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):
1

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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2

Growth Factors 

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

3

Paracrine signaling 

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

  • local signaling

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4

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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5

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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6

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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7

Ligand 

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 

 

 

8

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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9

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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10

Transcription factors

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

  • Receptors act as transcription factors that turn on other genes 

11

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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12

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

13

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

14

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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