Cell Signaling Mechanisms and Hormones
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Questions and Answers

What triggers bioluminescence in Vibrio fischeri?

  • High levels of carbon dioxide in the environment
  • Absence of nutrients
  • Binding of autoinducers to luxR receptor proteins (correct)
  • Release of hormones from other cells

Which of the following best describes quorum sensing?

  • Communication between cells through direct contact
  • Signaling that occurs only in animals
  • A process that only occurs in bacteria that do not produce autoinducers
  • Chemical signaling based on the population density of cells (correct)

What role do calcium ions play in cellular signaling?

  • They inhibit the synthesis of proteins
  • They function as secondary messengers (correct)
  • They only transport signals across the synapse
  • They act as primary messengers

Which type of hormone is insulin classified as?

<p>Protein hormone (A)</p> Signup and view all the answers

What is the primary function of neurotransmitters?

<p>To facilitate communication between neurons and effector cells (A)</p> Signup and view all the answers

Which of the following is an example of a cytokine?

<p>Interleukin (A)</p> Signup and view all the answers

What is a characteristic feature of amine hormones?

<p>They are derived from amino acids. (D)</p> Signup and view all the answers

How do hormones typically reach their target cells?

<p>Via the bloodstream after being secreted by endocrine glands (A)</p> Signup and view all the answers

What role does the sodium potassium pump play in neurons?

<p>It maintains resting potential. (C)</p> Signup and view all the answers

What is the resting potential of a neuron at equilibrium?

<p>-70mV (D)</p> Signup and view all the answers

How many sodium ions are transported out of the cell during one cycle of the sodium potassium pump?

<p>3 (B)</p> Signup and view all the answers

What initiates the conformational change in the sodium potassium pump?

<p>The hydrolysis of ATP. (C)</p> Signup and view all the answers

What is the function of sodium-dependent glucose cotransporters?

<p>They link sodium movement to glucose uptake. (A)</p> Signup and view all the answers

What happens to sodium ions during the process of glucose transport into epithelial cells?

<p>They are actively pumped out of the cells. (C)</p> Signup and view all the answers

What is the energy source required for the sodium potassium pump to function?

<p>ATP (D)</p> Signup and view all the answers

What happens to potassium ions once they bind to the sodium potassium pump?

<p>They are moved into the cell. (A)</p> Signup and view all the answers

How does facilitated diffusion differ from active transport in glucose transport mechanisms?

<p>Facilitated diffusion is passive, while active transport requires energy. (B)</p> Signup and view all the answers

What causes the sodium-dependent glucose cotransport protein to change shape?

<p>The attachment of sodium and glucose. (B)</p> Signup and view all the answers

What is the primary role of GPCR proteins in cell signaling?

<p>Transmitting signals via secondary messengers (C)</p> Signup and view all the answers

Which of the following describes the action of insulin in the body?

<p>It leads to the phosphorylation of intracellular proteins. (D)</p> Signup and view all the answers

What differentiates steroid hormones like testosterone from peptide hormones like epinephrine?

<p>Steroid hormones can cross the plasma membrane. (A)</p> Signup and view all the answers

What mechanism is illustrated by the role of oxytocin during childbirth?

<p>Positive feedback (C)</p> Signup and view all the answers

Which type of neurotransmitter is characterized as chains of amino acids?

<p>Peptide neurotransmitters (C)</p> Signup and view all the answers

What initiates the cascade of reactions within a cell following the binding of a signaling chemical to a protein receptor?

<p>Dissociation of G protein subunits (A)</p> Signup and view all the answers

How does progesterone primarily act in the body after ovulation?

<p>By thickening the endometrium (C)</p> Signup and view all the answers

What is the function of nitric oxide (NO) as a neurotransmitter?

<p>It causes rapid vasodilation in blood vessels. (A)</p> Signup and view all the answers

What is the significance of the hydrophobic section of transmembrane receptor proteins?

<p>It facilitates the passage of lipophilic signals. (B)</p> Signup and view all the answers

What occurs when an extracellular ligand binds to a GPCR?

<p>GDP is released and replaced by GTP. (A)</p> Signup and view all the answers

Which type of receptors are known to directly influence gene transcription?

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

What defines negative feedback in physiological systems?

<p>Restoration of homeostasis (A)</p> Signup and view all the answers

What crucial role do tyrosine kinase receptors play in cellular processes?

<p>They phosphorylate themselves and other proteins. (D)</p> Signup and view all the answers

Which mechanism allows oestradiol to affect the secretion of gonadotropin-releasing hormones?

<p>Indirectly through positive feedback (B)</p> Signup and view all the answers

Flashcards

Quorum Sensing

Cell-to-cell communication based on population density in bacteria.

Autoinducers

Chemical messengers produced and released by bacteria during quorum sensing.

Protein Receptors

Binding sites on cells with specific shapes for signals.

Hormones

Chemical messengers secreted in bloodstream for communication.

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Neurotransmitters

Chemical messengers released by neurons for communication.

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Cytokines

Chemical messengers of the immune system, regulating immune cells.

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Secondary Messengers

Intracellular signaling molecules triggered by external signals.

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Epinephrine

An amine hormone, a chemical messenger derived from amino acids.

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Resting Potential

The electrical charge difference across the neuron's cell membrane when it is not sending a signal. This difference is usually around -70mV, maintained by the sodium-potassium pump.

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Amino Acid Neurotransmitters

Neurotransmitters made up of single amino acids, like glutamate and GABA.

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Sodium-Potassium pump

A protein pump that actively transports sodium ions out of the cell and potassium ions into the cell. This pump requires energy (ATP) to function.

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Peptide Neurotransmitters

Neurotransmitters made up of chains of amino acids, like endorphins and oxytocin.

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Amine Neurotransmitters

Neurotransmitters derived from modified amino acids, like dopamine and serotonin.

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Sodium-Potassium Pump Function

To maintain resting potential in neurons by moving sodium ions out and potassium ions into the axon, creating the electrochemical imbalance necessary for action potential.

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Facilitated Diffusion

The passive movement of glucose molecules from the small intestine into epithelial cells through specialized protein channels. This process doesn't require energy.

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Nitrous Oxide Neurotransmitters

Neurotransmitters made up gases like NO and N2O, involved in various functions.

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Sodium-Dependent Glucose Cotransporters

Proteins that help move glucose against its concentration gradient (from low concentration to high concentration) into epithelial cells, using the energy from the movement of sodium ions down its concentration gradient.

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Natural Selection in Signaling

The evolutionary process where organisms with advantageous signaling molecules are more likely to survive and reproduce.

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Indirect Active Transport

A type of transport where the movement of one molecule against its concentration gradient is indirectly fueled by the use of ATP to create a concentration gradient for another molecule.

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Diversity of Signaling Roles

The wide variety of functions that chemical signals perform in the body, leading to different types of signaling molecules.

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Cotransport

A type of transport where the movement of one molecule down its concentration gradient is coupled with the movement of another molecule against its concentration gradient.

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Transmembrane Receptor Protein

A protein embedded in the cell membrane, with a specific binding site for a ligand outside the cell.

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Active Transport

The movement of molecules across a cell membrane against their concentration gradient (from low to high concentration). This process requires energy.

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Intracellular Receptor Protein

A protein located inside the cell (cytoplasm or nucleus) that binds to hydrophobic ligands.

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Transduction Pathway Initiation

The process of initiating a series of cellular responses upon ligand binding to a receptor protein.

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Concentration Gradient

Difference in concentration of a molecule across a membrane, driving the movement of molecules from a high concentration area to a low concentration area.

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ATP

Adenosine triphosphate, the primary energy currency of cells that fuels many cellular processes.

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ACH Receptor

A protein that binds acetylcholine (ACH), causing sodium channels to open and trigger nerve impulses.

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G Protein

A protein complex linked to transmembrane receptors, activated by ligand binding, and involved in signaling pathways.

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G Protein Activation

The process where a ligand binding to a GPCR changes its shape, releasing GDP and replacing it with GTP, activating the G protein.

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Epinephrine's Action Mechanism

Epinephrine binds to a GPCR, activates a G protein, triggers cAMP production, and initiates cellular responses.

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Tyrosine Kinase Receptors

Transmembrane receptors with tyrosine kinase activity, activated by ligand binding, and initiating phosphorylation cascades.

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Insulin's Action

Insulin binding to its receptor initiates a phosphorylation cascade, leading to glucose transporter activation and glucose uptake by cells.

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Study Notes

Cell Signaling Mechanisms

  • Ligands are specific signaling chemicals that bind to receptors, initiating a response.
  • Protein receptors have specific shapes (binding pockets) to allow ligands to bind.
  • Quorum sensing is a form of cell-to-cell communication based on population density.
  • Quorum refers to a group or population of similar organisms.
  • Vibrio fischeri are bioluminescent bacteria, only emitting light when their population density reaches a critical level, triggering quorum sensing. They release autoinducers, chemical messengers, into their environment. Increasing population density leads to higher autoinducer concentrations. Binding to receptors initiates a cascade of reactions ultimately leading to bioluminescence.

Chemical Signaling in Animals

  • Hormones are chemical messengers secreted by endocrine glands into the bloodstream, travelling to target cells to bind to receptors (surface or intracellular). Examples include epinephrine, insulin, oestradiol, progesterone, and testosterone.
  • Neurotransmitters are chemical messengers released by neurons into synapses, facilitating communication between neurons and cells like muscles and glands. Acetylcholine is an example.
  • Cytokines are chemical messengers vital for cell-to-cell communication in the immune system. They regulate immune cell development, activation, and behavior.
  • Calcium ions act as secondary messengers in a wide array of cellular processes stored intracellularly or entering through gated channels. They trigger events like muscle contractions and neurotransmitter release.

Different Types of Signaling Molecules

  • Hormones:
    • Amine hormones: Derived from amino acids (modified). Examples include epinephrine.
    • Protein hormones: Large peptide chains. Examples include insulin, follicle-stimulating hormone (FSH), & luteinizing hormone (LH).
    • Steroid hormones: Lipid-derived. Examples include oestradiol, progesterone, and testosterone.
  • Neurotransmitters: Subdivided into amino acid, peptide, amine, and nitrous oxide classifications.

Receptor Types

  • Transmembrane receptors: Integral proteins in the plasma membrane. Hydrophilic ligands bind to the outside, while the inside is hydrophobic.
  • Intracellular receptors: Located in the cytoplasm or nucleus. Hydrophobic ligands diffuse through the membrane to bind intracellularly.

Initiation of Transduction Pathways

  • Binding of a signal molecule to a receptor triggers a cascade of intracellular reactions.
  • Transmembrane receptors: initiate intracellular cascades.
  • Intracellular receptors: initiate changes in gene expression.

Receptor Examples

  • Acetylcholine (ACH) receptors: Binds to voltage-gated sodium channels, allowing sodium influx to propagate nerve impulses.
  • G protein-coupled receptors (GPCRs): The largest class in humans.
    • Activation: Ligand binding changes GPCR shape, activating a G protein that releases GDP, binds GTP, and separates into subunits. The activated subunits interact with secondary messengers and initiate cascades.
  • Epinephrine Action: Acts on GPCRs — which lead to cAMP generation, triggering a metabolic change.
  • Tyrosine kinase receptors: Activate kinase enzymes, leading to phosphorylation cascades. Typically bind proteins via phosphorylation.
    • Insulin Action: Binds to TK receptors triggering glucose uptake through phosphorylation.
  • Steroid hormone action: Direct gene regulation by binding to intracellular receptors, leading to changes in gene transcription. (ex: testosterone, oestradiol, progesterone)

Feedback Mechanisms

  • Positive feedback: Amplifies a response. Example: Oxytocin release during childbirth.
  • Negative feedback: Counteracts a response to maintain homeostasis. Example: Temperature regulation by the body.

Cell Membrane Transport

  • Sodium-Potassium pumps: Maintain resting potential and indirectly regulate other transport mechanisms.
  • Glucose transport: Includes facilitated diffusion and sodium-dependent glucose cotransporters which utilise sodium gradients.

Other Key Concepts

  • Secondary messengers: Small molecules that amplify and relay signals inside a cell (e.g., cAMP).
  • Phosphorylation: The addition of a phosphate group to a molecule, often changing its activity.
  • Gene expression: The process by which a gene is used to create its protein product.

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Description

This quiz explores the fascinating world of cell signaling mechanisms, including how ligands and receptors interact and the role of quorum sensing in bacteria like Vibrio fischeri. Additionally, it covers chemical signaling in animals through hormones and their pathways. Test your knowledge on these crucial biological concepts.

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