anchors cells to the basal lamina?
What do gap junctions primarily provide between adjacent cells?
What do gap junctions primarily provide between adjacent cells?
Which of the following proteins is found in desmosomes that link to intermediate filaments?
Which of the following proteins is found in desmosomes that link to intermediate filaments?
What is the function of β-catenin in adherens junctions?
What is the function of β-catenin in adherens junctions?
Which tissue structure is primarily linked by integrins in hemidesmosomes?
Which tissue structure is primarily linked by integrins in hemidesmosomes?
What structure is formed by six connexins in gap junctions?
What structure is formed by six connexins in gap junctions?
Which of the following allows for the direct transmission of electrical signals between adjacent cells?
Which of the following allows for the direct transmission of electrical signals between adjacent cells?
Which of the following is true regarding gap junctions?
Which of the following is true regarding gap junctions?
What is the main function of gap junctions in cardiac muscle cells?
What is the main function of gap junctions in cardiac muscle cells?
How do gap junctions couple cells metabolically?
How do gap junctions couple cells metabolically?
What type of proteins make up the pore structure in gap junctions?
What type of proteins make up the pore structure in gap junctions?
Which of these junctions is primarily responsible for sealing neighboring cells together to prevent leakage?
Which of these junctions is primarily responsible for sealing neighboring cells together to prevent leakage?
What is the role of claudin in tight junctions?
What is the role of claudin in tight junctions?
Which statement accurately describes Junction Adhesion Molecules (JAM)?
Which statement accurately describes Junction Adhesion Molecules (JAM)?
How do the intracellular tails of transmembrane proteins in tight junctions interact with the cytoskeleton?
How do the intracellular tails of transmembrane proteins in tight junctions interact with the cytoskeleton?
What distinguishes homophilic binding from heterophilic binding?
What distinguishes homophilic binding from heterophilic binding?
Which type of junction provides mechanical strength in epithelial tissues?
Which type of junction provides mechanical strength in epithelial tissues?
Which physiological condition is associated with tight junction dysfunction?
Which physiological condition is associated with tight junction dysfunction?
What is a requirement for cadherins to effectively bind to one another?
What is a requirement for cadherins to effectively bind to one another?
What is the primary feature of anchoring junctions?
What is the primary feature of anchoring junctions?
Flashcards
Cell junctions
Cell junctions
Specialized structures on cell membranes that allow cells to bind together, forming tissues.
Plasma Membrane
Plasma Membrane
The outermost layer of a cell, made of a phospholipid bilayer.
Basal lamina
Basal lamina
A thin, flexible sheet that lies beneath epithelial cells, providing support and separating them from connective tissue.
Apical surface
Apical surface
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Basolateral surface
Basolateral surface
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What are cell junctions?
What are cell junctions?
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What do tight junctions do?
What do tight junctions do?
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How do tight junctions contribute to cell polarity?
How do tight junctions contribute to cell polarity?
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What's the role of adherens junctions?
What's the role of adherens junctions?
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What do desmosomes do?
What do desmosomes do?
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What are hemidesmosomes?
What are hemidesmosomes?
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What are gap junctions?
What are gap junctions?
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What is occludin?
What is occludin?
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β-catenin and p120
β-catenin and p120
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Linker proteins
Linker proteins
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Gap junctions
Gap junctions
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Hemidesmosomes
Hemidesmosomes
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Desmosomes
Desmosomes
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Integrin
Integrin
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Pemphigus
Pemphigus
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Loss of E-cadherin
Loss of E-cadherin
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Connexon
Connexon
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Regulation of Gap Junctions
Regulation of Gap Junctions
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Electrical Coupling
Electrical Coupling
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Metabolic Coupling
Metabolic Coupling
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Smooth Muscle Cell Gap Junctions
Smooth Muscle Cell Gap Junctions
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Tight Junctions
Tight Junctions
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Occludin, Claudin, JAM
Occludin, Claudin, JAM
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What are tight junctions?
What are tight junctions?
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What is JAM-1?
What is JAM-1?
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What are tight junction cytoplasmic proteins?
What are tight junction cytoplasmic proteins?
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What is Crohn's disease?
What is Crohn's disease?
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What are anchoring junctions?
What are anchoring junctions?
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What are adherens junctions?
What are adherens junctions?
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Study Notes
Eukaryotic Cell Biology: Cell Contacts/Cell Junctions
- The lecture covers cell contacts/junctions in eukaryotic cells
- Students will understand that cells are bound together by junctional complexes
- Students will learn the different functions of these junctions
- Students will identify the proteins involved in the junctions
- Cells in many tissues, such as connective tissue, are separated by an extracellular matrix
- In some tissues (epithelia), adjacent cells' plasma membranes are pressed together
- This close contact enables the cells to function as an integrated unit
Levels of Cell Organization
- Cellular organization progresses from cells to tissues, organs, organ systems, and finally to an organism
- Cells form the building blocks for all advanced structures
- The progression from single cell to complex organism reflects the organization of cells into larger functional units.
Cells Like to Stick Together
- Cells in diverse tissues are either connected by an extracellular matrix or directly pressed together via their plasma membranes
- Connective tissue components are often surrounded by a matrix (helps the tissue have structural integrity)
- In epithelial cells, plasma membranes of adjacent cells form tight junctions that help tissues function as an integrated unit.
Types of Cell Junctions
- There are five main types of cell junctions in epithelial cells:
- Tight junctions
- Adherens junctions
- Desmosomes
- Hemidesmosomes
- Gap junctions
Tight Junctions
- Tight junctions act as barriers between fluid compartments
- They prevent molecules from passing between epithelial cells
- Tight junctions separate the apical and basolateral domains of the plasma membrane
- They regulate the passage of molecules across the epithelium
- They are formed by transmembrane proteins (e.g., occludin, claudin, JAM)
- Different tight junction proteins have different roles in regulating paracellular transport
Anchoring Junctions
- Anchoring junctions connect the cytoskeleton of one cell to another or to the extracellular matrix (ECM)
- They include adherens junctions and desmosomes
- Adherens junctions connect to actin filaments while desmosomes are attached to intermediate filaments
- They are vital for structural integrity and mechanical strength of tissues
Adherens Junctions
- The main proteins involved are cell adhesion molecules (cadherins)
- Cadherins bind to each other in the extracellular space, requiring calcium
- These junctions are tightly linked to the intracellular actin cytoskeleton
- A process called 'homophilic binding' strengthens the link
Desmosomes
- Desmosomes form specialized plaques composed of proteins inside the cell
- They link to intermediate filaments (e.g., keratin)
- The strong adhesion of desmosomes makes tissues more resistant to mechanical stress
- Certain skin and heart diseases can arise from desmosome defects
Hemidesmosomes
- Hemidesmosomes do not link cells to each other; instead, they anchor cells to the basal lamina (part of the ECM)
- Crucial proteins include transmembrane integrins that attach to intermediate filaments (e.g., keratin) and the ECM protein laminin
- They are important for structural integrity and resistance to mechanical stress
- They function in joining cells to an underlying basal lamina
Gap Junctions
- Gap junctions are channels that connect the cytoplasm of adjacent cells
- Made of connexin proteins which form connexons
- They allow ions and small molecules to pass between cells
- Gap junctions are important for cell-to-cell communication and coordination of activities between adjacent cells
- They control the flow of small molecules, allowing coordination and communication between cardiac cells and smooth muscle cells.
Tight Junction Dysfunction
- Tight junction dysfunction can lead to various health issues (e.g., Crohn's disease)
- Such dysfunction can lead to abnormal passage of undigested food particles, toxins and bacteria
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Description
This quiz covers the essential aspects of cell contacts and junctions in eukaryotic cells. Students will explore the types of junctional complexes and their functions, as well as the proteins involved in these connections. Understanding how cells organize into tissues and systems is crucial for comprehending their integrated function.
