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BIOLOGY - CLUTCH
CH.11 - CELL SIGNALING
CONCEPT: CELL SIGNALING
Cell signaling is how cells communicate with molecules, and involves three steps:
Reception – a ligand binds to a receptor protein, effecting some change in the protein
□ Receptors only bind specific ligands
Transduction – a series of proteins and other molecules interact with each other, as a result of ligand-receptor binding
□ The molecules involved in transduction vary based on the cell
Response – the cell carries out some function as a result of the signal transduction pathway □ A cell’s response to a signal depends on the cell’s receptors and signal transduction pathways
EXAMPLE:
BIOLOGY - CLUTCH
CH.11 - CELL SIGNALING
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CONCEPT: CELL SIGNALING
● Cells in multicellular organisms communicate through cell junctions and cell recognition.
EXAMPLE:
● Cells communicate through paracrine and endocrine signaling.
EXAMPLE:
BIOLOGY - CLUTCH
CH.11 - CELL SIGNALING
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CONCEPT: CELL SIGNALING
● Cells communicate through synaptic signaling.
EXAMPLE:
● Unicellular organisms in a population communicate with one another.
□ Quorum sensing – signaling in microbes related to population density.
EXAMPLE:
BIOLOGY - CLUTCH
CH.11 - CELL SIGNALING
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CONCEPT: RECEPTION
● G protein-coupled receptors (GPCR) active G proteins to transmit signals.
EXAMPLE:
● Receptor tyrosine kinases (RTK) can activate multiple signal transduction pathways.
□ Kinase – an enzyme that transfers a phosphate group to its substrate, energizing it, or to ADP to form ATP.
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BIOLOGY - CLUTCH
CH.11 - CELL SIGNALING
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CONCEPT: RECEPTION
● Ligand-gated ion channels open is response to ligand binding.
EXAMPLE:
● Small and lipid soluble molecules can readily pass through the membrane, into cells, to reach intracellular receptors.
□ Transcription factors – proteins that control gene expression
EXAMPLE:
BIOLOGY - CLUTCH
CH.11 - CELL SIGNALING
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CONCEPT: SIGNAL TRANSDUCTION
Signal transduction is carried out by proteins and secondary messengers.
□ Secondary messengers are signaling molecules that cells use to effect changes.
● Phosphorylation cascades activate and deactivate a series of proteins through the transfer of phosphate groups.
□ Kinases transfer phosphate groups to their substrates
□ Phosphatases remove phosphate groups from their substrates
EXAMPLE:
BIOLOGY - CLUTCH
CH.11 - CELL SIGNALING
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CONCEPT: SIGNAL TRANSDUCTION
● cAMP functions as a secondary messenger in GPCR signal transduction.
□ Adenylyl cyclase is activated by a G protein, and converts ATP into cAMP
EXAMPLE:
● Ca2+ is a widely used secondary messenger, and is stored in the lumen of the endoplasmic reticulum.
□ A G protein activates phospholipase C to cleave PIP2 into IP3 and DAG. IP3 acts as a ligand for Ca2+ channels.
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BIOLOGY - CLUTCH
CH.11 - CELL SIGNALING
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CONCEPT: SIGNAL TRANSDUCTION
● Signal cascades can result in signal amplification.
EXAMPLE:
● Scaffolding proteins connect and regulate members of a pathway in complexes.
EXAMPLE: ● Crosstalk – signaling pathways interact with each other to modify cellular response.
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BIOLOGY - CLUTCH
CH.11 - CELL SIGNALING
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CONCEPT: SIGNAL RESPONSE
Response to signaling generally comes as a change in:
□ Protein activity – turning proteins on, off, or modulating their activity
□ Gene expression – turning genes on or off, or changing the rates of proteins synthesis
□ Cell division – preparing the cell for division, and causing the process to occur
EXAMPLE:
● Apoptosis is programmed cell death.
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BIOLOGY - CLUTCH
CH.11 - CELL SIGNALING
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