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</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.</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</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</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</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</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

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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