Cell Signaling – Flashcards
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Signal Transduction Pathway
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A series of steps linking a mechanical or chemical stimulus to a specific cellular response
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Signal Transduction
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The linkage of a mechanical, chemical or electromagnetic stimulus to a specific cellular response.
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Paracrine Signaling
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local signaling
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Synaptic Signaling
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Occurs in the animal nervous system. An electrical signal along a nerve cell triggers the secretion of a chemical signal carried by neurotransmitter molecules. These diffuse across a synapse. The neurotransmitter stimulates the target cell.
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both animals and plants use chemicals called ____ for long-distance signaling.
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Hormones
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Reception
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Reception is the target cell's detection of a signaling molecule coming from outside the cell. A chemical signal is "detected" when the signaling molecule binds to a receptor protein located at the cell's surface or inside the cell.
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Transduction
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The binding of the signaling molecule changes the receptor protein in some way, initiating the process of transduction. The trasduction stage converts the signal to a form that can bring about specific cellular response. transduction sometimes occurs in a single step but more often requires a sequence of changes in a series of different molecules- a signal transduction pathway.
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Response
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The 3rd stage of cell signaling, the transduced signal finally triggers a specific cellular response. The response may be almost any imaginable cellular activity. The cell-signaling process helps ensure that crucial activities like these occur in the right cells, at the right time and in proper coordination with the other cells of the organism.
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3 Stages of Cellular Conversation
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Reception
Transduction
Response
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Ligand
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a molecule that specifically binds to another molecule. Ligand binding generally cause a receptor protein to undergo a change in shape.
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In signal transduction, binding of the ligand alters ____________.
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The ability of the receptor to transmit the signal.
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Most signal receptors are _______.
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Plasma membrane proteins.
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G protein-coupled receptor
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A plasma membrane receptor that work with the help of a G protein. they have 7 helices spanning the membrane. It functions as a molecular switch that is either on or off. when activated it causes GTP to displace GPD, activating the G protein
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Tryrosine Kinases
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plasma membrane receptors that attach phosphates to tyrosines.
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Each activated protein in the Tyrosine kinase receptor process triggers a _____ leading to a cellular response.
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Transduction pathway
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On receptor tyrosin kinase complex may activate ___________ different transduction pathways & cellular responses.
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10 or more
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A key difference in G protein-coupled receptors and tyrosine kinase receptors is
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the ability of a single lingand-ginding event in the tyrosine kinase complex to trigger so many transduction pathways.
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Ligan-gated ion channel
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a type of membrane receptor containing a region that can act as a "gate" when the receptor changes shape. Eg. Na+ , neurotransmitter released at synapses bind ligands to ion channels.
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Where is the hormone receptor complex located when a hormone firsts binds with it?
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In the cytoplasm
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What happens once a hormone binds with the receptor complex?
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It enters the nucleus & binds with specific genes.
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The bound protein in the hormone receptor complex acts as a transcription factor, stimulating ______
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the transcription of the gene into mRNA.
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Intercellular receptor proteins are found in either _______.
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the cytoplasm or nucleus of target cells.
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The signal transduction pathway can be thought of as _______.
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Falling dominoes, the signal-activated receptor activates another molecule, which activates yet another molecule, and so on.
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Protein Kinase
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the enzyme that transfers phosphate groups from ATO to a protein
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Protein phosphatases
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enzymes that can rapidly remove phosphate groups from proteins, dephosphorylation
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Second messengers
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small, nonprotein, water-soluble molecules or ions
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Because second messengers are both small and water-soluble, they can _______.
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readily spread throughout the cell by diffusion.
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Benefits of multistep pathway in transduction
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*it greatly amplifies the signal
*It provides more opportunities for coordination and regulation than simpler systems do
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How is phosphorylation useful in signaling?
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It changes a protein from an inactive form to an active form
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What is true of transcription factors?
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They control which genes are expressed
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The toxin of Vibrio cholerae causes profuse diarrhea because it
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modifies a G protein involved in regulating salt and water secretion.
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Phosphorylation cascades involving a series of protein kinases are useful for cellular signal transduction because
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they amplify the original signal manyfold.
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Lipid-soluble signal molecules, such as testosterone, cross the membranes of all cells but affect only target cells because
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intracellular receptors are present only in target cells.
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Up to 60% of all medicines used today exert their effects by influencing what structures in the cell membrane?
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G proteins
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Binding of a signaling molecule to which type of receptor leads directly to a change in distribution of ions on opposite sides of the membrane?
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ligand-gated ion channel
