AP Biology Cell Signaling Flashcards

9025303879	homeostasis	steady internal state/maintenance of internal balance	0
9025303880	cells communicate directly via...	cell junctions	1
9025303881	cells become different because _________ varies among cells.	gene expression	2
9025303882	what is the major factor that influences which genes will be expressed?	environment	3
9025303883	what types of signals can the cell sense?	chemical and physical	4
9025303884	where do external signals come from?	biological sources (pathogen, bee sting), physical sources (light, heat), and other cells	5
9025303885	juxtacrine signaling	signaling between cells in direct contact with each other	6
9025303886	gap junctions	in animal cells, these junctions allow ions and small molecules to pass quickly	7
9025303887	plasmodesmata	in plant cells, these are tunnels of cytoplasm between cells that allow movement of ions, amino acids, sugars, small proteins, and microRNA	8
9025303888	synaptic signaling	local electrochemical signaling occurring between nerve cells or nerve and muscle cells	9
9025303889	neurotransmitters	short-lived chemical signals that play a key role in synaptic signaling	10
9025303890	paracrine signaling	local communication; cells secrete substances that affect only nearby cells, like growth factors during early animal development	11
9025303891	endocrine signaling	long-distance communication; distributes signals throughout a multicellular organism (hormones)	12
9025303892	signal transduction pathway	series of steps by which a signal on a cell's surface is converted to a specific cellular response	13
9025303893	three stages of cell signaling	reception, transduction, response	14
9025303894	step 1 of cell signaling: reception	a ligand from outside the cell binds to a receptor protein and the receptor changes shape	15
9025303895	step 2 of cell signaling: transduction	series of molecule interactions that relay signals from receptor to target molecule, typically within the cell	16
9025303896	step 3 of cell signaling: response	the specific cellular response to the signal molecule, usually transcription or cytoplasmic activities	17
9025303897	ligand	signaling molecule	18
9025303898	location of receptors	within the cell and on the plasma membrane	19
9025303899	intracellular receptors	inside the cell; found in the cytoplasm or nucleus. the ligand must be hydrophobic/nonpolar/very small	20
9025303900	membrane receptors	anchored to the cell membrane. the ligand is water-soluble/hydrophilic/polar/large	21
9025303901	second messengers	molecules inside the cell that relay signals from the receptor to the target molecule	22
9025303902	protein kinase	enzyme that phosphorylates and activates proteins at the next level	23
9025303903	phosphorylation	the addition of a phosphate group, usually to active a molecule or transfer energy	24
9025303904	phosphorylation cascade	a reaction that enhances and amplifies a signal	25
9025303905	apoptosis	controlled cell suicide, where the cell is systematically dismantled and digested, protecting neighboring cells from damage	26
9025303906	autocrine signaling	signals diffuse from one part of a cell to another part of the same cell	27
9025303907	sequence of a signal transduction pathway	signal (1st messenger) >>> receptor >>> proteins or other 2nd messengers >>> cellular responses	28
9025303908	if a ligand is HYDROPHOBIC, what type of receptor will it bind to?	intracellular	29
9025303909	if a ligand is HYDROPHILIC, what type of receptor will it bind to?	membrane	30
9025303910	when a ligand binds to a receptor, what happens to the receptor?	it changes shape, initiating some sort of response	31
9025303911	receptor proteins	molecules with binding sites for signaling molecules (ligands)	32
9025303912	gated ion channel receptors	transmembrane protein with a gated channel that opens and closes in response to a specific signal; when open, a specific ion can pass through	33
9025303913	ligand-gated ion receptor	a ligand, or molecular signal, triggers the channel to open/close to allow an ion to pass	34
9025303914	voltage-gated ion receptor	open or close in response to voltage differences across a membrane	35
9025303915	typical ligand-gated ion sequence	signal received >>> ligand binds to receptor >>> receptor changes shape >>> channel opens and ions pass >>> ions initiate chemical response inside cell >>> ligand detaches from receptor and deactivates channel	36
9025303916	what can cause a ligand to detach from a receptor?	ligand can be broken down by an enzyme, binding site can be blocked by an allosteric ligand, or the ion passage can be obstructed by a channel blocker	37
9025303917	example of a ligand-gated ion channel	an active neuron releases acetylcholine (Ach) into synapse >>> Ach binds to ligand-gated receptor molecule of next neuron >>> receptor molecules open >>> Na+ enters cell >>> inside of cell becomes more positive >>> change in voltage initiates a nerve impulse	38
9025303918	example of a voltage-gated ion channel	after Ach binds and Na+ enters the cytoplasm, the voltage inside the neuron becomes more positive. if strong enough, voltage-gated ion channels for Na+ and then K+ will open, allowing the impulse to travel along the neuron.	39
9025303919	G-protein coupled receptor (GPCR)	a transmembrane protein that activates a G protein, which in turn activates another membrane protein, which triggers a cell response or activates a second messenger	40
9025303920	why is a G-protein receptor called that?	it has a GTP or a GDP attached to it instead of ATP or ADP (the difference is guanine instead of adenine)	41
9025303921	typical G-protein coupled receptor sequence	ligand binds to receptor and it changes shape >>> receptor uses GTP to activate G protein >>> G protein binds to effector protein >>> effector is activated >>> effector initiates response >>> GTP is converted to GDP >>> receptor is deactivated	42
9025303922	protein kinase receptors	transmembrane protein that is a kinase (enzyme that adds phosphate groups to a protein)	43
9025303923	protein kinase receptors are most important in...	cell reproduction and regulation	44
9025303924	G-protein coupled receptors are most important in...	most things - it is the largest family of signal receptors and includes vision, taste, airborne signals, hormones, neurotransmitters, immune system	45
9025303925	types of cell surface receptors	ion channel receptors, G-protein coupled receptors, and protein kinase receptors	46
9025303926	ion channel receptors are most important in...	muscle contraction and nerve impulses	47
9025303927	best understood protein kinase receptor	receptor tyrosine kinase (RTK)	48
9025303928	typical protein kinase receptor sequence	ligand binds to receptor >>> receptor forms a dimer with another receptor >>> the receptors phosphorylate each other and activates the complex >>> relay protein attaches to receptor and is phosphorylated >>> relay proteins are released >>> relay proteins activate cellular response	49
9025303929	how is a protein kinase receptor deactivated?	dephosphorylation of kinases OR when the membrane folds and encircles the receptor protein in a vesicle (endocytosis)	50
9025303930	examples of protein kinase receptor signaling pathways	insulin signaling and mitogen-activated protein kinases (MAPK)	51
9025303931	examples of hydrophobic chemical messengers for intracellular/cytoplasmic receptors	steroid hormones (testosterone, estrogen), thyroid hormones, nitric oxide gas (NO), second messengers	52
9025303932	typical intracellular receptor signaling pathway	ligand enters cytoplasm >>> ligand binds to and activates receptor in cytoplasm or nucleus >>> complex acts as a transcription factor, binding to DNA and affecting gene expression	53
9025303933	how is an intracellular receptor signaling pathway deactivated?	ligand or receptor proteins are enzymatically degraded	54
9025303934	second messenger	molecules that relay a signal from the inside face of the receptor protein to other molecules that may initiate a cellular response or may act as additional second messengers	55
9025303935	characteristics of a second messenger	small, nonprotein, and hydrophilic/hydrophobic/gaseous	56
9025303936	cascade effect/signaling cascade	a series of enzymatic reactions where a small number of enzymes can activate more and more to initiate a large-scale response	57
9025303937	scaffold proteins	improve efficiency of a signaling cascade by holding enzymes involved in close proximity - keeps members of one signaling cascade isolated from others	58
9025303938	protein phosphatase	dephosphorylates a substrate (removes a phosphate group to deactivate it)	59
9025303939	characteristics of signaling pathways	characterized by a signal, transduction, and a response. highly specific and regulated. one signal molecule can cause a cascade effect, releasing thousands inside the cell. these pathways evolved millions of years ago in a common ancestor.	60
9025303940	advantages of signaling pathways	amplification (widespread), control (very accurate), and multiplicity (a single signaling molecule can activate many different pathways)	61