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43 Cards in this Set

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Receptors
(in sensory system) Specialized peripheral ending of afferent neuron, or separate cell intimately associated with it, that detects changes in some aspect of environment; (in intercellular chemical communication) specific binding site in plasma membrane or interior of target cell with which a chemical messenger combines to exert its effects
Specificity
Selectivity; ability of binding site to react with only one, or a limited number of, types of molecules.
Affinity
Strength with which ligand binds to its binding site
Saturation
Occupation of all available binding sites by their ligand
Competition
Ability of similar molecules to combine with the same binding site or receptor.
Antagonists
(drug) molecule that competes with another for a receptor and binds to the receptor but does not trigger the cell’s response. (muscle) muscle whose action opposes intended movement
Agonists
Chemical messenger that binds to receptor and triggers cell’s response; often refers to drug that mimics action of chemical normally in the body.
Down-regulation
Decrease in number of target-cell receptors for a given messenger in response to a chronic high concentration of that messenger
Up-regulation
Increase in number of target-cell receptors for given messenger in response to chronic low extracellular concentration of that messenger.
Supersensitivity
Increased response to a ligand due to receptor up-regulation.
Receptor activation
Change in receptor conformation caused by combination of messenger with receptor.
Signal transduction pathways
Sequence of mechanisms that relay information from plasma-membrane receptor to cell’s response mechanism
Transcription factor
One of a class of proteins that act as gene switches, regulating the transcription of a particular gene by activating or repressing the initiation process.
First messengers
Extracellular chemical messenger
Second messengers
Intracellular substance that serves as relay from plasma membrane to intracellular biochemical machinery, where it alters some aspect of cell’s function.
Protein kinase
Any enzyme that phosphorylates other proteins by transferring to them a phosphate group from ATP.
Tyrosine kinases
Protein kinase that phosphorylates tyrosine portion of proteins; may be part of plasma membrane receptor
Guanylyl cyclase
Enzyme that catalyzes transformation of GTP to cyclic GMP
Cyclic GMP (cGMP)
Cyclic 3’, 5’-guanosine monophosphate; cyclic nucleotide that acts as second messenger in some cells.
cGMP-dependent protein kinase
Enzyme that is activated by cyclic GMP and then phosphorylates specific proteins, thereby altering their activity; also called protein kinase G
JAK kinases
Cytoplasmic kinase bound to a receptor but not intrinsic to it
G proteins
Family of regulatory proteins that reversibly bind guanosine nucleotides; plasma membrane G proteins interact with membrane ion channels or enzymes.
Plasma membrane effector proteins
Plasma-membrane protein that serves as ion channel or enzyme in signal transduction sequence
Adenylyl cyclase
Enzyme that catalyzes transformation of ATP to cyclic AMP
Cyclic AMP (cAMP)
Cyclic 3’, 5’-addenosine monophosphate; cyclic nucleotide that serves as a second messenger for many “first” chemical messengers.
Phosphodiesterase
Enzyme that catalyzes cyclic AMP breakdown to AMP
cAMP-dependent protein kinase
Enzyme that is activated by cyclic AMP and then phosphorylates specific proteins, thereby altering their activity; also called protein kinase A
Phospholipase C
Receptor-controlled plasma-membrane enzyme that catalyzes phosphatidylinositol bisphosphate breakdown to inositol trisphosphate and diacylglycerol.
Diacylglycerol (DAG)
Second messenger that activates protein kinase C, which then phosphorylates a large number of other proteins
Inositol trisphosphate (IP3)
Second messenger that causes release of calcium from endoplasmic reticulum into cytosol.
Protein kinase C
Enzyme that phosphorylates certain intracellular proteins when activated by diacylglycerol
Calmodulin
Intracellular calcium-binding protein that mediates many of calcium’s second-messenger functions
Calmodulin-dependent protein kinases
An intracellular enzyme that, when activated by calcium and the protein calmodulin, phosphorylates many protein substrates within cells; it is a component of many intracellular signaling mechanisms.
Eicosanoids
General term for modified fatty acids that are products of arachidonic acid metabolism (cyclic endoperoxides, prostaglandins, thromboxanes, and leukotrienes; function as paracrine/autocrine agents
Arachidonic acid
Polyunsaturated fatty acid precursor of eicosanoids
Cyclic endoperoxides
Eicosanoid formed from arachidonic acid by cyclooxygenase
Prostaglandins
One class of a group of modified unsaturated fatty acids (eicosanoids); function mainly as paracrine or autocrine agents
Thromboxane A2
Thromboxane that, among other effects, stimulates platelet aggregation in blood clotting
Leukotrienes
Type of eicosanoid that is generated by lipoxygenase pathway and functions as inflammatory mediator
Phospholipase A2
Enzyme that splits arachidonic acid from plasma membrane phospholipids
Cyclooxygenase (COX)
Enzyme that acts on arachidonic acid and initiates production of cyclic endo peroxides, prostalandins, and thromboxanes
Lipoxygenase
Enzyme that acts on arachidonic acid and leads to leukotriene formation
Primary response genes (PRGs)
Gene influenced by transcription factors generated in response to first messengers