Signaling & Communication in Cells. Basic Key Vocabulary. homeostasis: organisms maintain a stable level or condition at the cellular and whole-organism level
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homeostasis: organisms maintain a stable level or condition at the cellular and whole-organism level
receptor: site on cell that is activated by a stimulus; presence of stimulus alone is not enough for a response; receptor must match the signal
signal/stimulus: hormones, population size, light, heat, chemicals
- chemical signals are called ligands
signal transduction pathway: sequence of events at molecular level that result in a cell’s response to a signal at its receptor
autocrine: affect same cell that releases it; example: cancer cells affecting their own rate of cell division
(no distance: remember the immune system example where touching cells transmitted information)
paracrine (short distance): travel via diffusion to nearby cells; example: neurotransmitters going from nerve cell to next nerve cell
hormones (long distance): travel via circulation to distant cells; example: thyroid stimulating hormone produced by pituitary gland in brain stimulates thyroid in neck to produce thyroid hormone, which affects metabolism in all other body tissues
Example: The sight, smell and taste of food can cause the vagus nerve to release the neurotransmitter acetylcholine, which binds to receptors on parietal cells, causing an influx of calcium ions that activate intracellular phosphokinase enzymes; this in turn results in the activation of a proton pump to expel hydrogen ions, which can then combine with chloride ions to form the hydrochloric acid that is required for the digestion of food in the stomach.
allosteric regulation: protein’s shape is altered when a molecule binds somewhere other than the active site (remember, this is non-competitive inhibition)
- example: ligand-gated channel
- Example: atropine blocks acetylcholine from binding and can be used to counter nerve gas effects (nerve gas alters the activity of the enzyme that controls acetylcholine)
Cocaine and amphetamines inhibit the re-uptake of dopamine. Cocaine is a dopamine transporter blocker that competitively inhibits dopamine uptake to increase the presence of dopamine.
- example: acetylcholine neurotransmitter binding to receptor triggers influx of Na+, which eventually leads to contraction of muscle
Protein kinase receptors (change shape): binding initiates a reaction chain to occur on cytoplasmic side of cell
G protein-linked receptors:ligand binding to receptor causes receptor to bind to G protein on cytoplasmic side; G protein binding activates effector protein
… signal transduction pathways or signaling cascades.
- either expose the active site (activate) or cover it (inhibit)