Chapter 11: Cell Communication

signal transduction pathway

a series of steps linking a mechanical, chemical, or electrical stimulus to a specific cellular response

cyclic AMP (cAMP)

ring shaped molecule made from ATP that is a common intracellular signaling molecule in eukaryotic cell…regulator of some bacterial operons

inositol trisphosphate (IP3)

second messenger that functions as a intermediate between certain signaling molecules and a subsequent second messenger, Ca2+, by causing a rise in cytoplasmic Ca 2+ concentration

diacylglycerol (DAG)

second messenger produced by the cleavage of the phospholipid PIP2 in the plasma membrane 

scaffolding protein

type of large relay protein to which several other relay proteins are simultaneously attached, increasing efficiency of signal transduction

G Protein

GTP-binding protein that relays signals from a plasma membrane signal receptor known as the G protein-coupled receptor to other signal transduction proteins inside the cell 

chromosome

containing one DNA molecule and associated protein molecules

response (cellular communication)

the change in a specific cellular activity brought about by a tranduced signal from outside the cell

response (feeback regulation)

physiological activity triggered by a change in a variable

adenylyl cyclase

enzyme that converts ATP to cyclic AMP in response to an extracellular signal 

protein kinase

RELAY PROTEIN: enzyme that transfers phosphate groups from ATP to a protein (phosphorylation of protein)

signal transduction

linkage of a mechanical, chemical, or electromagnetic stimulus toa specific cellular response 

second messenger

small, nonprotein, water-soluble molecule or ion (like calcium or AMP) that relays signal to cell’s interior in response to a signaling molecule bounding by a signal receptor protein 

genome

genetic material (complete genes along with noncoding nucleic acid sequences)

chromatin

complex of DNA and proteins that make up chromosomes

G protein-coupled receptor (GPCR)

a ligand (like a neurotransmitter or hormone) binds to the receptor on the outside of the cell.

The receptor activates a G protein inside the cell by swapping GDP for GTP.

The G protein then activates other molecules, such as enzymes or ion channels, starting a signal transduction pathway.

protein phosphatase

RELAY PROTEIN: enzyme removing phosphate groups from protein (reverse of protein kinase)

receptor tyrosine kinase (RTK)

receptor protein spanning the plasma membrane, the cytoplasmic part of which an catalyze the transfer of a phosphate group from ATP to a tyrosine on another protein…

phosphorylation cascade

series of chemical reactions during cell signaling mediated by enzymes in which each kinase in turn phosphorylates and activates another leading to the phosphorylation of many proteins

ligand

molecule that binds specifically to another molecule, usually a larger one

juxtapose signaling

cells touching each other, causing cells to recognize molecules on the adjacent cell (plasmodesmata and gap junctions)

paracrine signaling

one cell releases the signaling molecules affecting nearby cells (short lived)

synaptic signaling

communication with distant cells using nerve cells/neurons; 

neurotransmitter

ligand for synaptic signaling; ex: acetylcholine

endocrine signaling

ligan released by cell and makes it way to the circulatory system (blood) ; spread to entire body; long live (Long-distance signaling)

hormones

secreted by ductless galnds (auxins and THYROXIN, INSULIN, and ADRENALINE)

plasma membrane receptor proteins

binds to water-soluble ligands; G-protein coupled receptors; receptor tyrosine kinases; ion channel receptors

receptor tyrosine kinases

a signaling molecule (like a growth factor) binds to two RTKs, causing them to dimerize (pair up).

the receptors phosphorylate each other on tyrosine residues using ATP.

these phosphate groups serve as binding sites for relay proteins, triggering multiple cell signaling cascades.

ion channel receptors

when a ligand (like a neurotransmitter) binds, the channel opens or closes, allowing ions (Na⁺, K⁺, Ca²⁺, Cl⁻) to flow through.

this causes changes in the cell’s membrane potential and often triggers an electrical or chemical response.

intracellular receptor proteins

found in cytoplasm or nucleus, ligand must be hydrophobic as it has to cross the plasma membrane; ex: steroid, testosterone 

relay protein

amplifies signal all the way to nucleus

apoptosis

controlled cell suicide; prevents damaged cells and enzymes, and morphogenesis ( feet and hand development to separate limbs) 

caspase

When the death signal is received, an

apoptosis-inhibiting protein (Ced-9) is inactivated,

triggering a cascade of caspase proteins that

promote apoptosis