Lecture 3
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Questions and Answers

What term describes the process by which organisms maintain a relatively stable internal environment?

  • Equilibrium
  • Homeostasis (correct)
  • Diffusion
  • Osmosis

    • Which of the following is NOT a key concept associated with homeostasis?

  • Intracellular fluid (ICF)
  • Dynamic steady state
  • Absolute equilibrium (correct)
  • Extracellular fluid (ECF)

    • In multicellular organisms, what is essential for maintaining homeostasis at the cellular level?

  • Unregulated cell growth
  • Cellular isolation
  • Random cell migration
  • Intercellular communication (correct)

    • Which of the following represents the primary role of intercellular communication?

    <p>Enabling cell survival, division, differentiation, and death</p> Signup and view all the answers

    What are the two basic types of signals cells use for intercellular communication?

    <p>Electrical and Chemical</p> Signup and view all the answers

    What happens if an organism's compensatory mechanism is NOT successful when homeostasis is disrupted?

    <p>Homeostasis is further disrupted, possibly leading to disease</p> Signup and view all the answers

    Which term describes cells that respond to either electrical or chemical signals?

    <p>Target cells</p> Signup and view all the answers

    What is the extracellular fluid (ECF)'s function in relation to homeostasis?

    <p>To serve as a link between cells and the external environment</p> Signup and view all the answers

    What is the immediate effect of a ligand binding to a cell-surface receptor?

    <p>Change in receptor conformation</p> Signup and view all the answers

    Which factor primarily determines the type of ion channel that will be activated?

    <p>The type of stimuli present</p> Signup and view all the answers

    What property defines the 'selectivity' of an ion channel?

    <p>The specific types of ions it allows to pass through</p> Signup and view all the answers

    What is the primary function of protein kinases?

    <p>To phosphorylate specific proteins.</p> Signup and view all the answers

    A voltage-gated ion channel is least likely to be open when:

    <p>The cell membrane is polarized.</p> Signup and view all the answers

    What is the primary function of ligand-gated ion channels in neural communication?

    <p>To convert chemical signals into electrical signals</p> Signup and view all the answers

    Which subunit of a G protein is most crucial for determining the specificity of signal transduction?

    <p>The alpha (α) subunit</p> Signup and view all the answers

    In the inactive state of a G protein, which molecule is bound to the alpha (α) subunit?

    <p>GDP</p> Signup and view all the answers

    Which of the following is NOT a typical outcome of ion channel activation following neurotransmitter binding?

    <p>Increased synthesis of neurotransmitter molecules.</p> Signup and view all the answers

    What two molecules are created after the activation of a G protein when GTP replaces GDP??

    <p>The α-subunit linked to GTP and the βγ complex.</p> Signup and view all the answers

    How do G protein-coupled receptors (GPCRs) generally differ from ion channel-coupled receptors in their signaling action?

    <p>GPCRs transmit signals through secondary signaling molecules.</p> Signup and view all the answers

    Which of the following is NOT a typical target of G proteins?

    <p>Protein kinase</p> Signup and view all the answers

    What is an important characteristic of an ion channel in its role as a cell receptor?

    <p>Fast response to stimuli.</p> Signup and view all the answers

    What is the second messenger molecule formed by adenylyl cyclase?

    <p>cAMP</p> Signup and view all the answers

    Which of these ligands can cause the activation of adenylyl cyclase?

    <p>Glucagon</p> Signup and view all the answers

    What two molecules are produced by the activation of phospholipase C?

    <p>IP3 and DAG</p> Signup and view all the answers

    Which of the following is NOT a characteristic of ligands that bind to intracellular receptors?

    <p>Large and hydrophilic</p> Signup and view all the answers

    In its active state, where are intracellular receptors primarily located?

    <p>Nucleus</p> Signup and view all the answers

    What type of cellular communication involves direct contact between cells for signal transfer?

    <p>Juxtacrine</p> Signup and view all the answers

    Which domain of a nuclear receptor is responsible for interacting with specific DNA sequences?

    <p>DNA binding domain (DBD)</p> Signup and view all the answers

    What is the typical length of the hormone response element (HRE) sequence?

    <p>15 nucleotides</p> Signup and view all the answers

    Which communication method involves molecules released by a cell acting on neighboring cells through the extracellular fluid?

    <p>Paracrine</p> Signup and view all the answers

    In autocrine communication, where do the released molecules exert their effect?

    <p>On the same cell that released them</p> Signup and view all the answers

    What term describes a nuclear receptor composed of two different protein subunits?

    <p>Heterodimer</p> Signup and view all the answers

    What is the primary means of signal distribution in endocrine communication?

    <p>The circulatory system via the bloodstream</p> Signup and view all the answers

    Which of the following is NOT a family of receptors included in the intracellular receptor category?

    <p>Receptors for growth factors</p> Signup and view all the answers

    Which of these is a characteristic associated with cell-surface receptors?

    <p>Binding of large, hydrophilic or charged molecules</p> Signup and view all the answers

    Which system uses a combination of electrical and chemical signals to communicate over long distances?

    <p>The nervous system</p> Signup and view all the answers

    How do neurotransmitters differ from neurohormones in their mode of action?

    <p>Neurotransmitters have a fast, localized effect by diffusing across the synaptic cleft, while neurohormones travel through the bloodstream for a slower effect.</p> Signup and view all the answers

    How do ion channel-linked receptors affect the cell membrane?

    <p>They cause a change in membrane potential and permeability to specific ions</p> Signup and view all the answers

    In neuronal communication, what type of signal is converted into a chemical signal at the end of the neuron?

    <p>Electrical signal</p> Signup and view all the answers

    What is the function of cellular receptors in cell communication?

    <p>To receive, transform, and transmit information from the external environment</p> Signup and view all the answers

    Which of the following is a characteristic of enzyme-linked receptors?

    <p>Their activation typically involves multiple intracellular transduction steps.</p> Signup and view all the answers

    Which of the following is NOT a functional type of enzyme-linked receptor?

    <p>Lipid kinase</p> Signup and view all the answers

    What process directly follows the binding of a ligand to a tyrosine kinase receptor?

    <p>Formation of a receptor dimer.</p> Signup and view all the answers

    What is the role of tyrosine residues in the activation of tyrosine kinases?

    <p>They are involved in mutual phosphorylation during receptor dimerization.</p> Signup and view all the answers

    Which of the following describes the Ras protein in its active state?

    <p>Bound to GTP</p> Signup and view all the answers

    How is the Ras protein activated?

    <p>By an adaptor protein binding a GEF protein, causing GDP to be replaced by GTP.</p> Signup and view all the answers

    What is the function of the phosphorylation cascade triggered by activated Ras?

    <p>To amplify the signal through phosphorylation of downstream kinases.</p> Signup and view all the answers

    What is the role of MAP kinase in the signaling cascade?

    <p>It phosphorylates target proteins to produce a cellular response.</p> Signup and view all the answers

    Which type of communication requires direct cell-to-cell contact?

    <p>Juxtacrine communication</p> Signup and view all the answers

    In which type of communication do signaling molecules act on the same cell that released them?

    <p>Autocrine communication</p> Signup and view all the answers

    What characterizes endocrine communication?

    <p>Signaling molecules are transported via the bloodstream</p> Signup and view all the answers

    Which type of molecule does neuronal communication primarily utilize?

    <p>Neurotransmitters and neurohormones</p> Signup and view all the answers

    What defines paracrine communication?

    <p>It affects only neighboring cells through the extracellular fluid.</p> Signup and view all the answers

    What is the primary effect of neurotransmitters in synaptic communication?

    <p>To diffuse across the synaptic cleft rapidly</p> Signup and view all the answers

    In which type of communication do signaling molecules travel long distances through the circulatory system?

    <p>Endocrine communication</p> Signup and view all the answers

    Which cells are primarily affected by hormones in endocrine communication?

    <p>Specific target cells with appropriate receptors</p> Signup and view all the answers

    What is a characteristic feature of enzyme-linked receptors?

    <p>They have effects that may require multiple intracellular transduction steps.</p> Signup and view all the answers

    What is the first stage in the action of tyrosine kinases?

    <p>Binding of signaling proteins to the receptor.</p> Signup and view all the answers

    What characteristic of a signaling molecule determines whether it can pass through the cell membrane?

    <p>Hydrophobicity</p> Signup and view all the answers

    What is NOT a potential consequence of ligand binding to a receptor?

    <p>Day-night cycle change</p> Signup and view all the answers

    How does the Ras protein become activated?

    <p>By converting GDP to GTP via a GEF protein.</p> Signup and view all the answers

    Which type of receptor is responsible for binding hydrophobic signaling molecules?

    <p>Intracellular receptors</p> Signup and view all the answers

    Which of the following best describes the role of MAP kinase in the phosphorylation cascade?

    <p>It is involved in the phosphorylation of target proteins.</p> Signup and view all the answers

    In which way can a single signaling molecule affect different target cells?

    <p>Different receptors on different cells</p> Signup and view all the answers

    What is a key function of tyrosine kinases?

    <p>They induce a change in gene expression.</p> Signup and view all the answers

    Which of the following accurately describes antagonists in cellular signaling?

    <p>They inhibit receptor activity</p> Signup and view all the answers

    Which ligands are known to activate tyrosine kinases?

    <p>FGF, EGF, PDGF, and VEGF.</p> Signup and view all the answers

    What type of signaling molecules do NOT require the presence of a receptor on the target cell to exert their effect?

    <p>Small and hydrophobic molecules</p> Signup and view all the answers

    What type of protein is predominantly activated by most tyrosine kinases?

    <p>Ras proteins.</p> Signup and view all the answers

    Which category includes signaling molecules that are typically unable to cross the cell membrane?

    <p>Hydrophilic signaling molecules</p> Signup and view all the answers

    What is the state of Ras protein when it is inactive?

    <p>It is bound to GDP.</p> Signup and view all the answers

    Which of the following definitions correctly describes ligands in terms of their function?

    <p>They act as signaling molecules that bind to receptors</p> Signup and view all the answers

    What occurs when homeostasis is disrupted and compensation is unsuccessful?

    <p>The organism may develop a disease</p> Signup and view all the answers

    Which compartment serves as a link between the external environment and cells in the context of homeostasis?

    <p>Extracellular fluid (ECF)</p> Signup and view all the answers

    How do cells communicate to maintain homeostasis in multicellular organisms?

    <p>Through intercellular communication or signaling</p> Signup and view all the answers

    What characterizes a dynamic steady state in homeostasis?

    <p>Constant movement and imbalance of substances</p> Signup and view all the answers

    What is the primary role of electrical signals in cell communication?

    <p>To trigger changes in the cell's membrane potential</p> Signup and view all the answers

    Which of the following statements about intercellular signaling is true?

    <p>Both electrical and chemical signals can initiate a response in target cells</p> Signup and view all the answers

    Which level of coordination is essential for maintaining homeostasis in multicellular organisms?

    <p>Across cells, tissues, and entire systems</p> Signup and view all the answers

    What type of environment do cells within tissues maintain to achieve homeostasis?

    <p>A relatively stable internal environment overall</p> Signup and view all the answers

    What role does a ligand play in the process of signal transduction?

    <p>It binds to a specific receptor on the target cell membrane.</p> Signup and view all the answers

    How does the activation of G proteins occur?

    <p>By the exchange of GDP for GTP.</p> Signup and view all the answers

    What describes the conformational change in 7TM receptors upon ligand binding?

    <p>It induces further signaling within the cell.</p> Signup and view all the answers

    What mechanism is primarily responsible for the switch-like behavior of molecular switches?

    <p>Phosphorylation and dephosphorylation.</p> Signup and view all the answers

    Which outcome is part of the signaling cascade within the cell?

    <p>Activation or inactivation of an enzyme.</p> Signup and view all the answers

    What is the primary characteristic of G protein-coupled receptors (GPCRs)?

    <p>They consist of seven transmembrane (7TM) domains.</p> Signup and view all the answers

    What is the role of intracellular signaling molecules in the context of a signaling cascade?

    <p>They propagate the signal deeper into the cell.</p> Signup and view all the answers

    How do molecular switches maintain their active state?

    <p>Through prolonged GTP binding.</p> Signup and view all the answers

    What is the primary function of intracellular receptors?

    <p>Regulate gene expression</p> Signup and view all the answers

    Which component is NOT part of the nuclear receptor structure?

    <p>Signal transducing domain</p> Signup and view all the answers

    What type of dimer is typically formed by most nuclear receptors?

    <p>Both B and C</p> Signup and view all the answers

    Which of the following ligands can bind to intracellular receptors?

    <p>Cortisol</p> Signup and view all the answers

    In which cellular location do intracellular receptors primarily function when active?

    <p>Nucleus</p> Signup and view all the answers

    Which of these best describes the hormone response element (HRE)?

    <p>A 15-nucleotide sequence within the nucleus</p> Signup and view all the answers

    How do cell-surface receptors differ from intracellular receptors in terms of ligand characteristics?

    <p>Cell-surface receptors bind large, hydrophilic molecules</p> Signup and view all the answers

    Which ion would most likely pass through an opened ion channel linked to a receptor?

    <p>Calcium ions (Ca2+)</p> Signup and view all the answers

    Intracellular receptors are divided into which of the following categories?

    <p>Nuclear receptors and cytoplasmic receptors</p> Signup and view all the answers

    Cell surface receptors are divided into which of the following categories?

    <p>All of the above</p> Signup and view all the answers

    Signup and view all the answers

    Study Notes

    Cell Signaling

    • Lecturer: Dr. Michelle Kuzma
    • Adapted from: Dr. Danuta Mielżyńska-Švach
    • Course: Molecular Biology
    • Academic Year: 2024/2025

    Homeostasis

    • Organism maintains a stable internal environment, despite external variability.
    • Homeostasis is the process of maintaining this stability.
    • Homeostatic disruption triggers compensatory mechanisms.
    • Successful compensation restores homeostasis.
    • Unsuccessful compensation can result in disease.

    Homeostasis Overview

    • External change causes internal change.
    • An organism in homeostasis is affected by internal change.
    • Internal change results in a loss of homeostasis.
    • The organism attempts to compensate for the internal changes.
    • Compensation can be successful or unsuccessful.
    • If successful, homeostasis is restored.
    • If unsuccessful, homeostasis remains disrupted and can lead to illness or disease.

    Components Associated with Homeostasis

    • Extracellular Fluid (ECF): A fluid environment that surrounds cells and connects the external environment to cells.
    • Intracellular Fluid (ICF): Fluid inside the cells.
    • Intracellular Fluid (ICF): Includes fluid within the cell (intracellular) and fluid within the blood vessels (intravascular).
    • ECF and ICF maintain relatively stable composition, but have dynamic steady states, not equilibrium.
    • Imbalances exist in concentrations of certain substances (e.g., Na+, Cl-, K+) between ECF and ICF.

    Role of Homeostasis in Multicellular Organisms

    • Coordination is necessary between cells, tissues, and organs to maintain homeostasis.
    • Intercellular communication is crucial for this coordination and is achieved through cell signaling.

    Intercellular Communication

    • Essential for cell survival, division, differentiation, and death.
    • Involves transmission of signals.

    Types of Signals

    • Electrical signals: Related to changes in the cell's membrane potential.
    • Chemical signals: Chemical compounds (molecules) secreted into the extracellular space.
    • Target cells respond to these signals.

    Methods of Communication

    • Local communication:
      • Juxtacrine communication: Direct contact between cells via gap junctions.
      • Paracrine communication: Signals act on neighboring cells.
      • Autocrine communication: Signals act on the same cell that secreted them.
    • Distant communication:
      • Endocrine communication: Hormones travel via the circulatory system to affect target cells throughout the body.
      • Neuronal communication: Combination of electrical and chemical signals used to communicate over long distances.

    Types of Cell Communication (Detailed)

    • Juxtacrine: Direct cell-cell contact; Molecules are transferred across gap junctions in adjacent cells.
    • Paracrine: Signals act on nearby cells.
    • Autocrine: Signals act on the same cell that released them.
    • Endocrine: Signals circulate through the bloodstream to affect distant target cells.
    • Synaptic/Neuronal: Signal released across a synapse, a specialized junction between two nerve cells, for short-distance communication between neurons.

    Types of Cell Signaling (Specific Definitions)

    • Juxtacrine: Signaling molecule on one cell binds to receptor on a neighboring cell (in contact).
    • Paracrine: A cell releases a molecule to act on a neighboring cell.
    • Autocrine: A cell releases a molecule to act on itself.
    • Endocrine: A hormone is released into the bloodstream to affect distant cells.
    • Synaptic/Neuronal: Neurotransmitters released across a synapse.

    Signal Molecules (Examples)

    • Hormones: (Epinephrine, cortisol, estradiol, insulin, testosterone, thyroid hormone)
    • Neurotransmitters: (Acetylcholine, γ-aminobutyric acid (GABA))

    Cell Communication Principles

    • Only cells with receptors respond to signals (selective response).
    • The cell's response depends on the cell's specialization and receptor type.
    • One signal molecule can have different effects on different cells.
    • One signal molecule can produce multiple effects in a single cell.

    Intercellular Communication principles

    • Signaling molecules (ligands) bind to receptors.
    • Binding of ligand to receptor can upregulate, downregulate, or activate the receptor.
    • The activated receptor triggers intracellular signaling.
    • The final signaling molecule triggers the final response (e.g., protein modification, synthesis).

    Types of Signaling Molecules

    • Pass through the cell membrane: Small, hydrophobic molecules. Intracellular receptors are required.
    • Do not pass through the cell membrane: Large, hydrophilic molecules. Cell surface receptors are needed.

    Types of Receptors

    • Intracellular: Located in the cytoplasm or nucleus. Small, hydrophobic ligands.
      • Cytoplasmic receptors
      • Nuclear receptors
    • Cell-surface: Located in the cell membrane. Large, hydrophilic ligands.
      • Ion channel-linked receptors
      • G protein-coupled receptors (GPCRs)
      • Enzyme-linked receptors -Tyrosine kinase -Serine-threonine kinase -Guanylate cyclase
    • (The remaining sections are identical to the original notes.)*

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    Cell Signaling Lecture Notes PDF

    Description

    Test your understanding of homeostasis with this quiz covering key concepts and mechanisms. Explore intercellular communication, cellular responses, and the importance of maintaining stability in multicellular organisms. Ideal for biology students looking to reinforce their knowledge on the topic.

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