Unit I – Signal Transduction Study Notes

Flashcards focusing on key terms and concepts related to signal transduction, homeostasis, and receptor mechanisms.

Homeostasis

The process by which organisms maintain a near-constant internal environment despite changes in the external environment.

Negative Feedback

A feedback mechanism where the response opposes the original stimulus to maintain stability.

Positive Feedback

A feedback mechanism where the response amplifies the stimulus, often leading to a more dramatic change.

Signal Transduction

The conversion of an extracellular signal into a cellular response.

Ligand-Gated Ion Channels

Receptors that allow ions to flow into the cell when a ligand binds, resulting in a fast response.

G-Protein Coupled Receptors (GPCRs)

A large family of cell surface receptors that utilize G proteins to transmit signals inside the cell.

Receptor Tyrosine Kinases (RTKs)

A class of membrane receptors that, upon ligand binding, undergo dimerization and autophosphorylation.

Calcium & Calmodulin

Calcium acts as a second messenger, and Calmodulin binds Ca²⁺ to activate various enzymes.

Cholera Toxin

An exotoxin from Vibrio cholerae that locks Gαs in an active state, leading to elevated cAMP and severe diarrhea.

Pertussis Toxin

A toxin from Bordetella pertussis that locks Gαi in an inactive state, preventing inhibition of adenylyl cyclase.

cAMP

Cyclic adenosine monophosphate, a second messenger that mediates various signaling pathways.

Phospholipase C (PLC)

An enzyme that cleaves PIP₂ into DAG and IP₃, playing a key role in signaling pathways.

Insulin Receptor

A receptor that acts as a tyrosine kinase, playing a critical role in glucose uptake and metabolism.

Nicotinic Acetylcholine Receptors

Ligand-gated ion channels found at neuromuscular junctions, mediating rapid synaptic transmission.

G Protein

A heterotrimeric protein that transmits signals from GPCRs to other cellular effectors.

Second Messenger

A molecule that transmits signals inside the cell after the binding of an extracellular signal to a receptor.