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Questions and Answers
What is the primary function of stress fibers in epithelial cells?
What is the primary function of stress fibers in epithelial cells?
- To provide energy for cellular processes
- To form a protective barrier against pathogens
- To permit reaction to external stresses as a cellular sheet (correct)
- To facilitate communication between cells via gap junctions
What is the consequence of Cytochalasin B's action on microfilaments?
What is the consequence of Cytochalasin B's action on microfilaments?
- Promotes cell division via spindle fiber formation
- Stimulates the polymerization of actin filaments
- Inhibits microfilament assembly leading to cell shape alteration (correct)
- Enhances cell motility and shape flexibility
How do intermediate filaments structurally differ from microfilaments?
How do intermediate filaments structurally differ from microfilaments?
- Intermediate filaments are approximately 10 nm in diameter and consist of fibrous proteins (correct)
- Intermediate filaments exclusively mediate cell signaling processes
- Intermediate filaments are composed of actin, while microfilaments are made of keratin
- Intermediate filaments form dynamic structures, whereas microfilaments are static
Which characteristic is true for the assembly of intermediate filaments?
Which characteristic is true for the assembly of intermediate filaments?
What is the role of α-Amanitin regarding actin filaments?
What is the role of α-Amanitin regarding actin filaments?
What type of cells predominantly contain vimentin as an intermediate filament protein?
What type of cells predominantly contain vimentin as an intermediate filament protein?
What is the primary role of the plasma membrane in cellular function?
What is the primary role of the plasma membrane in cellular function?
Which of the following best describes cell lysis?
Which of the following best describes cell lysis?
How do eukaryotic membranes contribute to cellular compartmentalization?
How do eukaryotic membranes contribute to cellular compartmentalization?
What property of eukaryotic membranes assists in selective permeability?
What property of eukaryotic membranes assists in selective permeability?
What function does the cytoskeleton serve within eukaryotic cells?
What function does the cytoskeleton serve within eukaryotic cells?
Which process is facilitated by membranes for the exchange of materials between adjacent cells?
Which process is facilitated by membranes for the exchange of materials between adjacent cells?
What can result from specific component deficiency or alteration in cellular membranes?
What can result from specific component deficiency or alteration in cellular membranes?
What is one of the clinical significances of gross alterations in eukaryotic membranes?
What is one of the clinical significances of gross alterations in eukaryotic membranes?
What role does the plasma membrane play in energy transduction?
What role does the plasma membrane play in energy transduction?
What is the primary function of transmembrane proteins in the context of ion transport?
What is the primary function of transmembrane proteins in the context of ion transport?
Which type of ion channel is primarily responsible for the conduction of nerve impulses?
Which type of ion channel is primarily responsible for the conduction of nerve impulses?
What characterizes ligand-gated channels like CFTR?
What characterizes ligand-gated channels like CFTR?
What role does ATP play in the function of CFTR channels?
What role does ATP play in the function of CFTR channels?
Which of the following statements best describes phosphorylation-gated channels?
Which of the following statements best describes phosphorylation-gated channels?
What type of stimulus do pressure-gated channels primarily respond to?
What type of stimulus do pressure-gated channels primarily respond to?
Which ion is primarily transported through the CFTR channel?
Which ion is primarily transported through the CFTR channel?
What primarily triggers the opening of voltage-gated Na+ channels during nerve impulses?
What primarily triggers the opening of voltage-gated Na+ channels during nerve impulses?
In what way does the function of ligand-gated channels differ from that of voltage-gated channels?
In what way does the function of ligand-gated channels differ from that of voltage-gated channels?
What characteristic distinguishes passive ion transport through voltage-gated channels?
What characteristic distinguishes passive ion transport through voltage-gated channels?
What is the primary consequence of a mutation in the CFTR gene?
What is the primary consequence of a mutation in the CFTR gene?
How does cholera A toxin affect CFTR function in intestinal mucosal cells?
How does cholera A toxin affect CFTR function in intestinal mucosal cells?
What role do G proteins play in association with G-Protein Coupled Receptors?
What role do G proteins play in association with G-Protein Coupled Receptors?
What is the state of the G protein when the receptor is inactive?
What is the state of the G protein when the receptor is inactive?
Which G protein class is responsible for increasing cAMP levels?
Which G protein class is responsible for increasing cAMP levels?
What happens to the alpha subunit upon stimulation of the G-Protein Coupled Receptor?
What happens to the alpha subunit upon stimulation of the G-Protein Coupled Receptor?
Which G protein class activates phospholipase C (PLC)?
Which G protein class activates phospholipase C (PLC)?
What is a characteristic feature of G-Protein Coupled Receptors?
What is a characteristic feature of G-Protein Coupled Receptors?
What is the primary function of CFTR in relation to cholera?
What is the primary function of CFTR in relation to cholera?
What is NOT a characteristic of inactive G proteins?
What is NOT a characteristic of inactive G proteins?
What role does phosphorylation play in the function of CFTR?
What role does phosphorylation play in the function of CFTR?
Which feature of CFTR contributes to its classification as a member of the ABC superfamily?
Which feature of CFTR contributes to its classification as a member of the ABC superfamily?
How do chloride ions move through the CFTR channel?
How do chloride ions move through the CFTR channel?
What happens to the CFTR channel after ATP is hydrolyzed?
What happens to the CFTR channel after ATP is hydrolyzed?
What kinetics are exhibited by many gated channels, including CFTR, at high concentrations of transported compounds?
What kinetics are exhibited by many gated channels, including CFTR, at high concentrations of transported compounds?
What is the primary function of the regulatory domain of CFTR?
What is the primary function of the regulatory domain of CFTR?
What occurs to CFTR when it is phosphorylated by a kinase?
What occurs to CFTR when it is phosphorylated by a kinase?
In what condition does CFTR play a significant role?
In what condition does CFTR play a significant role?
Why is CFTR's channel described as regulated through phosphorylation?
Why is CFTR's channel described as regulated through phosphorylation?
Which statement best describes the transmembrane domains of CFTR?
Which statement best describes the transmembrane domains of CFTR?
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Study Notes
Plasma/Cell Membrane
- Separates cytoplasm from interstitial fluid; maintains equilibrium with plasma.
- Also referred to as the limiting membrane.
Cell Lysis
- Refers to the breaking of the cell membrane, leading to the release of cellular contents.
- Occurs when the cell membrane's continuity is disrupted.
Organelles
- Comprise distinct internal membranous structures or compartments within the cell.
Cytoskeleton
- Provides structural integrity and strength to the cell.
- Controls intracellular movement and contributes to extracellular motility.
Eukaryotic Membranes Functions
- Compartmentalize and segregate intracellular events, separating different cell functions.
- Act as selective barriers, regulating cellular functions and localizing specific enzyme systems.
- Provide a semisolid phase in an aqueous environment and enable material exchange via endo- and exocytosis.
- Facilitate communication between adjacent cells through gap junctions.
- Serve as sites for energy transduction processes like photosynthesis and oxidative phosphorylation.
Clinical Significance
- Gross alterations can disrupt water balance and ion flux, impacting cellular health.
- Specific component deficiencies or alterations are linked to various disease states.
Mechanism of Action
- Transmembrane proteins create pores for ion transport, influenced by stimuli such as voltage changes and ligand binding.
- Voltage-gated channels (e.g., sodium channels) respond to membrane depolarization, crucial for nerve impulse conduction.
- Ligand-gated channels (e.g., CFTR for chloride ions) enable diffusion regulated by ligand binding and involve minimal ATP consumption.
- Phosphorylation-gated channels (e.g., CFTR) alter conformation to regulate ion flow based on phosphate attachment and ATP hydrolysis.
Cystic Fibrosis Transmembrane Conductance Regulator (CFTR)
- Essential in cystic fibrosis; mutations result in mucus accumulation in airways and pancreatic ducts.
- In cholera, CFTR is activated, causing excessive Cl- and H2O to flow into the intestinal lumen, leading to dehydration.
G-Protein Coupled Receptors (GPCRs)
- The primary class of cell membrane receptors, crossing the membrane seven times.
- Coupled with trimeric GTP-binding proteins for intracellular signaling; inactive when bound to GDP.
- Upon stimulation, the receptor allows the α subunit to exchange GDP for GTP, activating target proteins.
G-Protein Types
- Gs: Stimulatory protein increasing cAMP levels.
- Gi: Inhibitory protein decreasing cAMP levels.
- Gq: Activates phospholipase C, impacting various signaling pathways.
Vesicular Transport Across the Plasma Membrane
- Stress fibers act as circumferential belts around epithelial cell surfaces, aiding in response to external stress.
- Actin-Myosin II bundles form during cytokinesis as a contractile ring to separate dividing cells.
Drugs Affecting Microfilaments
- Cytochalasin B inhibits microfilament assembly, altering cell shape and movement.
- Phalloidin prevents depolymerization of actin filaments, maintaining structure.
- α-Amanitin interferes with various cellular functions related to filament dynamics.
Intermediate Filaments
- Roughly 10 nm in diameter, made of fibrous protein polymers for structural support.
- Formed from coiling α-helical segments, facilitating self-assembly into stable structures.
- Five major classes are identified based on protein subunit types (e.g., Vimentin found in fibroblasts and blood vessel epithelium).
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