All flashcards
Flashcard 1: Which ECM protein is the major tensile-strength component of connective tissue?
Answer: Collagen. Its triple-helical structure resists stretching, forming fibrils that support tissue architecture.
Flashcard 2: Which ECM protein commonly mediates cell attachment by binding integrins (RGD motif)?
Answer: Fibronectin. It links cells to collagen via integrin-binding domains, facilitating migration and organization.
Flashcard 3: Which basement membrane protein forms a sheet-like network and binds integrins?
Answer: Laminin. It self-assembles into networks that organize basement membranes and support epithelial attachment.
Flashcard 4: What is the basement membrane (basal lamina) primarily composed of?
Answer: Laminin, type IV collagen, proteoglycans, and nidogen. These components form a thin, organized sheet separating epithelia from connective tissue.
Flashcard 5: What is a proteoglycan in the ECM?
Answer: Core protein covalently linked to glycosaminoglycan (GAG) chains. This structure allows proteoglycans to attract water and ions, contributing to ECM hydration.
Flashcard 6: Which ECM component provides hydration and resistance to compression in cartilage?
Answer: Proteoglycans and GAGs (for example, aggrecan, hyaluronan). Their negatively charged GAGs bind water, creating a hydrated gel that absorbs compressive forces.
Flashcard 7: Identify the junction type: Ca2+-dependent cadherins connect cells to actin belts.
Answer: Adherens junction. This junction forms a belt-like structure for circumferential adhesion and cytoskeletal linkage.
Flashcard 8: Identify the junction type: protein channels allow ion flow and electrical coupling.
Answer: Gap junction. It facilitates rapid signaling and synchronization in tissues like cardiac muscle.
Flashcard 9: What is the primary function of tight junctions (zonula occludens) in epithelia?
Answer: Seal adjacent cells to block paracellular transport and maintain polarity. They form a barrier at the apical-lateral border, preventing diffusion between cells and separating membrane domains.
Flashcard 10: Which cytoskeletal element is anchored at adherens junctions?
Answer: Actin microfilaments. Catenins link cadherins to the actin cytoskeleton, enabling force transmission and cell shape maintenance.
Flashcard 11: Which Ca2+-dependent adhesion proteins mediate adherens junctions?
Answer: Cadherins (for example, E-cadherin). These proteins homophilically bind across cells in a calcium-dependent manner to facilitate adhesion.
Flashcard 12: What is the key function of adherens junctions (zonula adherens) between cells?
Answer: Cell–cell adhesion via actin-linked cadherins. They provide mechanical linkage and maintain tissue integrity by connecting cytoskeletons of neighboring cells.
Flashcard 13: What cytoskeletal element is linked to tight junctions via ZO proteins?
Answer: Actin microfilaments. ZO proteins act as scaffolds connecting transmembrane components to the cytoskeleton for structural support.
Flashcard 14: Which transmembrane proteins form the sealing strands of tight junctions?
Answer: Claudins and occludin. These proteins create the tight seal by forming extracellular interactions between adjacent cell membranes.
Flashcard 15: What is the primary function of desmosomes (macula adherens)?
Answer: Strong cell–cell adhesion resisting mechanical stress. They distribute mechanical forces across tissues by anchoring intermediate filaments between cells.
Flashcard 16: Which intermediate filaments are classically anchored to desmosomes in epithelia?
Answer: Keratin intermediate filaments. These filaments provide tensile strength and resilience, linking to desmosomes via plaque proteins.
Flashcard 17: Which cadherin-family proteins are the transmembrane components of desmosomes?
Answer: Desmoglein and desmocollin. These proteins form transcellular dimers, anchoring cytoskeletal elements for robust adhesion.
Flashcard 18: What is the primary function of gap junctions between animal cells?
Answer: Direct intercellular passage of ions and small molecules. They enable metabolic and electrical coupling by forming aqueous pores between cytoplasms.
Flashcard 19: Which protein subunits assemble to form a connexon in a gap junction?
Answer: Connexins. Six connexins form a hemichannel (connexon) that docks with an adjacent cell's to create the pore.
Flashcard 20: What is the typical maximum size limit for molecules passing through gap junctions?
Answer: Approximately <1 kDa. The channel pore size restricts passage to small solutes, ensuring selective communication.
Flashcard 21: What is the primary function of hemidesmosomes?
Answer: Anchor epithelial cells to the basement membrane (ECM). They provide stable attachment to the underlying ECM, maintaining epithelial integrity.
Flashcard 22: Which transmembrane receptor links hemidesmosomes to the extracellular matrix?
Answer: Integrins. These receptors bind ECM ligands like laminin, connecting to intracellular adapters.
Flashcard 23: Which cytoskeletal element is anchored by hemidesmosomes inside the cell?
Answer: Intermediate filaments (keratin). They link to plaque proteins like plectin, providing mechanical stability against shear forces.
Flashcard 24: What is the defining feature of integrins regarding ligand binding and signaling?
Answer: Bidirectional signaling: inside-out and outside-in. Integrins transmit signals from ECM to cytoskeleton and vice versa, regulating adhesion and migration.
Flashcard 25: What is the main function of the extracellular matrix (ECM) in animal tissues?
Answer: Structural support, signaling, and regulation of cell behavior. ECM provides a scaffold for cells, influences differentiation, and modulates growth factor activity.