Week 3 (Exam 1): Intro to Homeostasis, Endocrine System; Human Reproductive Cycles Flashcards
g protein-coupled receptors
a large family of cell-surface molecules composed of a single polypeptide chain w/ 7 transmembrane spanning regions; when activated, they associate with a G protein
how fast are cellular responses to the activation of a G protein-coupled receptor?
rapid
what did G protein-coupled receptors evolve from?
sensory receptors in unicellular eukaryotes
when are G protein-coupled receptors inactive?
in the absence of a ligand, and when it is bound to GDP
when are G protein-coupled receptors active?
when they are bound to a ligand, and when it is bound to GTP
what components are G proteins made up of?
alpha, beta, and gamma subunits
first step of the activation of G protein by a G protein-coupled receptor
when the alpha subunit is bound to GDP, the 3 subunits are joined together & G protein is inactive
second step of the activation of G protein by a G protein-coupled receptor
G protein associates w/ an activated receptor; GDP is released by GTP; beta & gamma subunits separate
third step of the activation of G protein by a G protein-coupled receptor
activated alpha subunit binds to & activates a target protein —> cell response
second messenger
an intermediate, cytosolic signaling molecule that transmits signals from a receptor to a target within the cell
first messenger
transmits signals from outside the cell to a receptor
first step of adrenaline signaling in heart muscle
activated adenylyl cyclase converts ATP into the 2nd messenger cAMP, which activates protein kinase A
second step of adrenaline signaling in heart muscle
activated protein kinase A phosphorylates proteins in the heart muscle, causing heart rate to increase
binding affinity
the tightness of the binding between the receptor & the signaling molecule
first step of termination
adrenaline detaches from the receptor, inactivating the receptor
second step of termination
an activated G protein deactivates itself by converting GTP to GDP
third step of termination
enzymes in the cytosol degrade to cAMP, which stops the phosphorylation & activation of target proteins by PKA
fourth step of termination
phosphatases remove phosphate groups from proteins, causing them to become inactive
homeostasis
the active regulation & maintenance of a stable internal physiological state in the face of a changing external environment
negative feedback
a process in which the output or product of a pathway opposes the initial stimulus, so that steady conditions are maintained
set point
a steady-state value in homeostatic regulation
thermoregulation
the ability to maintain a constant body temperature
endocrine system
a system of cells & glands that secretes hormones into the bloodstream & works w/ the nervous system to regulate an animal’s internal physiological functions
hormones
a chemical signal that influences physiology & development in both plants & animals; in animals, hormones are released into the bloodstream & circulate throughout the body
