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Flashcards in Kapitel 15 Deck (116)
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Adjustment of sensitivity following repeated stimulation. The mechanism that allows a cell to react to small changes in stimuli even against a high background level of stimulation.

adaptation (desensitization)


General term for a protein that functions solely to link two or more different proteins together in an intracellular signaling pathway or protein complex. (Figure 15–11)

adaptor protein - adaptor


Membrane-bound enzyme that catalyzes the formation of cyclic AMP from ATP. An important component of some intracellular signaling pathways.

adenylyl cyclase (adenylate cyclase)


Serine/threonine protein kinase that acts in the PI-3-kinase/Akt intracellular signaling pathway involved especially in signaling cells to grow and survive. Also called protein kinase B (PKB).



Member of a family of proteins that contributes to GPCR desensitization by preventing the activated receptor from interacting with G proteins and serving as an adaptor to couple the receptor to clathrin-dependent endocytosis. (Figure 15–42)



Plant hormone - commonly indole-3-acetic acid - with numerous roles in plant growth and development.



Multifunctional cytoplasmic protein involved in cadherin-mediated cell–cell adhesion - linking cadherins to the actin cytoskeleton. Can also act independently as a transcription regulatory protein. Has an important role in animal development as part of a Wnt signaling pathway.

beta-catenin (β-catenin)


Class of steroid signal molecules in plants that regulate the growth and differentiation of plants throughout their life cycle via binding to a cell-surface receptor kinase to initiate a signaling cascade.



Serine/threonine protein kinase that is activated by Ca2+/calmodulin. Indirectly mediates the effects of an increase in cytosolic Ca2+ by phosphorylating specific target proteins. (Figure 15–33)

Ca2+/calmodulin-dependent kinase (CaM-kinase)


Ubiquitous intracellular Ca2+-binding protein that undergoes a large conformation change when it binds Ca2+ - allowing it to regulate the activity of many target proteins. In its activated (Ca2+-bound) form - it is called Ca2+/calmodulin. (Figure 15–33)



Multifunctional Ca2+/calmodulin-dependent protein kinase that phosphorylates itself and various target proteins when activated. Found in most animal cells but is especially abundant at synapses in the brain - and is involved in some forms of synaptic plasticity in vertebrates. (Figure 15–34)

CaM-kinase II


Member of the Rho family of monomeric GTPases that regulate the actin and microtubule cytoskeletons - cell-cycle progression - gene transcription - and membrane transport.



Internal cyclical process that produces a particular change in a cell or organism with a period of around 24 hours - for example the sleep-wakefulness cycle in humans.

circadian clock


Photoreceptor cell in the vertebrate retina that is responsible for color vision in bright light.

cone photoreceptor (cone)


Form of intercellular signaling in which signal molecules remain bound to the surface of the signaling cell and influence only cells that contact it.

contact-dependent signaling


Transcription regulator that recognizes the cyclic AMP response element (CRE) in the regulatory region of genes activated by cAMP. On activation by PKA - phosphorylated CREB recruits a transcriptional coactivator (CREB-binding protein; CBP) to stimulate transcription of target genes.

CRE-binding (CREB) protein


Plant flavoprotein sensitive to blue light. Structurally related to blue-light-sensitive enzymes called photolyases (involved in the repair of ultraviolet-induced DNA damage) but do not have a role in DNA repair. Also found in animals - where they have an important role in circadian clocks.



Latent transcription regulator that mediates the effects of Hedgehog.

Cubitus interruptus (Ci)


Nucleotide that is generated from ATP by adenylyl cyclase in response to various extracellular signals. It acts as a small intracellular signaling molecule - mainly by activating cAMP-dependent protein kinase (PKA). It is hydrolyzed to AMP by a phosphodiesterase. (Figure 15–25)

cyclic AMP (cAMP)


Specific enzyme that rapidly and continuously destroys cyclic AMP - forming 5′-AMP. (Figure 15–25).

cyclic AMP phosphodiesterase


Enzyme that phosphorylates target proteins in response to a rise in intracellular cyclic AMP. (Figure 15–26)

cyclic AMP-dependent protein kinase (protein kinase A - PKA)


Nucleotide that is generated from GTP by guanylyl cyclase in response to various extracellular signals.

cyclic GMP (cGMP)


Specific enzyme that rapidly hydrolyzes and degrades cyclic GMP.

cyclic GMP phosphodiesterase


Cell-surface receptor that binds a specific cytokine or hormone and acts through the JAK–STAT signaling pathway. (Figure 15–56)

cytokine receptor


Enzyme activated by certain cell-surface receptors (tyrosine-kinase-associated receptors) that transmits the receptor signal onward by phosphorylating target cytoplasmic proteins on tyrosine side chains.

cytoplasmic tyrosine kinase


Single-pass transmembrane signal protein displayed on the surface of cells that binds to the Notch receptor protein on a neighboring cell - activating a contact-dependent signaling mechanism.



see adaptation



Lipid produced by the cleavage of inositol phospholipids in response to extracellular signals. Composed of two fatty acid chains linked to glycerol - it serves as a small signaling molecule to help activate protein kinase C (PKC). (Figure 15–28)

diacylglycerol (DAG)


Scaffold protein recruited to the Frizzled family of cell-surface receptors upon their activation by Wnt binding that helps relay the signal to other signaling molecules.



Specialized animal cell that secretes a hormone into the blood. Usually part of a gland - such as the thyroid or pituitary gland.

endocrine cell