Chapter 11 -- Cell Communication

quorum sensing

bacteria secrete detectable molecules, other bacteria sense its concentration-->determine local cell density

biofilm

bacteria attach to a secreted surface after cells reach a certain density

local signaling

signaling b/t adjacent cells

cell-surface molecules

local signaling; done through molecules on cell-surface

growth factors

local signaling; local regulator that stimulates nearby cells to grow and divide

synaptic signaling

local signaling; electric signal triggers a neurotransmitter's molecular secretions

synapse

in local signaling; narrow space b/t a nerve and target cell

long-distance signaling

signaling between non-adjacent cells

hormones

used in long distance signaling; animal and plant cells

endocrine signaling

hormonal long distance signaling; animal

signal transduction pathway

series of changes in difference molecules during signal transduction

ligand

a signal molecule acts as this; a molecule that binds to another, larger molecule

cell-surface transmembrane receptors

used in signal reception; transmembrane proteins embedded into the plasma membrane

G protein-coupled receptor (GPCR)

membrane receptor that binds to a G protein, which binds with GTP

receptor tyrosine kinase (RTK)

protein kinase (phosphorylator); catalyzes a phosphate group from ATP --> protein

ligand-gated ion channel

channel that opens/closes when the ligand changes shape

intracellular receptor

in cytoplasm or nucles; signaling molecule that passes through the plasma membrane
hydrophobic (ie steriod) and/or small

relay molecules

in signal transduction, relays signal from receptor to response

phosphorylation cascade

where a series of different proteins are phosphorylated-->transmits a signal-->shape changep

protein phosphatases

enzymes that quickly remove phosphates from proteins; dephosphorylators

second messengers

small nonprotein water-soluble ions/molecules; diffuse quickly

cyclicAMP

small molecule produced from ATP; second messenger

adenylyl cyclase

ATP --> cAMP from extracellular signal
-adrenaline binds to GPCR
-activates G protein --> activates adenylyl cyclase
-catalyzes synthesis of several cAMP molecules
-another enzyme makes cAMP-->AMP

protein kinase A

activated by increase in cAMP levelq

IP3 and DAG

2nd messengers that help with Ca2+ release
produced by a phospholipid in the plasma membrane

scaffolding proteins

large relay proteins to which several other relay proteins are attached
present with others in large, permanently held together networks
enhances speed and accuracy of the cellular response

apoptosis

programmed 'cell-suicide' when a cell is infected/damaged/at end of its functional life span
-initiated by activation of cell death genes
-cellular agents chop up DNA and fragment the cellular components
-cell shrinks and becomes lobed

ced-3 and ced-4

key apoptosis inducing genes; usually present in inactive form

ced-9

in the outer mitochondrial membrane; when death signal received, ced-9 disables its 'brake' on apoptosis