Diagram the steps common to signal transduction pathways correct answers extracellular signal molecule
v
receptor protein
v
intracellular signaling proteins
v
effector proteins
Describe the major classes of signaling molecules and how signal characteristics affect receptor location correct...
MMG 409 Exam 2(Correctly solved)
Diagram the steps common to signal transduction pathways correct answers extracellular signal molecule
v
receptor protein
v
intracellular signaling proteins
v
effector proteins
Describe the major classes of signaling molecules and how signal characteristics affect receptor location correct answers see next cards
Contact-dependent signaling correct answers requires cells to be in direct membrane-
membrane contact
- signaling cell has a membrane-bound signal molecule
- important for development and in immune responses
Paracrine Signaling correct answers depends on LOCAL MEDIATORS that are released into the extracellular space and act on neighboring cells
- autocrine signaling: cells produce signals that they also respond to (ex: cancer cells)
Synaptic Signaling correct answers signaling is performed by neurons that transmit signals electrically along their axons and release NEUROTRANSMITTERS at synapses
which are often far away from the cell body
Endocrine Signaling correct answers depends on endocrine cells, which secrete HORMONES into the bloodstream for distribution throughout the body
Explain how the receptor binds a signal correct answers signal binding requires a ligand
in a simple reversible reaction.
Why is Kd important? correct answers The dissociation/equilibrium constant. It is a measure of the affinity (or tightness of binding) of the receptor for its ligand
Kd=Koff/Kon correct answers - If Kon is bigger than Koff then the ligand binds faster than the complex dissociates
- The faster Kon is in comparison to Koff, the higher the affinity and lower the Kd
- The lower the Kd, the higher the affinity between a ligand and its receptor
Ion-Channel Coupled Receptors correct answers - rapid synaptic signaling between nerve cells and other electrically excitable cells (nerve or muscle cells)
- mediated by NEUROTRANSMITTERS that turn them on/off
G-Protein Couple receptors correct answers - regulate the activity of enzymes or ion-
channels - G-PROTEIN mediates the interaction
- changes the concentration of one or more small intracellular signaling molecules (enzymes) or ion permeability (ion-channels)
Enzyme-Couple Receptors correct answers - function as enzymes or associated with enzymes
- activate catalytic domain or associated enzyme
- majority are protein kinases which phosphorylate specific sets of proteins in the target cell when activated
3 main types of molecular on/off switches correct answers 1. Second messengers
2. Phosphorylation
3. Gtp-binding proteins
Second Messengers correct answers small chemicals that act as intracellular signaling molecules
- ex: cyclic AMP and Ca++: water-soluble and diffuse in cytosol
- ex: DAG: lipid-soluble, diffuse in plasma membrane
- Pass the signal on by binding to and altering the behavior of selected signaling or effector proteins
Phosphorylation correct answers - Protein kinases: adds phosphate groups to amino acid on signaling protein
- Protein Phosphatase: removes phosphate groups
ex: serine/threonine kinase and tyrosine kinase
GTP-binding proteins correct answers active = GTP-bound
inactive = GDP-bound
GAP: drives protein into inactive state
GEF: drives protein into active state
Major characteristics of a G-protein coupled receptor correct answers - largest family of cell-surface receptors
- mediate responses to signals like hormones, neurotransmitters, and local mediators.
- single peptide chain that threads back and forth across the lipid bilayer 7 times, forming a cylindrical structure, often with a deep ligand-binding site at its center.
Explain how and why G-proteins are tethered to the plasma membrane correct answers How: alpha and gamma subunits have covalently attached lipid molecules that help them bind to the plasma membrane, and the alpha-subunit has GDP bound. Why: must be tethered to receive signal molecules from the GPCR. this allows GDP to detach so that a GTP can attach and activate the G-protein.
Cholera toxin correct answers enzyme that catalyzes the transfer of ADp ribose from intracellular NAD+ to the alpha-subunit of Gs
- remains active and stimulates adenylyl cyclase forever
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