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16 Cards in this Set
- Front
- Back
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List and explain the different forms of intercellular signaling
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Contact dependent:
Membrane-bound or via gap junctions Paracrine or autocrine: Between different cell types or same cell type Cells in close vicinity -Synaptic: Fast & selective, synapse -Endocrine: Bloodstream, slow, long distances |
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How can a receptor can be down-regulated?
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via endocytosis and lysosome digestion
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Give exaples of two chemical signals that can diffuse through the membrane and bind cytosolic receptors or to receptors that are in the nucleus
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NO and CO
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Small hydrophobic signaling molecules bind with nuclear receptors that act as _________ ________ stimulationg ________ of target genes
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transcription factors
transcription |
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Outline the action of G protein-linked receptors
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Upon binding of signal molecule, the conformation of receptor changes
Upon excessive stimulation the receptor may be down regulated. In turn it alters conformation of alpha-subunit GDP exchanges for GTP Two active components alpha and beta-gamma are liberated and interact with target proteins in the plasma membrane |
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Outline the action of the enzyme-linked receptor, tyrosine kinases
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1. ligand binding
2. receptor oligomerization or dimerization 3. conformational change 4. autophosphorylation chain activates kinase activity of receptor 5. phosphorylated tyrosine become binding sites for other signaling proteins 6. the bound proteins may become phosphorylated or just activated by binding |
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Outline the action of G protein-linked receptors
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Upon binding of signal molecule, the conformation of receptor changes
Upon excessive stimulation the receptor may be down regulated. In turn it alters conformation of alpha-subunit GDP exchanges for GTP Two active components alpha and beta-gamma are liberated and interact with target proteins in the plasma membrane |
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Understand the What's the importance of phosphorylation?
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It's an intracellular communication and regulation mechanism and common scheme of enzyme activation.
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Shat do kinases and phosphatases do?
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kinase = enz that adds a phosphate
phosphatase = enz that removes a phosphate |
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Exchange of _____ to ______is a common motif to turn on signals.
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GDP, GTP
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Explain the mechanism of cAMP as a secondary messenger.
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Secondary messengers like cAMP are used to transfer the effects of hormones like glucagon and adrenaline, which cannot pass through the cell membrane.
Specifically, it activates protein kinases such as PKA (protein kinase A) |
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Outline the example of cAMP as a secondary messenger discussed in class (PKA).
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1. signal molecule activates G-protein receptor
2. receptor activates the G-protein 3. Activated G-protein alpha subunit binds to and activates ADENYLYL CYCLASE 4. Adenylyl cyclase converts ATP to cAMP (secondary messenger) 5. cAMP activates PKA 6. PKA diffuses through the nuclear membrane and activates, via phosphorylation, the CREB 6. CBP binds to CREB and activates transcription of the target gene |
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Using the example discussed in class, describe how Ca2+ acts as a secondary messenger.
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Essentially, Ca2+ acts as a signal transducer between IP3 and protein kinase C (PKC)
A signal binds a G-protein-linked receptor The activated alpha subunit activates phospholipase C-beta Which cleaves an inositol phospholipid to generate diacylglycerol and IP3 IP3 activates Ca2+ channel in ER and causes Ca2+ eflux into cytosol Diacyglycerol together with Ca2+ recruits protein kinase C (PKC) form cytosol and activates it |
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Briefly describe the RAS mechanism as a secondary messenger.
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RAS is an intracellular signalling protein.
RAS is activated when an extracellular receptor is activated by a tyrosine kinase and, in turn, triggers the binding of a Grb-2 adaptor protein to the receptor and then then a Ras GEF protein to the Grb-2 protein. The Ras GEF then activates the inactive Ras protein by exchaning GDP for GTP. The activated RAS then initiates a phosphorylation cascade resulting in cell proliferation. |
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Intracellular signalling pathways have the potential for ________ and _______.
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branching, amplification
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Intracellular interpretation of chemical signals is ______, and can lead to many _______ end results in the cell
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complex, different
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