Cell Membrane and Organelles Quiz

Questions and Answers

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?

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?

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?

Their assembly is partially controlled through phosphorylation Signup and view all the answers

What is the role of α-Amanitin regarding actin filaments?

Inhibits the depolymerization of actin filaments Signup and view all the answers

What type of cells predominantly contain vimentin as an intermediate filament protein?

Fibroblasts and various epithelial cells in blood vessels Signup and view all the answers

What is the primary role of the plasma membrane in cellular function?

Separation of cytoplasm from interstitial fluid Signup and view all the answers

Which of the following best describes cell lysis?

Disruption of cell membrane leading to release of contents Signup and view all the answers

How do eukaryotic membranes contribute to cellular compartmentalization?

By segregating organ functions and intracellular events Signup and view all the answers

What property of eukaryotic membranes assists in selective permeability?

Presence of channels and pumps for ions and substrates Signup and view all the answers

What function does the cytoskeleton serve within eukaryotic cells?

Providing strength and structure to the cell Signup and view all the answers

Which process is facilitated by membranes for the exchange of materials between adjacent cells?

Gap junctions Signup and view all the answers

What can result from specific component deficiency or alteration in cellular membranes?

Disease states Signup and view all the answers

What is one of the clinical significances of gross alterations in eukaryotic membranes?

Disturbance of water balance and ion flux Signup and view all the answers

What role does the plasma membrane play in energy transduction?

Acts as a site for photosynthesis and oxidative phosphorylation Signup and view all the answers

What is the primary function of transmembrane proteins in the context of ion transport?

They form a pore that opens or closes in response to stimuli. Signup and view all the answers

Which type of ion channel is primarily responsible for the conduction of nerve impulses?

Voltage-gated channels Signup and view all the answers

What characterizes ligand-gated channels like CFTR?

They require a specific binding compound to open. Signup and view all the answers

What role does ATP play in the function of CFTR channels?

Only a few ATP molecules are used for ATP-dependent regulation. Signup and view all the answers

Which of the following statements best describes phosphorylation-gated channels?

They are regulated by the phosphorylation of their intracellular domain. Signup and view all the answers

What type of stimulus do pressure-gated channels primarily respond to?

Mechanical pressure or distortion Signup and view all the answers

Which ion is primarily transported through the CFTR channel?

Chloride (Cl-) Signup and view all the answers

What primarily triggers the opening of voltage-gated Na+ channels during nerve impulses?

Depolarization of the membrane Signup and view all the answers

In what way does the function of ligand-gated channels differ from that of voltage-gated channels?

Ligand-gated channels require the presence of specific compounds for activation. Signup and view all the answers

What characteristic distinguishes passive ion transport through voltage-gated channels?

It occurs via facilitated diffusion without energy input. Signup and view all the answers

What is the primary consequence of a mutation in the CFTR gene?

Accumulation of dried mucus in airways and pancreatic ducts Signup and view all the answers

How does cholera A toxin affect CFTR function in intestinal mucosal cells?

Indirectly activates phosphorylation of the regulatory domain via protein kinase A Signup and view all the answers

What role do G proteins play in association with G-Protein Coupled Receptors?

They function as relay molecules that transmit signals from activated receptors. Signup and view all the answers

What is the state of the G protein when the receptor is inactive?

The alpha subunit is bound to GDP. Signup and view all the answers

Which G protein class is responsible for increasing cAMP levels?

Gs Signup and view all the answers

What happens to the alpha subunit upon stimulation of the G-Protein Coupled Receptor?

It exchanges GDP for GTP and then dissociates from the βγ complex. Signup and view all the answers

Which G protein class activates phospholipase C (PLC)?

Gq Signup and view all the answers

What is a characteristic feature of G-Protein Coupled Receptors?

They contain seven transmembrane domains. Signup and view all the answers

What is the primary function of CFTR in relation to cholera?

To allow Cl- and H2O movement to the intestinal lumen. Signup and view all the answers

What is NOT a characteristic of inactive G proteins?

The beta subunit is active. Signup and view all the answers

What role does phosphorylation play in the function of CFTR?

It induces a conformational change that regulates channel activity. Signup and view all the answers

Which feature of CFTR contributes to its classification as a member of the ABC superfamily?

It has transmembrane domains connected to ATP binding sites. Signup and view all the answers

How do chloride ions move through the CFTR channel?

They passively diffuse through once the channel is open. Signup and view all the answers

What happens to the CFTR channel after ATP is hydrolyzed?

It reverts to its original conformation and closes. Signup and view all the answers

What kinetics are exhibited by many gated channels, including CFTR, at high concentrations of transported compounds?

Saturation kinetics indicating a maximum transport capacity. Signup and view all the answers

What is the primary function of the regulatory domain of CFTR?

To inhibit ATP binding until phosphorylated. Signup and view all the answers

What occurs to CFTR when it is phosphorylated by a kinase?

The regulatory domain moves away from the ATP binding domains. Signup and view all the answers

In what condition does CFTR play a significant role?

Chloride ion transport related to cystic fibrosis. Signup and view all the answers

Why is CFTR's channel described as regulated through phosphorylation?

It changes the conformation, allowing ion flow only when activated. Signup and view all the answers

Which statement best describes the transmembrane domains of CFTR?

They form a closed channel that opens when ATP binds. Signup and view all the answers

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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Description

Test your knowledge on the structure and function of the cell membrane and its role in cell lysis. This quiz covers key concepts related to plasma membranes and organelles. Enhance your understanding of cellular biology and the importance of membrane integrity.