Cell Receptors and Transduction Pathways Flashcards Preview

AP Biology 2014 > Cell Receptors and Transduction Pathways > Flashcards

Flashcards in Cell Receptors and Transduction Pathways Deck (14):

Cell junctions in plants and animals 

Directly connect the cytoplams of adjacent cells 

  • Animals: gap junctions 
  • Plants: plasmodesmata 

--> signaling substances in the cytosol can pass freely between adjacent cells 

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Growth Factors 

Class of local regulators that stimulate nearby target cells to grow and divide 


Paracrine signaling 

Multiple cells recieve and respond to a signal sent by one cell 

  • local signaling

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Synaptic Signaling 

One cell receives and responds to a signal sent directly to that cell 

  • Occurs in animal nervous system
  • Electric signal moving along a nerve cell triggers the secretion of neurotransmitter molecules carrying a chemical signal
  • Molecules diffuse across a synapse (space between nerve cell and target cell)--> triggers a response in the cell  


  • local signaling 

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Endocrine signaling 

Hormonal signaling, long distance 

Cells release hormones that travel via the circulatory system to responsive target cells in other parts of the body 

  • Plant hormones travel mostly through vascular tissue (xylem / phloem), but some travel through air as gas
  • Common animal hormone: epinephrine 

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Three stages of cell signaling

  1. Reception- target cell’s detection of a signaling molecule coming from outside the cell 
  2. Transduction- a step or series of steps that converts the signal that causes a specific cellular response 
  3. Response- transduced signal triggers cellular response 

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A molecule that specifically binds to another molecule, usually causing the receptor to change shape, which activates the receptor 

  • Signaling molecules generally act as ligands to receptor proteins on target cells 




G protein-coupled receptor (GPCR)

A cell surface transmembrane receptor that makes use of a G protein (protein that binds GTP)

  • After receptor protein binds and changes shape, its cytoplasmic side binds and activates a G protein
  • Activated G protein carries a GTP molecule
  • Leaves the receptor, diffuses along the membrane, and then binds to an enzyme that triggers the rest of the reaction

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Ligand-gated ion channel 

A membrane receptor that has a region that can act as a “gate” for ions when the receptor assumes a certain shape 

  • Regulates passage of specific ions across membrane
  • Example: sodium potassium pump 

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Transcription factors

Proteins that control which genes are turned on / transcribed into mRNA 

  • Receptors act as transcription factors that turn on other genes 


Steroid hormone

Chemical messenger that passes through the cell membrane to reach a receptor 

  • Hydrophobic (nonpolar) enough to cross the cell membrane
  • Example: testosterone

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Protein kinase

An enzyme that transfers phosphate groups from ATP to a protein

  • Participates in signaling pathways in animals, plants, and fungi
  • Many relay molecules in signal transduction pathways are protein kinases, often acting on other protein kinases in the pathway


Protein phosphatases

Enzymes that quickly remove phosphate groups from proteins (dephosphorylation)

  • By dephosphorylating and thus inactivating protein kinases, phosphates turn off the signal transduction pathway when the initial signal is no longer present


Second messengers

Small, nonprotein water-soluble (polar) molecules or ions involved in signaling pathways

  • Small size allows them easily spread throughout the body by cell division 
  • Calcium Ions 
    • ​A signal relayed by a signal transduction pathway may trigger an increase in calcium in the cytosol
  • Cyclic AMP
    • Epinephrine binds to the plasma membrane of a liver cell, heightening the cytosolic concentration of cAMP
    • cAMP broadcasts signal to cytoplasm
    • Does not exist for long without the hormone because another enzyme converts cAMP back to AMP

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