intermediate filaments Flashcards
(37 cards)
Describe the role of actin in eukaryotic cells.
Actin is the most abundant intracellular protein in eukaryotic cells, playing a crucial role in various cellular processes such as muscle contraction, cell movement, and local restructuring of the cell.
Explain the difference between G-actin and F-actin.
G-actin is the globular monomeric form of actin, while F-actin is the filamentous polymerized form that consists of multiple G-actin monomers.
How do actin microfilaments contribute to cell movement?
Actin microfilaments allow for rapid assembly and disassembly, enabling cells to extend and contract, which is essential for movement.
Define the structure of actin microfilaments in parallel bundles.
Actin microfilaments in parallel bundles are arranged in the same direction and close together, often found in structures like spikes and filopodia, and are cross-linked by proteins such as fimbrin and villin.
What happens to actin microfilaments when myosin motors are fixed in place?
When myosin motors are fixed, pulling one parallel fiber relative to another results in movement, demonstrating the interaction between actin and myosin.
Describe the role of filamin in actin networks.
Filamin is a cross-linker protein that connects multiple actin filaments, forming loose elastic networks that are important for cell shape and movement.
Explain the process of phagocytosis in relation to actin.
Phagocytosis is an actin-mediated process where cells, such as macrophages and neutrophils, surround and engulf large particles like bacteria or dead cells.
How does the loss of filamin affect cell movement?
The loss of filamin results in the inability of cells to move, as it disrupts the actin network necessary for cellular extension and contraction.
What is the function of microtubules in eukaryotic cells?
Microtubules serve various functions, including forming the motile components of cilia and flagella, aiding in chromosome separation during mitosis, and providing structural support for cell shape and organelle positioning.
Describe the assembly process of microtubules.
Microtubules grow and shrink from their plus end, while their minus end is stabilized by the centrosome, allowing for dynamic changes in their length.
What are microtubule-associated proteins (MAPs) and their effects?
MAPs are proteins that cross-link microtubules to form bundles, increasing their stability, altering rigidity, or changing the rate of assembly, thus affecting microtubule dynamics.
How do drugs like Taxol affect microtubules?
Taxol disrupts microtubule dynamics by stabilizing them, which is used in cancer treatment to target rapidly dividing cells.
Describe the role of Paclitaxel in cell division.
Paclitaxel binds to microtubules (MTs) and stabilizes them, preventing depolymerization, which arrests cells in mitosis and disrupts the movement of organelles and molecules.
Explain the structure of intermediate filaments.
Intermediate filaments have a common structure consisting of a central alpha helical core flanked by globular N and C terminal domains, with the core containing four long helices and three non-helical spacers.
How do intermediate filaments contribute to cellular integrity?
Intermediate filaments provide mechanical support for membranes, form an internal framework to support cell shape and resilience, and are anchored at specialized cell junctions, helping to maintain cell integrity.
Define Epidermolysis bullosa simplex (EBS).
EBS is a human disease caused by mutant keratin proteins, leading to blistering due to fragile skin cells that easily damage and cause overlying layers to delaminate.
Compare the mechanical properties of microtubules, actin microfilaments, and intermediate filaments.
Microtubules are easily deformed but cannot be stretched without rupture, actin microfilaments are more rigid and can stretch but rupture easily, while intermediate filaments are flexible and can withstand large mechanical stresses, making them best for maintaining cell integrity.
How do cells form tissues?
Cells anchor to other cells and/or to surrounding material, forming tissues that consist of cells plus a network of molecules in the intercellular space, filled with proteins and sugars secreted by the cells.
What are the types of junctions between cells?
The types of junctions between cells include anchor junctions, occluding junctions, channel-forming junctions, and signal relay junctions.
Explain the function of adherens junctions.
Adherens junctions consist of intracellular actin filaments and trans-membrane cadherins that tie neighboring cells together, with cadherins mediating homophilic adhesion in a Ca2+ dependent manner.
Describe the role of desmosomes in cell adhesion.
Desmosomes are junctions that involve intracellular intermediate filaments and trans-membrane non-classical cadherins, such as desmoglein and desmocollin, providing strong adhesion between cells.
How are intermediate filaments connected to microtubules?
Intermediate filaments may be connected to microtubules, often showing a similar spatial pattern, which helps in maintaining cellular structure and integrity.
Describe the function of tight junctions in epithelial layers.
Tight junctions allow epithelial layers to function as barriers by sealing tightly across adjacent plasma membranes, regulating permeability.
Explain how tight junctions can be regulated by the body.
Cells can transiently regulate the tightness of tight junctions in response to factors such as nutrients after a meal, intestinal bacteria, gluten, and immune cells.
