LE 3 CELLMOL 11/11

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Questions and Answers

What is the type of chemical signaling that a macrophage uses to communicate with itself?

Autocrine

What type of chemical signaling is involved when a cell releases a signal that travels through the bloodstream to reach distant target cells?

Endocrine

What chemical messenger is also known as adrenaline?

Epinephrine

Norepinephrine is derived from the amino acid tyrosine.

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

What type of chemical messenger is insulin?

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

What does the term 'ligand' refer to in the context of chemical signaling?

<p>Any molecule that binds to a specific receptor</p> Signup and view all the answers

Which of the following describes a receptor with a high affinity for its ligand?

<p>The receptor will bind to the ligand easily even at low concentrations. (C)</p> Signup and view all the answers

What is the term for the constant needed for the ligand to separate from a receptor?

<p>Dissociation Constant (Kd)</p> Signup and view all the answers

Which type of drug binds to receptors and activates them, mimicking the action of natural ligands?

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

What term describes the process by which a cell reduces its sensitivity to a particular ligand by decreasing the number of receptors on its surface?

<p>Receptor down-regulation</p> Signup and view all the answers

What is the term for the process that removes extracellular messenger molecules from the environment, effectively ending the signal?

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

What type of protein is involved in desensitizing a G protein-coupled receptor (GPCR) by adding a phosphate group?

<p>G protein-coupled receptor kinase (GRK)</p> Signup and view all the answers

The term 'amplification' in cell signaling refers to the ability of a single receptor to activate multiple downstream molecules, resulting in a cascade effect.

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

What is the second messenger produced when epinephrine binds to a beta-adrenergic receptor?

<p>Cyclic AMP (cAMP)</p> Signup and view all the answers

What enzyme catalyzes the conversion of ATP to cyclic AMP?

<p>Adenylyl cyclase</p> Signup and view all the answers

What enzyme breaks down cyclic AMP into its inactive linear form?

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

What is the primary target molecule of cyclic AMP in the cell?

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

What is the major protein responsible for the breakdown of glycogen in the liver?

<p>Glycogen phosphorylase</p> Signup and view all the answers

What are the two main categories of the central nervous system?

<p>Sympathetic and parasympathetic</p> Signup and view all the answers

Which neurotransmitter is primarily released by the parasympathetic nervous system?

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

Which of the following is NOT a catecholamine?

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

What is the primary target molecule of epinephrine in the heart?

<p>Beta-adrenergic receptor</p> Signup and view all the answers

What is the main effect of epinephrine binding to alpha-1 adrenergic receptors in smooth muscle cells?

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

What is the primary function of the enzyme phospholipase C (PLC) in cell signaling?

<p>Cleaving phosphatidylinositol 4,5-bisphosphate (PIP2) into diacylglycerol (DAG) and inositol 1,4,5-trisphosphate (IP3)</p> Signup and view all the answers

What is the role of calcium in smooth muscle contraction?

<p>Calcium binds to calmodulin, activating myosin light chain kinase (MLCK), which phosphorylates myosin, leading to muscle contraction.</p> Signup and view all the answers

What is the function of the sodium-calcium antiporter in maintaining calcium homeostasis in the cell?

<p>The sodium-calcium antiporter pumps calcium out of the cell against its concentration gradient, using the energy harnessed from the inward movement of sodium ions.</p> Signup and view all the answers

What type of protein is often associated with calcium to activate various downstream targets in the cell?

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

What are the two main types of G proteins that are often associated with GPCRs?

<p>Gs and Gi</p> Signup and view all the answers

The Ras pathway is activated by the binding of a ligand to a receptor tyrosine kinase (RTK)?

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

What is the role of the protein SOS in the Ras pathway?

<p>SOS acts as a guanine nucleotide exchange factor (GEF), facilitating the exchange of GDP with GTP on Ras, activating the Ras protein.</p> Signup and view all the answers

What protein is responsible for turning off the Ras pathway by promoting the hydrolysis of GTP back to GDP?

<p>GAP (GTPase-activating protein)</p> Signup and view all the answers

What is the primary effect of the activated Ras pathway in the cell?

<p>Promoting cell growth and proliferation</p> Signup and view all the answers

What is the role of the protein kinase Akt in the PI-3 kinase signaling pathway?

<p>Akt promotes cell survival and proliferation by inhibiting apoptosis and activating cell growth pathways.</p> Signup and view all the answers

What is the name of the protein complex that is often targeted for degradation in the absence of Wnt proteins?

<p>APC-axin-GSK3 complex</p> Signup and view all the answers

What is the primary role of the Wnt pathway in cell development?

<p>Wnt signaling is essential for proper development and tissue regeneration, regulating cell fate decisions, cell proliferation, and cell-cell interactions.</p> Signup and view all the answers

What is the difference between the receptors that typically interact with steroid hormones and the receptors that interact with many other signaling molecules?

<p>Steroid hormone receptors are typically intracellular, whereas most other signaling molecules bind to receptors on the cell surface.</p> Signup and view all the answers

What is the role of scaffold proteins in signal transduction pathways?

<p>Scaffold proteins serve as a platform to bring together different signaling molecules, organizing them into a functional complex and enhancing the efficiency and specificity of signal transduction.</p> Signup and view all the answers

Flashcards

Signal Transduction

The process by which cells communicate with each other using chemical messengers.

Juxtacrine Signaling

Cells connected by gap junctions communicate by passing chemical signals directly.

Paracrine Signaling

Cells that are close but not directly connected communicate by releasing nearby chemical signals.

Endocrine Signaling

Cells communicate over long distances by releasing chemical signals (hormones) into the bloodstream.

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Autocrine Signaling

A cell releases a chemical signal that affects itself.

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Epinephrine

A hormone also known as adrenaline, involved in the fight-or-flight response.

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Norepinephrine

A hormone involved in the fight-or-flight response, similar to epinephrine.

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Tyrosine

An amino acid that is a precursor to epinephrine and norepinephrine.

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Thryoxine

A hormone made from tyrosine, important for metabolism.

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Antidiuretic Hormone

A peptide hormone that helps regulate fluid balance in the body.

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Receptor Affinity

The strength of the interaction between a ligand and its receptor.

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High Affinity

A receptor binds strongly to a ligand, even at low concentrations.

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Low Affinity

A receptor binds weakly to a ligand, requiring high concentration to activate effectively.

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Dissociation Constant (Kd)

The concentration of ligand required for half of the receptors to be occupied.

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Receptor Down-Regulation

A decrease in the number of receptors in response to prolonged exposure to a ligand.

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Agonist

A drug that mimics the action of a natural ligand, activating the receptor.

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Antagonist

A drug that blocks the action of a natural ligand, preventing receptor activation.

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G-protein coupled receptor (GPCR)

A type of cell surface receptor that employs a G-protein to initiate a downstream signaling cascade.

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G protein

A protein that acts as a molecular switch to relay signals from a cell surface receptor to intracellular enzymes or channels.

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cAMP

Cyclic AMP; a second messenger that often mediates the effects of G protein-coupled receptors.

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Protein Kinase A

An enzyme that adds phosphate groups to other proteins in response to activation by cAMP.

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Glycogenolysis

The breakdown of glycogen into glucose monomers.

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Gluconeogenesis

The synthesis of new glucose from non-carbohydrate sources.

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CREB

cAMP response element-binding protein, a transcription factor that regulates gene expression in response to cAMP.

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Study Notes

Cell Biology and Molecular Biology

  • Course Instructor: Dr. Esperanza Chua Cabrera
  • Coverage: All topics
  • Grade Consultation: Dec 6
  • Exam time: 10

Signal Transduction: Chemical Messengers

  • Signal types: Autocrine, juxtacrine, paracrine, endocrine

  • Autocrine: Target cell is the same as the signaling cell.

  • Juxtacrine: Target cell is connected by gap junctions to the signaling cell.

  • Paracrine: Target cell is near the signaling cell.

  • Endocrine: Signaling molecule travels through the bloodstream to distantly located cells.

  • Endocrine hormones:

    • Amino acid derivatives: Epinephrine, norepinephrine, thyroxine
    • Peptides: ADH (vasopressin).
    • Proteins: Insulin, glucagon
    • Steroids: Androgens, estrogens, corticosteroids
    • Local mediators: Histamine

  • Chemical signaling based on the target size and distance covered by the signal.

Receptor Affinity

  • High affinity: Receptors occupied at low ligand concentrations; rapid binding
  • Low affinity: Receptors occupied at high ligand concentrations; slower binding

Receptor Down-Regulation

  • Cells adapt to constant ligand exposure by reducing receptor numbers.
  • Receptor-mediated endocytosis: internalizes receptors, reducing their exposure
  • Example: experiencing a new perfume scent, you get used to it over time
  • The more ligand present, the more response; the receptors will adapt and require higher concentrations of ligand for the same response.

Signaling Pathway Summary

  • Signal transduction is a series of steps that convert a signal into a cellular response.
  • There are different types of ligands.
  • Receptors are proteins that specifically bind to signals.
  • The signal binding triggers changes in the receptor.

Different Types of Ligands

  • Molecules that trigger specific cellular responses.

Activation of Protein Kinase A (PKA)

  • cAMP binds to regulatory subunits, causing them to detach from catalytic subunits.
  • Catalytic subunits become active and phosphorylate target proteins.
  • This leads to various cellular responses.

Cyclic AMP (cAMP)

  • A second messenger molecule involved in signal transduction pathways.
  • cAMP is produced from ATP by adenylyl cyclase.
  • cAMP activates PKA.
  • cAMP is degraded to AMP by cAMP phosphodiesterase.

Summary of Cell Signaling

  • Review different signaling pathways, ligands, receptors, and downstream processes
  • Understanding how cells respond to external signals and how to regulate these responses
  • Summary of how the ligand binds to the receptor, and the various steps in signalling pathways.

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Cell Biology and Molecular Biology - LE3_ CELLMOL PDF
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