48 Questions
Which protein forms hemidesmosomes and focal adhesions?
Integrins
What regulates gap junctions?
Cytosolic pH and free Ca2+ concentration
Which protein family includes L-selectin, E-selectin, and P-selectin?
Selectins
What can mutations in connexin genes cause?
Deafness, cataract, and heart malformations
What do hemidesmosomes anchor to the basal lamina?
Intermediate filaments
What are the major physiological roles of selectins?
Mediating lymphocyte binding to endothelium
What is the function of gap junction permeability?
Regulating the coordination of function in tissues
What do focal adhesions bind cells to?
Actin filaments
Which proteins mediate cell-cell adhesion and transient adhesions in the bloodstream?
Selectins
What is the role of anchoring junctions?
Binding cells to the extracellular matrix
What are the ligands of selectins?
Sialyl-Lewis X saccharides and mucin-like glycoproteins
What plays a vital role in leukocyte and platelet adhesion during inflammatory and hemostatic responses?
Integrins
Which junction is responsible for providing tissues with mechanical strength and is most abundant in tissues exposed to mechanical stress?
Desmosomes
What is the primary function of adherens junctions in early vertebrate development?
Causing controlled contraction of actin filament bundles
Which junction allows communication between cells within tissues by facilitating the free interchange of ions and larger molecules?
Gap junctions
What is the role of hemidesmosomes in diseases like bullous pemphigoid?
Attacking type XVII collagen
What do desmosomes contain on the cytoplasmic face of the junction, providing attachment sites for intermediate filaments?
Plaque-shaped structures
What is the function of gap junction permeability?
Facilitating the free interchange of ions and larger molecules
Which type of junction is used by cells to attach to the basal lamina?
Hemidesmosomes
What is the primary role of adherens junctions?
Providing mechanical strength
What is the main function of desmosomes?
Providing mechanical strength
What do hemidesmosomes anchor to?
Basal lamina
What is the primary function of gap junctions?
Facilitating cell communication
What is the main characteristic of adherens junctions in early vertebrate development?
Causing controlled contraction of actin filament bundles
Which type of cell junction forms a physical barrier known as the blood-brain barrier?
Tight junctions
What is the main component of tight junctions that forms an anastomosing network of protein strands?
Claudin
Which type of cell junction is responsible for maintaining the physical integrity of the epithelium near its apical surface?
Adherens junctions
What type of junction forms anchorage sites for intermediate filaments and holds cells together through transmembrane adhesion proteins?
Desmosomes
Which protein family forms adherens junctions and links neighboring cells together?
Cadherin
In which type of tissue does fascia adherens connect cardiomyocytes to one another?
Muscle tissue
What are the main components of tight junctions that restrict the diffusion of solutes?
Claudin and occludin
Which type of cell junction is also known as adhering junctions and functions in cell-to-cell adhesion?
Adherens junctions
What can mutations in claudin proteins cause?
Renal magnesium wasting syndrome and hereditary deafness
Which type of cell junction restricts the passage of molecules and separates the apical and basolateral domains of the plasma membrane?
Tight junctions
What is the function of adherens junctions in epithelial cells?
Linking neighboring cells together
Which type of cell junction plays crucial roles in the structure and function of various tissues, such as the epithelium and heart muscle?
Tight junctions
Which type of cell junction forms barriers to prevent the free passage of substances and cells from lumen to the blood circulation?
Occluding junctions (tight junctions)
In which type of tissues are cell-cell junctions abundant?
Epithelial tissues
What is the main function of cell-cell junctions?
Cell to cell attachment (adhesion)
Where are lateral surface modifications and junctional complexes found?
Lateral surface of epithelial cells
What is the main function of cell-cell junctions?
To form barriers that prevent the free passage of substances and cells from lumen to the blood circulation
Where are lateral surface modifications and junctional complexes found?
Lateral surface
Which type of cell junction forms barriers to prevent the free passage of substances and cells from lumen to the blood circulation?
Tight junctions
What regulates gap junctions?
Cell to cell communication
What is the primary function of cell-cell junctions in epithelial tissues?
To prevent the free passage of substances and cells from the lumen to the blood circulation
Which type of cell junction forms barriers that prevent the free passage of substances and cells from the lumen to the blood circulation?
Occluding junctions (tight junctions)
Which type of junction allows cell-to-cell communication within tissues by facilitating the free interchange of ions and larger molecules?
Gap junctions
What is the main function of lateral surface modifications in epithelial cells?
To enhance cell-cell adhesion
Study Notes
Cell Junctions and Adhesion Proteins
- Gap junctions consist of assemblies of six connexins, forming a hydrophilic channel allowing the passage of ions, molecules, and information between cells.
- Permeability of gap junctions allows the passage of ions, amino acids, nucleotides, sugars, and cyclic AMP through the channels, regulating the coordination of function in tissues.
- Gap junctions are regulated by posttranslational modification of connexins and environmental changes like cytosolic pH and free Ca2+ concentration.
- Mutations in connexin genes can cause human diseases, such as deafness, cataract, and heart malformations.
- Hemidesmosomes and focal adhesions are anchoring junctions that bind cells to the extracellular matrix, involving integrins and intermediate filaments.
- Hemidesmosomes have a single dense plaque anchoring intermediate filaments to the basal lamina, while mutations in plectin cause skin blisters.
- Focal adhesions bind cells to the extracellular matrix through integrins and indirectly to actin filaments in the cytoplasm.
- Anchoring junctions can be subclassified based on the cytoskeletal element involved, such as actin filament attachment sites and intermediate filament attachment sites.
- Adhesion proteins include cadherins, integrins, and other superfamilies like immunoglobulin superfamily members and selectins, mediating cell-cell adhesion and transient adhesions in the bloodstream.
- Selectins are calcium-dependent cell-surface carbohydrate-binding proteins, with major physiological roles in inflammatory and hemostatic responses, and in mediating lymphocyte binding to endothelium in peripheral lymph nodes.
- The selectin family includes L-selectin (leukocyte), E-selectin (endothelial), and P-selectin (platelet), and their ligands include sialyl-Lewis X saccharides and mucin-like glycoproteins.
- The adhesive binding mediated by selectins and integrins plays a vital role in leukocyte and platelet adhesion during inflammatory and hemostatic responses.
Cell Junctions and Their Functions
- Tight junctions are cell-to-cell junctions located just below the apical surface, preventing the passage of molecules and separating the apical and basolateral domains of the plasma membrane.
- Tight junctions consist of anastomosing network of protein strands, mainly composed of transmembrane proteins like claudin and occludin.
- Tight junctions restrict the diffusion of solutes larger than about 1.8 nm and are responsible for the blood-brain and blood-testes barriers.
- Endothelial cells of capillaries in the brain and spinal cord are joined by continuous tight junctions, forming a physical barrier called the blood-brain barrier.
- Mutations in claudin proteins can cause renal magnesium wasting syndrome and hereditary deafness.
- Anchoring junctions, also known as adhering junctions, function in cell-to-cell adhesion and binding of the cytoskeleton to the cell surface.
- Adherens junctions, like zonula adherens, surround the entire periphery of epithelial cells near their apical surface, maintaining the physical integrity of the epithelium.
- Desmosomes, or macula adherens, are anchorage sites for intermediate filaments and hold cells together through transmembrane adhesion proteins.
- Adherens junctions are formed by transmembrane adhesion proteins belonging to the cadherin family and link neighboring cells together.
- In heart muscle, a similar junction called fascia adherens connects cardiomyocytes to one another.
- Tight junctions and adherens junctions play crucial roles in the structure and function of various tissues, such as the epithelium and heart muscle.
- Understanding the composition and function of cell junctions is essential for comprehending the physiology and pathology of various tissues and organs.
Test your knowledge of cell junctions and adhesion proteins with this quiz. Learn about the functions of gap junctions, tight junctions, and anchoring junctions, as well as the roles of adhesion proteins like connexins, cadherins, and integrins. Explore how mutations in these proteins can lead to human diseases and understand the importance of these cellular structures in maintaining tissue integrity and function.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
